// file      : doc/testscript.cli
// license   : MIT; see accompanying LICENSE file

"\name=build2-testscript-manual"
"\subject=Testscript language"
"\title=Testscript Language"

// NOTES
//
// - Maximum <pre> line is 70 characters.
//

"
\h0#preface|Preface|

This document describes the \c{build2} Testscript language. It starts with a
discussion of the motivation behind a separate domain-specific language for
running tests and then introduces a number of Testscript concepts with
examples. The remainder of the document provides a more formal specification
of the language, including its integration into the build system, conceptual
model and execution, lexical structure, as well as syntax and semantics. The
final chapter describes the testing guidelines and the Testscript style as
used in the \c{build2} project itself.

In this document we use the term \i{Testscript} (capitalized) to refer to the
Testscript language. Just \i{testscript} means code written in this language.
For example: \"We can pass additional information to testscripts using
target-specific variables.\" Finally, \c{testscript} refers to the file name.

We also use the equivalent distinction between \i{Buildfile} (language),
\i{buildfile} (code), and \c{buildfile} (file).

\h1#intro|Introduction|

The \c{build2} \c{test} module provides the ability to run an executable
target as a test along with passing options and arguments, providing the
\c{stdin} input, as well as comparing the \c{stdout} output to the expected
result. For example:

\
exe{hello}: file{names.txt}: test.stdin = true
exe{hello}: file{greetings.txt}: test.stdout = true
exe{hello}: test.options   = --greeting 'Hi'
exe{hello}: test.arguments = - # Read names from stdin.
\

This works well for simple, single-run tests. If, however, our testing
required multiple runs with varying inputs and/or analyzing output,
traditionally, we would resort to using a scripting language, for instance
Bash or Python. This, however, has a number of drawbacks. Firstly, this
approach is not portable (there is no Bash or Python on Windows \i{out of the
box}). It is also hard to write concise tests in a general-purpose scripting
language. The result is often a test suite that has grown incomprehensible
with everyone dreading adding new tests. Secondly, it is hard to run such
tests in parallel without major effort. Usually this involves having a
separate script for each test and implementing some kind of a test harness.

Testscript is a domain-specific language for running tests. It vaguely
resembles Bash and is optimized for concise test description and fast
execution by focusing on the following functionality:

\ul|

\li|Supplying input via command line and \c{stdin}.|

\li|Comparing to expected exit status.|

\li|Comparing \c{stdout}/\c{stderr} to expected output, including
    using regex.|

\li|Setup/teardown commands and automatic file/directory cleanups.|

\li|Simple (single-command) and compound (multi-command) tests.|

\li|Test groups with common setup/teardown.|

\li|Test isolation for parallel execution.|

\li|Portable POSIX-like builtins subset.|

\li|Test documentation.||

Note that Testscript is a \i{test runner}, not a testing framework for a
particular programming language. It does not concern itself with how the test
executables themselves are implemented. As a result, it is mostly geared
towards functional testing but can also be used for unit testing if external
input/output is required. Testscript is part of the \c{build2} build system
and is implemented by its \c{test} module.

As a quick introduction to the Testscript's capabilities, let's \i{properly}
test a \"Hello, World\" program. For a simple implementation the corresponding
\c{buildfile} might look like this:

\
exe{hello}: cxx{hello}
\

We also assume that the project's \c{bootstrap.build} loads the \c{test}
module which implements the execution of testscripts.

To start, we create an empty file called \c{testscript}. To indicate that a
testscript file tests a specific target we simply list it as a target's
prerequisite, for example:

\
exe{hello}: cxx{hello} testscript
\

Let's assume our \c{hello} program expects us to pass the name to greet as a
command line argument. And if we don't pass anything, it prints an error
followed by usage and terminates with a non-zero exit code. We can test
this failure case by adding the following line to the \c{testscript} file:

\
$* 2>- != 0
\

While it sure is concise, it may look cryptic without an explanation. When the
\c{test} module runs tests, it passes to each testscript the path to the
target of which this testscript is a prerequisite. So in our case the
testscript will receive the path to our \c{hello} executable. The buildfile
can also pass along additional options and arguments (see \l{#integration
Build System Integration} for details). Inside the testscript, all of this
(target path, options, and arguments) are bound to the \c{$*} variable. So, in
our case, if we expand the above line, it would be something like this:

\
/tmp/hello/hello 2>- != 0
\

Or, if we are on Windows, something like this:

\
C:\projects\hello\hello.exe 2>- != 0
\

The \c{2>-} redirect is the Testscript equivalent of \c{2>/dev/null} that is
both portable and more concise (\c{2} here is the \c{stderr} file
descriptor). If we don't specify it and our program prints anything to
\c{stderr}, then the test fails (unexpected output).

The remainder of the command (\c{!= 0}) is the exit status check. If we don't
specify it, then the test is expected to return zero exit code (which
is equivalent to specifying \c{== 0}).

If we run our test, it will pass provided our program behaves as expected.
One thing our test doesn't verify, however, is the diagnostics that gets
printed to \c{stderr} (remember, we ignored it with \c{2>-}). Let's fix that
assuming this is the code that prints it:

\
cerr << \"error: missing name\" << endl
     << \"usage: \" << argv[0] << \" <name>\" << endl;
\

In Testscript you can compare output to the expected result for both
\c{stdout} and \c{stderr}. We can supply the expected result as either a
\i{here-string} or \i{here-document}, both which can be either literal or
regex. The here-string approach works best for short, single-line output and
we will use it for another test in a minute. For this test let's use the
here-document since the expected diagnostics has two lines:

\
$* 2>>EOE != 0
error: missing name
usage: hello <name>
EOE
\

Let's decrypt this: the \c{2>>EOE} is a here-document redirect with \c{EOE}
(stands for End-Of-Error) being the string we chose to mark the end of the
here-document fragment. Next comes the here-document fragment followed by the
end marker.

Now, when executing this test, the \c{test} module will check two things: it
will compare the \c{stderr} output to the expected result using the \c{diff}
tool and it will make sure the test returns a non-zero exit code. Let's give
it a go:

\
$ b test
testscript:1:1: error: hello stderr doesn't match expected
  info: stderr: test-hello/1/stderr
  info: expected stderr: test-hello/1/stderr.orig
  info: stderr diff: test-hello/1/stderr.diff
--- test-hello/1/stderr.orig
+++ test-hello/1/stderr
@@ -1,2 +1,2 @@
 error: missing name
-usage: hello <name>
+usage: /tmp/hello/hello <name>
\

While not what we hoped for, at least the problem is clear: the program name
varies at runtime so we cannot just hardcode \c{hello} in our expected output.
How do we solve this? The best fix would be to use the actual path to the
target; after all, we know it's the first element in \c{$*}:

\
$* 2>>\"EOE\" != 0
error: missing name
usage: $0 <name>
EOE
\

You can probably guess what \c{$0} expands to. But did you notice another
change? Yes, those double quotes in \c{2>>\"EOE\"}. Here is what's going on:
similar to Bash, single-quoted strings (\c{'foo'}) are taken literally while
double-quoted ones (\c{\"foo\"}) have variable expansions, escaping, and so
on. In Testscript this semantics is extended to here-documents in a curious
way: if the end marker is single-quoted then the here-document lines are taken
literally and if it is double-quoted, then there can be variable expansions,
etc. An unquoted end marker is treated as single-quoted (note that this is
unlike Bash where here-documents always have variable expansions).

This example illustrated a fairly common testing problem: output variability.
In our case we could fix it perfectly since we could easily calculate the
varying part exactly. But often figuring out the varying part is difficult if
not outright impossible. A good example would be a system error message based
on the \c{errno} code, such as file not being found. Different C runtimes can
phrase the message slightly differently or it can be localized. Worse, it can
be a slightly different error code, for example \c{ENOENT} vs \c{ENOTDIR}.

To handle output variability, Testscript allows us to specify the expected
output as a regular expression. For example, this is an alternative fix to our
usage problem that simply ignores the program name:

\
$* 2>>~/EOE/ != 0
error: missing name
/usage: .+ <name>/
EOE
\

Let's explain what's going here: to use a regex here-string or here-document
we add the \c{~} \i{redirect modifier}. In this case the here-document end
marker must start and end with the regex introducer character of your choice
(\c{/} in our case). Any line inside the here-document fragment that begins
with this introducer is then treated as a regular expression rather than a
literal (see \l{#syntax-regex Output Regex} for details).

While this was a fairly deep rabbit hole for a first example, it is a good
illustration of how quickly things get complicated when testing real-world
software.

Now that we have tested the failure case, let's test the normal functionality.
While we could have used a here-document, in this case a here-string will be
more concise:

\
$* 'World' >'Hello, World!'
\

It's also a good idea to document our tests. Testscript has a formalized test
description that can capture the test \i{id}, \i{summary}, and \i{details}.
All three components are optional and how thoroughly you document your tests
is up to you.

The description lines precede the test command. They start with a colon
(\c{:}), and have the following layout:

\
: <id>
: <summary>
:
: <details>
: ...
\



The recommended format for \c{<id>} is \c{<keyword>-<keyword>...} with at
least two keywords. The id is used in diagnostics, to name the test working
directory, as well as to run individual tests. It can only contain
alphanumeric characters as well as underscores, pluses, and minuses. The
recommended style for \c{<summary>} is that of the \c{git(1)} commit summary.
The detailed description is free-form. Here are some examples (\c{#} starts a
comment):

\
# Only id.
#
: missing-name
$* 2>>\"EOE\" != 0
...

# Only summary.
#
: Test handling of missing name
...

# Both id and summary.
#
: missing-name
: Test handling of missing name
...

# All three: id, summary, and a detailed description.
#
: missing-name
: Test handling of missing name
:
: This test makes sure the program detects that the name to greet
: was not specified on the command line and both prints usage and
: exits with non-zero code.
...
\

The recommended way to come up with an id is to distill the summary to its
essential keywords by removing generic words like \"test\", \"handle\", and so
on. If you do this, then both the id and summary will convey essentially the
same information. As a result, to keep things concise, you may choose to drop
the summary and only have the id (this is what we often do in \c{build2}
tests). If the id is not provided, then it will be automatically derived from
the line number in testscript (we have already seen one in the earlier failed
test diagnostics).

Either the id or summary (but not both) can alternatively be specified inline
in the test command after a colon (\c{:}), for example:

\
$* 'World' >'Hello, World!' : command-name
\

Similar to handling output, Testscript provides a convenient way to supply
input to the test's \c{stdin}. Let's say our \c{hello} program recognizes the
\c{-} argument as an instruction to read the names from \c{stdin}. This is how
we could test this functionality:

\
$* - <<EOI >>EOO : stdin-names
Jane
John
EOI
Hello, Jane!
Hello, John!
EOO
\

As you might suspect, we can also use here-strings to supply \c{stdin}, for
example:

\
$* - <'World' >'Hello, World!' : stdin-name
\

Let's say our \c{hello} program has a configuration file that captures custom
name-to-greeting mappings. A path to this file can be passed with the \c{-c}
option. To test this functionality we first need to create a sample
configuration file. This calls for a multi-command or \i{compound} test, for
example:

\
cat <<EOI >=hello.conf;
John = Howdy
Jane = Good day
EOI
$* -c hello.conf 'Jane' >'Good day, Jane!' : config-greet
\

Notice the semicolon (\c{;}) at the end of the first command: it indicates
that the following command is part of the same test.

Other than that, you may be wondering what exactly is \c{cat}? While most
POSIX systems will have a program with this name, there is no such thing, say,
on vanilla Windows. To help with portability Testscript provides a subset
(both in terms of the number and supported features) of POSIX utilities, such
as, \c{echo}, \c{touch}, \c{cat}, \c{mkdir}, \c{rm}, and so on (see
\l{#builtins Builtins} for details).

You may also be wondering why we don't have a third command, such as \c{rm},
that removes \c{hello.conf}? It is not necessary because this file will be
automatically registered for cleanup that happens at the end of the test. We
can also register our own files and directories for automatic cleanup. For
example, if the \c{hello} program created the \c{hello.log} file on
unsuccessful runs, then this is how we could have cleaned it up:

\
$* ... &hello.log != 0
\

What if we wanted to run two tests for this configuration file functionality?
For example, we may want to test the custom greeting as above but also make
sure the default greeting is not affected. One way to do this would be to
repeat the \c{cat} command in each test. But there is a better way: in
Testscript we can combine related tests into groups. For example:

\
: config
{{
  conf = $~/hello.conf

  +cat <<EOI >=$conf
  John = Howdy
  Jane = Good day
  EOI

  $* -c $conf 'John' >'Howdy, John!' : custom-greet
  $* -c $conf 'Jack' >'Hello, Jack!' : default-greet
}}
\

A test group is an \c{{{}-style scope that contains several tests. Variables
set inside a scope (like our \c{conf}) are only in effect until the end of
this scope. Groups can also perform common, non-test actions with \i{setup}
and \i{teardown} commands. The setup commands start with the plus sign (\c{+})
and must come before the tests while teardown \- with minus (\c{-}) and must
come after the tests.

Note that setup and teardown commands are not part of any test (notice the
lack of \c{;} after \c{+cat}), rather they are associated with the group
itself. Their automatic cleanup only happens at the end of the scope (so our
\c{hello.conf} will only be removed after all the tests in the group have
completed).

A scope can also have a description. In particular, assigning a test group an
id (\c{config} in our example) allows us to run tests only from this specific
group.

The last thing we need to discuss in this example is \c{$~}. This variable
stands for the scope working directory (we will talk more about working
directories at the end of this introduction).

Besides explicit group scopes, each test is automatically placed in its own
implicit test scope. However, we can make the test scope explicit, for
example, for better visual separation of complex tests:

\
: config-greet
{
  conf = hello.conf

  cat <'Jane = Good day' >=$conf
  $* -c $conf 'Jane' >'Good day, Jane!'
}
\

A test scope is a \c{{}-style scope that contains one or more commands. Notice
that in this case we don't use the semicolon (\c{;}) to indicate that multiple
commands belong to the same test.

We can conditionally exclude sections of a testscript using the \c{if-else}
branching. This can be done both at the scope level to exclude test or group
scopes as well as at the command level to exclude individual commands or
variable assignments. Let's start with a scope example by providing a
Windows-specific implementation of a test:

\
: config-empty
:
if ($cxx.target.class != windows)
{
  $* -c /dev/null 'Jane' >'Hello, Jane!'
}
else
{
  $* -c nul 'Jane' >'Hello, Jane!'
}
\

Note that the scopes in the \c{if-else} chain are treated as variants of the
same test or group thus the single description at the beginning. An example
of a conditional group:

\
: config-empty
:
if ($cxx.target.class != windows)
{{
  $* -c /dev/null 'John' >'Hello, John!' : john
  $* -c /dev/null 'Jack' >'Hello, Jack!' : jack
}}
else
{{
  $* -c nul 'John' >'Hello, John!' : john
  $* -c nul 'Jack' >'Hello, Jack!' : jack
}}
\

Let's now see an example of command-level \c{if-else} by reimplementing
the above as a single test with some branching and without using the
\c{nul} device on Windows (notice the semicolon after \c{\}}):

\
: config-empty
:
if ($cxx.target.class != windows)
{
  conf = /dev/null
}
else
{
  conf = empty
  touch $conf
};
$* -c $conf 'Jane' >'Hello, Jane!'
\

You may have noticed that in the above examples we referenced the
\c{cxx.target.class} variable as if we were in a buildfile. We could do that
because the testscript variable lookup continues in the buildfile starting
from the target being tested, then the testscript target, and continuing with
the standard scope lookup (see \l{#model Model and Execution} for details). In
particular, this means we can pass arbitrary information to testscripts using
target-specific variables. For example, this is how we can move the above
platform test to \c{buildfile}:

\
# buildfile

exe{hello}: cxx{hello} testscript

testscript{*}: windows = ($cxx.target.class == windows)
\

\
# testscript

if! $windows
  conf = /dev/null
else
  ...
\

Note also that in cases where you simply need to conditionally pick a value
for a variable, the \c{build2} evaluation context will often be a more concise
option. For example:

\
: config-empty
:
conf = ($windows ? nul : /dev/null);
$* -c $conf 'Jane' >'Hello, Jane!'
\

Similar to Bash, test commands can be chained with pipes (\c{|}) and combined
with logical operators (\c{||} and \c{&&}). Let's say our \c{hello} program
provided the \c{-o} option to write the result to a file instead of
\c{stdout}. Here is how we could test it:

\
$* -o hello.out - <<EOI &hello.out && cat hello.out >>EOO
John
Jane
EOI
Hello, John!
Hello, Jane!
EOO
\

Similarly, if it had the \c{-r} option to reverse the greetings back to
their names (as every \c{hello} program should), then we could write a
test like this:

\
$* - <<EOI | $* -r - >>EOO
John
Jane
EOI
John
Jane
EOO
\

To conclude, let's put all our (sensible) tests together so that we can have a
complete picture:

\
$* 'World' >'Hello, World!' : command-name

$* 'John' 'Jane' >>EOO      : command-names
Hello, Jane!
Hello, John!
EOO

$* - <<EOI >>EOO            : stdin-names
Jane
John
EOI
Hello, Jane!
Hello, John!
EOO

: config
{{
  conf = $~/hello.conf

  +cat <<EOI >=$conf
  John = Howdy
  Jane = Good day
  EOI

  $* -c $conf 'John' >'Howdy, John!' : custom-greet
  $* -c $conf 'Jack' >'Hello, Jack!' : default-greet
}}

$* 2>>\"EOE\" != 0            : missing-name
error: missing name
usage: $0 <name>
EOE
\

Testscript isolates tests from each other by running each test in its own
temporary working directory under \c{out_base}. For the above \c{testscript}
the working directory structure will be as follows:

\
$out_base/
└── test-hello/
    ├── command-name/
    ├── command-names/
    ├── stdin-names/
    ├── config/
    │   ├── hello.conf
    │   ├── custom-greet/
    │   └── default-greet/
    └── missing-name/
\

If all the tests succeed, then this working directory structure is
automatically removed. In case of a failure, however, it is left behind in
case you need to examine the output of the failed tests. It will be
automatically cleaned on the subsequent run, before executing any tests.

The execution of tests happens in parallel. In the above case Testscript can
start running all the top-level tests as well as the \c{config} group
immediately.  Inside \c{config}, once the setup command (\c{cat}) is
completed, the two inner tests are executed in parallel as well. Refer to
\l{#model Model and Execution} for details on the working directory structure
and test execution.


\h1#integration|Build System Integration|

The integration of testscripts into buildfiles is done using the standard
\c{build2} \i{target-prerequisite} mechanism. In this sense, a testscript is a
prerequisite that describes how to test the target similar to how, for
example, the \c{INSTALL} file describes how to install it. For example:

\
exe{hello}: testscript doc{INSTALL README}
\

By convention, the testscript file should be called either \c{testscript} if
you only have one or have the \c{.testscript} extension, for example,
\c{basics.testscript}. The \c{test} module registers the \c{testscript{\}}
target type to be used for testscript files. We don't have to use explicit
target type for the \c{testscript} file. For example:

\
exe{hello}: testscript{basics advanced}
\

A testscript prerequisite can be specified for any target. For example, if
our directory contains a bunch of executables that we want to test together,
then it makes sense to specify the testscript prerequisite for the directory
target:

\
./: testscript
\

Similarly, the same testscript can be used to test multiple targets. For
example:

\
exe{hello}:      testscript{basics advanced}
exe{hello-lite}: testscript{basics}
\

During variable lookup if a variable is not found in one of the testscript
scopes (see \l{#model Model and Execution}), then the search continues in the
\c{buildfile} starting with the target-specific variables of the target being
tested (e.g., \c{exe{hello\}}; called \i{test target}), then target-specific
variables of the testscript target (e.g., \c{testscript{basics\}}; called
\i{script target}), and then continuing with the scopes starting with the one
containing the script target. As a result, a testscript can \"see\" all the
existing buildfile variables plus we can use target-specific variables to pass
additional, test-specific, information to testscrips. As an example, consider
this testscript and buildfile pair:

\
# basics.testscript

if ($cxx.target.class == windows)
  test.arguments += $foo

if $windows
  test.arguments += $bar
\

\
# buildfile

exe{hello}: testscript{basics}

# All testscripts in this scope.
#
testscript{*}: windows = ($cxx.target.class == windows)

# All testscripts for target exe{hello}.
#
exe{hello}: bar = BAR

# Only basics.testscript.
#
testscript{basics}@./: foo = FOO
\

Additionally, by convention, a number of pre-defined \c{test.*} variables are
used to pass commonly required information to testscripts, as described next.

Unless set manually as a test or script target-specific variable, the \c{test}
variable is automatically set to the target path being tested. For example,
given this \c{buildfile}:

\
exe{hello}: testscript
\

The value of \c{test} inside the testscript will be the absolute path to the
\c{hello} executable.

If the \c{test} variable is set manually to a name of a target, then it is
automatically converted to the target path. This can be useful when testing a
program that is built in another subdirectory of a project (or even in another
project, via import). For example, our \c{hello} may reside in the \c{hello/}
subdirectory while we may want to keep the tests in \c{tests/}:

\
hello/
├── hello/
│   └── hello*
└── tests/
    ├── buildfile
    └── testscript
\

This is how we can implement \c{tests/buildfile} for this setup:

\
hello = ../hello/exe{hello}

./: $hello testscript
./: test = $hello

include ../hello/
\

The rest of the special \c{test.*} variables are \c{test.options},
\c{test.arguments}, \c{test.redirects}, and \c{test.cleanups}. You can use
them to pass additional command line options, arguments, redirects, and
cleanups to your test scripts. Together with \c{test} these variables form the
\i{test target command} line which, for conciseness, is bound to the following
aliases:

\
$* - $test $test.options $test.arguments $test.redirects $test.cleanups
$0 - $test
$N - (N-1)-th element in the {$test.options $test.arguments} array
\

Note that these aliases are read-only; if you need to modify any of these
values from within testscripts, then you should use the original variable
names, for example:

\
test.options += --foo

$* bar # Includes --foo.
\

Note also that these \c{test.*} variables only establish a convention. You
could also put everything into, say \c{test.arguments}, and it will still work
as expected.

\N|The \c{test.redirects}, \c{test.cleanups}, and \c{$*} variables are of the
special \c{cmdline} type, see \l{#lexical Lexical Structure} for details.|

The special \c{test.*} variables make it fairly easy to arrange the testing of
a single executable. What if we need to run multiple executables from a single
testscript file? For example, we may have a pair of executables, such as
\c{reader} and \c{writer}, that must be tested together. Or we may have a
number of test executables that all require a common setup, for example,
cryptographic key generation, which we would like not to repeating for each
test. While it is possible to achieve this with target-specific variables
similar to \c{test}, things will be less automatic. In particular, there
will be no automatic translation of target names to paths and we will have
to do it manually. For example:

\
# buildfile

./: exe{reader}: cxx{reader} ...
./: exe{writer}: cxx{writer} ...

./: testscript
{
  reader = exe{reader}
  writer = exe{writer}
}
\

\
# testscript

# Translate targets to paths.
#
reader = $path($reader)
writer = $path($writer)

: pipe
:
$writer | $reader

: file
:
$writer output;
$reader output
\

\N|Strictly speaking, for local executables, there is no need to pass the
target names from \c{buildfile} to \c{testscript} and instead we could just
list them literally in \c{testscript}. In particular, this could be an
attractive approach if we have a large number of such executables. For
example:

\
# testscript

$path(exe{test1}) : test1
$path(exe{test2}) : test2
$path(exe{test3}) : test3
...
\

|

Another pre-defined variable is \c{test.target}. It is used to specify the
test target platform when cross-testing (for example, when running Windows
test on Linux under Wine). Normally, you would set it in your
\c{build/root.build} to the cross-compilation target of your toolchain, for
example:

\
# root.build
#

using cxx                 # Load the C++ module (sets sets cxx.target).
test.target = $cxx.target # Set test target to the C++ compiler target.
\

If this variable is not set explicitly, then it defaults to \c{build.host}
(which is the platform on which the build system is running) and only native
testing will be supported.

All the testscripts for a particular test target are executed in a
subdirectory of \c{out_base} (or, more precisely, in subdirectories of this
subdirectory; see \l{#model Model and Execution}). If the test target is a
directory, then the subdirectory is called \c{test}. Otherwise, it is the name
of the target prefixed with\c{test-}. For example:

\
./:         testscript{foo}  # $out_base/test/
exe{hello}: testscript{bar}  # $out_base/test-hello/
\


\h1#model|Model and Execution|

A testscript file is a set of nested scopes. A scope is either a group scope
or a test scope. Group scopes can contain nested group and test scopes. Test
scopes can only contain test commands.

Group scopes are used to organize related tests with shared variables as well
as setup and teardown commands. Explicit test scopes are normally used for
better visual separation of complex tests.

The top level scope is always an implicit group scope corresponding to the
entire script file. If there is no explicit scope for a test, one is
established implicitly. As a result, a testscript file always starts with a
group scope which then contains other group scopes and/or test scopes,
recursively.

A scope (both group and test) has an \i{id}. If not specified explicitly (as
part of the description), it is derived automatically from the group/test
location in the testscript file (see \l{#syntax-description Description} for
details). The id of the implicit outermost scope is the script file name
without the \c{.testscript} extension, except if the file name is
\c{testscript}, in which case the id is empty.

Based on the ids each nested group and test has an \i{id path} that uniquely
identifies it. It starts with the id of the implied outermost group (unless
empty), may include a number of intermediate group ids, and ends with the
final test or group id. The ids in the path are separated with a forward slash
(\c{/}). Note that this also happens to be the relative filesystem path to the
temporary directory where the test is executed (as described below). Inside a
scope its id path is available via the special \c{$@} variable (read-only).

As an example, consider the following testscript file which we assume is
called \c{basics.testscript}:

\
test0: test0

: group
{{
  test1

  : test2
  {
    test2a
    test2b
  }
}}
\

Below is its version annotated with the id paths that also shows all the
implicit scopes:

\
# basics
{{
  # basics/test0
  {
    test0
  }

  # basics/group
  {{
    # basics/group/5
    {
      test1
    }

    # basics/group/test2
    {
      test2a
      test2b
    }
  }}
}}
\

A scope establishes a nested variable context. A variable set within a scope
will only have effect until the end of this scope. Variable lookup is
performed starting from the scope where the variable is referenced (expanded),
continuing with the outer testscript scopes, and then continuing in the
buildfile as described in \l{#integration Build System Integration}.

A scope also establishes a cleanup context. All cleanups (\l{#syntax-cleanup
Cleanup}) registered in a scope are performed at the end of that scope's
execution in the reverse order of their registration.

Prior to executing a scope, a nested temporary directory is created with the
scope id as its name. This directory then becomes the scope's working
directory. After executing the scope (and after performing cleanups) this
temporary directory is automatically removed provided that it is empty. If it
is not empty, then the test is considered to have failed (unexpected output).
Inside a scope its working directory is available via the special \c{$~}
variable (read-only).

As an example, consider the following version of \c{basics.testscript}. We
also assume that its test target is a directory (so the target test directory
is \c{$out_base/test/}).

\
: group
{{
  foo = FOO
  bar = BAR

  +setup &out-setup

  : test1
  {
    bar = BAZ
    test1 $foo $bar
  }

  test2 $bar: test2
}}

test3 $foo &out-test
\

Below is its annotated version:

\
{{                         # $~ = $out_base/test/basics/
  {{                       # $~ = .../test/basics/group/
    foo = FOO
    bar = BAR

    +setup &out-setup

    {                      # $~ = .../basics/group/test1/
      bar = BAZ
      test1 $foo $bar      # test1 FOO BAZ
    }

    {                      # $~ = .../basics/group/test2/
      test2 $bar           # test2 BAR
    }
  }}                       # Remove out-setup.

  {                        # $~ = .../test/basics/17/
    test3 $foo &out-test   # test3
  }                        # Remove out-test.
}}
\

A test should normally create files or directories, if any, in its working
directory to ensure test isolation. A test can, however, access (but normally
should not modify) files created by an outer group's setup commands. Because
of this nested directory structure this can be done using \c{../}-based
relative paths, for example:

\
{{
  +setup >=test.conf

  test1 ../test.conf
  test2 ../test.conf
}}
\

Alternatively, we can use an absolute path:

\
{{
  conf = $~/test.conf
  +setup >=$conf

  test1 $conf
  test2 $conf
}}
\

Inside the scope working directory filesystem names that start with \c{stdin},
\c{stdout}, and \c{stderr} are reserved.

To execute a test scope its commands (including variable assignments) are
executed sequentially and in the order specified. If any of the commands
fails, no further commands are executed and the test is considered to have
failed.

Executing a group scope starts with performing its setup commands (including
variable assignments) sequentially and in the order specified. If any of them
fail, the group execution is terminated and the group is considered to have
failed.

After completing the setup, inner scopes (both group and test) are
executed. Because scopes are isolated and tests are assumed not to depend on
each other, the execution of inner scopes can be performed in parallel.

After completing the execution of the inner scopes, if all of them succeeded,
the teardown commands are executed sequentially and in the order specified.
Again, if any of them fail, the group execution is terminated and the group is
considered to have failed.

\N|Currently, the only way to run several executables serially is to place
them into a single compound test. See \l{#syntax-test Test} for details.|

As an example, consider the following version of \c{basics.testscript}:

\
test0

: group
{{
  +setup1
  +setup2

  test1
  test2
  test3

  -teardown2
  -teardown1
}}
\

At the top level, both \c{test0} and \c{group} can start executing in
parallel. Inside \c{group}, first the two setup commands are executed
sequentially. Once the setup is completed, \c{test1}, \c{test2}, \c{test3}
can all be executed in parallel (along with \c{test0} which may still be
running). Once the three inner tests complete successfully, the \c{group}'s
teardown commands are executed sequentially. At the top level, the script
is completed only when both \c{test0} and \c{group} complete.

The following annotated version illustrates a possible thread scheduling
for this example:

\
{{              # thread 1

  test0         # thread 2

  : group       # thread 1
  {{
    +setup1     # thread 1
    +setup2     # thread 1

    test1       # thread 3
    test2       # thread 4
    test3       # thread 1

                # thread 1 (wait for 3 & 4)

    -teardown2  # thread 1
    -teardown1  # thread 1
  }}
                # thread 1 (wait for 2)
}}
\

A testscript would normally contain multiple tests and sometimes it is
desirable to only execute a specific test or a group of tests. For example,
you may be debugging a failing test and would like to re-run it. As an
example, consider the following testscript file called \c{basics.testscript}:

\
$* foo : foo

: fox
{{
  $* fox bar : bar
  $* fox baz : baz
}}
\

The id paths for these three test will then be:

\
basics/foo
basics/fox/bar
basics/fox/baz
\

To only run individual tests, test groups, or testscript files we can specify
their id paths in the \c{config.test} variable, for example:

\
$ b test config.test=basics                   # All in basics.testscript
$ b test config.test=basics/fox               # All in fox
$ b test config.test=basics/foo               # Only foo
$ b test config.test=\"basics/foo basics/fox/bar\" # Only foo and bar
\

The test commands (\c{$0}, \c{$*}) can be executed via a \i{runner program} by
specifying the \c{config.test.runner} variable (see \l{build2#module-test
\c{test}} module for details). For example:

\
$ b test config.test.runner=\"valgrind -q\"
\

The script working directory may exist before the execution (for example,
because of a failed previous run) or it may be desirable not to clean it up
after the execution (for example, to examine test setup, output, etc). Before
the execution the default behavior is to warn and then automatically remove
the working directory if it exists. After the execution the default behavior
is to perform all the cleanups and teardowns and then remove the working
directory if it is not empty. This default behavior can, however, be
overridden with the \c{config.test.output} variable.

The \c{config.test.output} variable contains a pair of values with the first
signifying the \i{before} behavior and the second \- \i{after}. The valid
\i{before} values are \c{fail} (fail if the directory exists), \c{warn} (warn
if the directory exists then remove), \c{clean} (silently remove the existing
directory). The valid \i{after} values are \c{clean} (remove the directory if
it is not empty) and \c{keep} (do not run cleanups and teardowns and do not
remove the working directory). The default behavior is thus equivalent to
specifying the \c{warn@clean} pair.

If only a single value is specified in \c{config.test.output} then it is
assumed to be the \i{after} value and the \i{before} value is assumed to
be \c{clean}. In other words:

\
$ b test config.test.output=clean # config.test.output=clean@clean
$ b test config.test.output=keep  # config.test.output=clean@keep
\

Note also that selecting the \c{keep} behavior may result in some test
failures (due to unexpected output) to go undetected.

\h1#lexical|Lexical Structure|

At the lexical level, testscripts are UTF-8 encoded text restricted to the
Unicode graphic characters, tabs (\c{\\t}), carriage returns (\c{\\r}), and
line feeds (\c{\\n}).

Testscript is a line-oriented language with a context-dependent lexical
structure. It \"borrows\" several building blocks (variable expansion,
function calls, and evaluation contexts; collectively called \i{expansions}
from now on) from the Buildfile language. In a sense, testscripts are
specialized (for testing) continuations of buildfiles.

Except in here-document fragments, leading whitespaces and blank lines are
ignored except for the line/column counting. A non-empty testscript must
end with a newline.

Except in single-quoted strings and single-quoted here-document fragments,
the backslash (\c{\\}) character followed by a newline signals the line
continuation. Both this character and the newline are removed (note: not
replaced with a whitespace) and the following line is read as if it was part
of the first line. Note that \c{'\\'} followed by EOF is invalid. For example:

\
$* foo | \
$* bar
\

Except in quoted strings and here-document fragments, an unquoted and
unescaped \c{'#'} character starts a comment; everything from this character
until the end of the line is ignored. For example:

\
# Setup foo.
$* foo

$* bar # Setup bar.
\

There is no line continuation support in comments; the trailing \c{'\\'} is
ignored except in one case: if the comment is just \c{'#\\'} followed by the
newline, then it starts a multi-line comment that spans until the closing
\c{'#\\'} is encountered. For example:

\
#\
$* foo
$* bar
#\

$* foo #\
$* bar
$* baz #\
\

Similar to Buildfile, the Testscript language supports two types of quoting:
single (\c{'}) and double (\c{\"}). Both can span multiple lines.

The single-quoted strings and single-quoted here-document fragments do not
recognize any expansions or escape sequences (not even for the single quote
itself or line continuations) with all the characters taken literally until
the closing single quote or here-document end marker is encountered.

The double-quoted strings and double-quoted here-document fragments recognize
expansions and escape sequences (including line continuations). For example:

\
foo = FOO

# 'FOO true'
#
bar = \"$foo ($foo == FOO)\"

# 'FOO bool'
#
$* <<\"EOI\"
$foo $type($foo == FOO)
EOI
\

Characters that have special syntactic meaning (for example \c{'$'}) can be
escaped with a backslash (\c{\\}) to preserve their literal meaning (to
specify literal backslash you need to escape it as well). For example:

\
foo = \$foo\\\\bar # '$foo\bar'
\

Note that quoting could often be a more readable way to achieve the same
result, for example:

\
foo = '$foo\bar'
\

Inside double-quoted strings only the \c{\"\\$(} character set needs to be
escaped. Inside double-quoted here-document fragments \- only \c{\\$(} (since
in here-documents quotes are taken literally).

The lexical structure of a line depends on its type. The line type could be
dictated by the preceding construct, as is the case for here-document
fragments. Otherwise, the line type is determined by examining the leading
character and, if that fails to determine the line type, leading tokens, as
described next.

A character is said to be \i{unquoted} and \i{unescaped} if it is not escaped
and is not part of a quoted string. A token is said to be unquoted and
unescaped if all its characters are unquoted and unescaped.

The following characters determine the line type if they appear unquoted and
unescaped at the beginning of the line:

\
':'  - description line
'.'  - directive line
'{'  - scope/block start
'}'  - scope/block end
'+'  - setup command line
'-'  - teardown command line
\

\N|If the leading \c{'{'}/\c{'\}'} characters are followed by the second
\c{'{'}/\c{'\}'} (respectively), then they start/end a group scope. Otherwise,
they start/end a test scope or command block, depending on the context (see
the grammar below for details).|

If the line doesn't start with any of these characters then the first token of
the line is examined in the \c{first_token} mode (see below). If the first
token is an unquoted word, then the second token of the line is examined in
the \c{second_token} mode (see below). If it is a variable assignment (either
\c{+=}, \c{=+}, or \c{=}), then the line type is a variable line. Otherwise,
it is a test command line. Note that variables with computed names can only
be set using the \l{#builtins-set \c{set}} pseudo-builtin.

The Testscript language defines the following distinct lexing modes (or
contexts):

\dl|

\li|\n\n\cb{command_line}\n

  Whitespaces are token separators. The following characters and character
  sequences (read vertically, for example, \c{==}, \c{!=} below) are
  recognized as tokens:

  \
  :;=!|&<>$(#
    ==
  \

  |

\li|\n\n\cb{first_token}\n

  Like \c{command_line} but recognizes variable assignments as separators.|

\li|\n\n\cb{second_token}\n

  Like \c{command_line} but recognizes variable assignments as tokens.|

\li|\n\n\cb{command_expansion}\n

  Subset of \c{command_line} used for re-lexing expansions (described
  below). Only the \c{|&<>} characters are recognized as tokens. Note that
  whitespaces are not separators in this mode.|

\li|\n\n\cb{variable_line}\n

  Similar to the Buildfile \cb{value} mode. The \c{;$([]} characters are
  recognized as tokens.|

\li|\n\n\cb{description_line}\n

  Like a single-quoted string.|

\li|\n\n\cb{here_line_single}\n

  Like a single-quoted string except it treats newlines as separators and
  quotes as literals.|

\li|\n\n\cb{here_line_double}\n

  Like a double-quoted string except it treats newlines as separators and
  quotes as literals. The \c{$(} characters are recognized as tokens.||

Besides having a varying lexical structure, parsing some line types involves
performing expansions (variable expansions, function calls, and evaluation
contexts). The following table summarizes the mapping of line types to lexing
modes and indicates whether they are parsed with expansions:

\
variable line                 variable_line      expansions
directive line                command_line       expansions
description line              description_line

test command line             command_line       expansions
setup command line            command_line       expansions
teardown command line         command_line       expansions

here-document single-quoted   here_line_single
here-document double-quoted   here_line_double   expansions
\

Finally, unquoted expansions in command lines (test, setup, and teardown) of
the special \c{cmdline} type are re-lexed in the \c{command_expansion} mode in
order to recognize command line syntax tokens (redirects, pipes, etc). To
illustrate this mechanism, consider the following example of a \"canned\"
command line:

\
cmd = [cmdline] echo >-
$cmd foo
\

The test command line token sequence will be \c{$}, \c{cmd}, \c{foo}. After
the expansion we have \c{echo}, \c{>-}, \c{foo}, however, the second element
(\c{>-}) is not (yet) recognized as a redirect. To recognize it, the result of
the expansion is re-lexed.

Note that besides the few command line syntax characters, re-lexing will also
\"consume\" quotes and escapes, for example:

\
cmd = [cmdline] echo \"'foo'\"  # echo 'foo'
$cmd                          # echo foo
\

To preserve quotes in this context we need to escape them:

\
cmd = [cmdline] echo \"\\\\'foo\\\\'\"  # echo \'foo\'
$cmd                              # echo 'foo'
\

To minimize unhelpful consumption of escape sequences (for example, in Windows
paths), re-lexing only performs the \i{effective escaping} for the \c{'\"\\}
characters. All other escape sequences are passed through uninterpreted. Note
that this means there is no way to escape command line syntax characters in
canned commands. The recommendation is to use quoting except for passing
literal quotes, for example:

\
cmd = [cmdline] echo \'&foo\'  # echo '&foo'
$cmd                           # echo &foo
\

To make sure that a string is passed as is through both expansions use the
\i{doubled single-quoting} idiom, for example:

\
filter = [cmdline] sed -e \''s/foo (bar|baz)/$&/'\'
$* <<EOI | $filter >>EOO
...
EOI
...
EOO
\

\h1#syntax|Syntax and Semantics|

\h#syntax-notation|Notation|

The formal grammar of the Testscript language is specified using an EBNF-like
notation with the following elements:

\
foo: ...   - production rule
foo        - non-terminal
<foo>      - terminal
'foo'      - literal
foo*       - zero or more multiplier
foo+       - one or more multiplier
foo?       - zero or one multiplier
foo bar    - concatenation (foo then bar)
foo | bar  - alternation   (foo or bar)
(foo bar)  - grouping
{foo bar}  - grouping in any order (foo then bar or bar then foo)
foo\
bar        - line continuation
# foo      - comment
\

A rule's right-hand-sides that start on a new line describe the line-level
syntax and ones that start on the same line describes the syntax inside the
line. If a rule contains multiple lines, then each line matches a separate
line in the input.

If a multiplier appears in front of a line then it specifies the number of
repetitions of the entire line. For example, from the following three rules,
the first describes a single line of multiple literals, the second \- multiple
lines of a single literal, and the third \- multiple lines of multiple
literals.

\
# foofoofoo
#
text-line: 'foo'+

# foo
# foo
# foo
#
text-lines:
  +'foo'

# foo
# foofoo
# foofoofoo
#
text-lines:
  +('foo'+)
\

A newline in the grammar matches any standard newline separator sequence
(CR/LF combinations). An unquoted space in the grammar matches zero or more
non-newline whitespaces (spaces and tabs). A quoted space matches exactly one
non-newline whitespace. Note also that in some cases components within lines
may not be whitespace-separated in which case they will be written without any
spaces between them, for example:

\
foo: 'foo' ';'    # 'foo;' or 'foo ;' or 'foo      ;'
bar: 'bar'';'     # 'bar;'
baz: 'baz'' '+';' # 'baz ;' or 'baz      ;'

fox: bar''bar     # 'bar;bar;'
\

You may also notice that several production rules below end with \c{-line}
while potentially spanning several physical lines. The \c{-line} suffix
here signifies a \i{logical line}, for example, a command line plus its
here-document fragments.


\h#syntax-grammar|Grammar|

The complete grammar of the Testscript language is presented next with the
following sections discussing the semantics of each production rule.

\
script:
  group-body

group-body:
  *setup
  *(group|test|directive)
  *tdown

group:
  group-scope|group-if

group-scope:
  ?description
  group-block

group-block:
  '{{'
  group-body
  '}}'

description:
  +(':' <text>)

group-if:
  ?description
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  group-block
  *group-elif
  ?group-else

group-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  group-block

group-else:
  'else'
  group-block

setup:
  variable-like|setup-line

tdown:
  variable-like|tdown-line

setup-line: '+' command-like
tdown-line: '-' command-like

test:
  test-commands|test-scope|test-if

test-commands:
  test-commands-leading-description | \
  test-commands-trailing-description

test-commands-leading-description:
  ?description
  *(test-command ';')
    test-command

test-commands-trailing-description:
  *(test-command ';')
    test-command ':' <text>

test-command:
  variable-line|command-like

test-scope:
  ?description
  test-block

test-block:
  '{'
  *(test-command|directive)
  '}'

test-if:
  ?description
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  test-block|test-command
  *test-elif
  ?test-else

test-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  test-block|test-command

test-else:
  'else'
  test-block|test-command

directive:
  '.' include

include: 'include' (' '+'--once')*(' '+<path>)*

variable-like:
  variable-line|variable-flow

variable-line:
  <variable-name> ('='|'+='|'=+') value-line

value-line: value-attributes? <value>

value-attributes: '[' <key-value-pairs> ']'

variable-flow:
  variable-if|variable-for|variable-while|variable-loop-flow

variable-if:
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  variable-block|variable-like
  *variable-elif
  ?variable-else

variable-block:
  '{'
  *(variable-like|directive)
  '}'

variable-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  variable-block|variable-like

variable-else:
  'else'
  variable-block|variable-like

variable-for:
  variable-for-value|variable-for-stream

variable-for-value:
  'for' <variable-name> element-attributes? ':' value-line
  variable-block|variable-like

element-attributes: value-attributes

variable-for-stream:
  (command-pipe '|')? \
  'for' (<opt>|stdin)* <variable-name> element-attributes? (stdin)*
  variable-block|variable-like

variable-while:
  'while' command-line
  variable-block|variable-like

variable-loop-flow: 'continue'|'break'

command-like:
  command-line|command-flow

command-line:
  command-expr
  *here-document

command-expr: command-pipe (('||'|'&&') command-pipe)*

command-pipe: command ('|' command)*

command: <path>(' '+(<arg>|redirect|cleanup))* command-exit?

command-exit: ('=='|'!=') <exit-status>

command-flow:
  command-if|command-for|command-while|command-loop-flow

command-if:
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  command-block|command-or-variable
  *command-elif
  ?command-else

command-block:
  '{'
  *(command-or-variable|directive)
  '}'

command-or-variable:
  variable-line|command-like

command-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  command-block|command-or-variable

command-else:
  'else'
  command-block|command-or-variable

command-for:
  command-for-value|command-for-stream

command-for-value:
  'for' <variable-name> element-attributes? ':' value-line
  command-block|command-or-variable

command-for-stream:
  (command-pipe '|')? \
  'for' (<opt>|stdin)* <variable-name> element-attributes? (stdin)*
  command-block|command-or-variable

command-while:
  'while' command-line
  command-block|command-or-variable

command-loop-flow: 'continue'|'break'

redirect: stdin|stdout|stderr

stdin:  '0'?(in-redirect)
stdout: '1'?(out-redirect)
stderr: '2'(out-redirect)

in-redirect:  '<-'|\
              '<|'|\
              ('<<<'|'<=') <file>|\
              ('<<'|'<<='){':'?'/'?} <here-end>|\
              ('<'|'<<<='){':'?'/'?} <text>

out-redirect: '>-'|\
              '>|'|\
              '>!'|\
              '>=' <file>|\
              '>+' <file>|\
              '>&' ('1'|'2')|\
              ('>>>'|'>?') <file>|\
              ('>>'|'>>?'){':'?'/'?}'~'? <here-end>|\
              ('>'|'>>>?'){':'?'/'?}'~'? <text>

here-document:
  *<text>
  <here-end>

cleanup: ('&'|'&?'|'&!') (<file>|<dir>)
\

Note that the only purpose of having separate (from the command flow control
constructs) variable-only flow control constructs is to remove the error-prone
requirement of having to specify \c{+} and \c{-} prefixes in group
setup/teardown.


\h#syntax-if|Group/Test/Variable/Command-If|

The \c{if} and \c{elif} branches of the \c{*-if} flow control constructs are
taken if their condition \c{command-line} terminates normally with the zero
code. The \c{if!} and \c{elif!} branches, on the contrary, are taken if their
\c{command-line} terminates normally with a non-zero code. If the
\c{command-line} terminates abnormally, then the flow control construct is
considered to have failed.

Besides these general \c{if}-constructs there is also a number of specialized
shortcuts for checking whether a value is/is-not \c{null} or empty:

\
ifn ...     ~  if $null(...)
ife ...     ~  if $empty(...)

ifn! ...    ~  if! $null(...)
ife! ...    ~  if! $empty(...)

elifn ...   ~  elif $null(...)
elife ...   ~  elif $empty(...)

elifn! ...  ~  elif! $null(...)
elife! ...  ~  elif! $empty(...)
\

For example, the following two script fragments are equivalent:

\
if $null($foo)
  ...
elif! $empty($bar)
  ...
\

\
ifn $foo
  ...
elife! $bar
  ...
\

Note that unlike the general \c{if}-constructs, conditions for these shortcuts
are values rather than commands. Note also that a \c{null} value is considered
empty.


\h#syntax-script|Script|

\
script:
  group-body
\

A testscript file is an implicit group scope (see \l{#model Model and
Execution} for details).


\h#syntax-group|Group|

\
group-body:
  *setup
  *(group|test|directive)
  *tdown

group:
  group-scope|group-if

group-scope:
  ?description
  group-block

group-block:
  '{{'
  group-body
  '}}'
\

A group is an \c{{{}-style scope that contains nested group and test scopes as
well as directives (see \l{#model Model and Execution} for details).


\h#syntax-description|Description|

\
description:
  +(':' <text>)
\

Description lines start with a colon (\c{:}) and are used to document tests
and test groups. In a sense they are formalized comments.

A description can be \i{leading}, that is, specified before the test or
group. For implicit test scopes it can also be \i{trailing} \- specified as a
single line after the (last) command of the test. It is an error to specify
both leading and trailing descriptions.

By convention the leading description has the following format with all three
components being optional.

\
: <id>
: <summary>
:
: <details>
\

If the first line in the description does not contain any whitespaces, then it
is assumed to be the test or test group id. If the next line is followed by a
blank line, then it is assumed to be the test or test group summary. After the
blank line come optional details which are free-form.

The trailing description can only be used to specify the id or summary (but
not both).

If an id is not specified then it is automatically derived from the test or
test group location. If the test or test group is contained directly in the
top-level testscript file, then just its start line number is used as an id.
Otherwise, if the test or test group resides in an included file, then the
start line number (inside the included file) is prefixed with the line number
of the \c{include} directive followed by the included file name (without the
extension) in the form \c{<line>-<file>-}. This process is repeated
recursively in case of nested inclusions.

The start line for an explicit scope (either test or group) is the line
containing its opening brace (\c{{} or \c{{{}) and for an implicit test scope
\- the first test line.


\h#syntax-group-if|Group-If|

\
group-if:
  ?description
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  group-block
  *group-elif
  ?group-else

group-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  group-block

group-else:
  'else'
  group-block
\

A group scope can be executed conditionally. The condition \c{command-line} is
executed in the context of the outer scope. Similarly, the condition
\c{value-line} is expanded in the context of the outer scope. See
\l{#syntax-if Group/Test/Variable/Command If} for details on the semantics.

Note that all the scopes in an \c{if-else} chain are alternative
implementations of the same group (thus the single description).


\h#syntax-setup-teardown|Setup and Teardown|

\
setup:
  variable-like|setup-line

tdown:
  variable-like|tdown-line

setup-line: '+' command-like
tdown-line: '-' command-like
\

Note that variable assignments (including \c{variable-flow}) do not use the
\c{'+'} and \c{'-'} prefixes. A standalone (not part of a test) variable
assignment is automatically treated as a setup if no tests have yet been
encountered in this scope and as a teardown otherwise.


\h#syntax-test|Test|

\
test:
  test-commands|test-scope|test-if

test-commands:
  test-commands-leading-description | \
  test-commands-trailing-description

test-commands-leading-description:
  ?description
  *(test-command ';')
    test-command

test-commands-trailing-description:
  *(test-command ';')
    test-command ':' <text>

test-command:
  variable-line|command-like

test-scope:
  ?description
  test-block

test-block:
  '{'
  *(test-command|directive)
  '}'
\

A test is a sequence of one or more command lines and, optionally, one or more
variable assignment lines. Test lines enclosed in \c{{\}} establish an
explicit test scope. Otherwise, a test scope is established implicitly.
Explicit test scopes may contain directives, besides commands and variable
assignments.

A test that contains multiple lines is called \i{compound}. In a compound test
with implicit test scope each (logical) line except the last must end with a
semicolon to signal the test continuation. For example:

\
conf = test.conf;
cat <'verbose = true' >=$conf;
test1 $conf
\

\N|As discussed in \l{#model Model and Execution}, tests are executed in
parallel. Currently, the only way to run several executables serially is to
place them into a single compound test.|


\h#syntax-test-if|Test-If|

\
test-if:
  ?description
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  test-block|test-command
  *test-elif
  ?test-else

test-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  test-block|test-command

test-else:
  'else'
  test-block|test-command
\

A test scope can be executed conditionally. The condition \c{command-line} is
executed in the context of the outer scope. Similarly, the condition
\c{value-line} is expanded in the context of the outer scope. See
\l{#syntax-if Group/Test/Variable/Command If} for details on the semantics.

Note that all the scopes in an \c{if-else} chain are alternative
implementations of the same test (thus the single description).


\h#syntax-directive|Directive|

\
directive:
  '.' include
\

A line that starts with \c{.} is a Testscript directive. Note that directives
are evaluated during parsing, before any command is executed or (testscript)
variable is assigned. You can, however, use variables assigned in the
buildfile. For example:

\
.include common-$(cxx.target.class).testscript
\

\h2#syntax-directive-include|Include|

\
include: 'include' (' '+'--once')*(' '+<path>)*
\

While in the grammar the \c{include} directive is shown to only appear
interleaving with groups and tests, it can be used anywhere in the group
body. It can also contain several parts of a group scope, for example, setup
and test lines.

When used in variable-only flow control constructs it may only contain
variable assignments and variable-only flow control constructs,
recursively.

The \c{--once} option signals that files that have already been included in
this scope should not be included again. The implementation is not required to
handle links when determining if two paths are to the same file. Relative
paths are assumed to be relative to the including testscript file.


\h#syntax-variable|Variable|

\
variable-like:
  variable-line|variable-flow

variable-line:
  <variable-name> ('='|'+='|'=+') value-line

value-line: value-attributes? <value>

value-attributes: '[' <key-value-pairs> ']'

variable-flow:
  variable-if|variable-for|variable-while|variable-loop-flow

variable-loop-flow: 'continue'|'break'
\

The Testscript variable assignment semantics is equivalent to Buildfile except
that no \c{{\}}-based name-generation is performed. For example:

\
args = [strings] foo   bar 'fox   baz'
echo $args # foo bar fox   baz
\

The value can contain variable expansions, function calls, eval contexts, and
literal values. Inside an implicit test scope the value can be followed by a
semicolon to signal the test continuation.

Note that \c{variable-loop-flow} is only valid inside the \c{variable-for} and
\c{variable-while} loop constructs. The \c{continue} line interrupts the
current iteration of the nearest containing loop and starts the next
iteration, subject to the normal \c{for} and \c{while} loop termination
semantics. The \c{break} line interrupts the current iteration and terminates
the loop.


\h#syntax-variable-if|Variable-If|

\
variable-if:
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  variable-block|variable-like
  *variable-elif
  ?variable-else

variable-block:
  '{'
  *(variable-like|directive)
  '}'

variable-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  variable-block|variable-like

variable-else:
  'else'
  variable-block|variable-like
\

A group of variables can be set conditionally. The condition \c{command-line}
and \c{value-line} semantics are the same as in \c{test-if}. For example:

\
if ($cxx.target.class == 'windows')
{
  slash = \\\\
  case = false
}
else
{
  slash = /
  case = true
}
\

When conditionally setting a single variable, using the evaluation context
with a ternary operator is often more concise:

\
slash = ($cxx.target.class == 'windows' ? \\\\ : /)
\


\h#syntax-variable-for|Variable-For|

\
variable-for:
  variable-for-value|variable-for-stream

variable-for-value:
  'for' <variable-name> element-attributes? ':' value-line
  variable-block|variable-like

element-attributes: value-attributes

variable-for-stream:
  (command-pipe '|')? \
  'for' (<opt>|stdin)* <variable-name> element-attributes? (stdin)*
  variable-block|variable-like
\

A group of variables can be set in a loop while iterating over elements of a
list. The iteration semantics is the same as in \c{command-for}. For example:

\
uvalues =
for v: $values
  uvalues += $string.ucase($v)
\

Another example:

\
uvalues =
cat values.txt | for -n v
  uvalues += $string.ucase($v)
\

Or using the \c{stdin} redirect:

\
uvalues =
for -n v <=values.txt
  uvalues += $string.ucase($v)
\


\h#syntax-variable-while|Variable-While|

\
variable-while:
  'while' command-line
  variable-block|variable-like
\

A group of variables can be set in a loop while the condition evaluates to
\c{true}. The condition \c{command-line} semantics is the same as in
\c{variable-if}. For example:

\
uvalues =
i = [uint64] 0
n = $size($values)
while ($i != $n)
{
  uvalues += $string.ucase($values[$i])
  i += 1
}
\


\h#syntax-command|Command|

\
command-like:
  command-line|command-flow

command-line:
  command-expr
  *here-document

command-expr: command-pipe (('||'|'&&') command-pipe)*

command-pipe: command ('|' command)*

command: <path>(' '+(<arg>|redirect|cleanup))* command-exit?

command-exit: ('=='|'!=') <exit-status>

command-flow:
  command-if|command-for|command-while|command-loop-flow

command-loop-flow: 'continue'|'break'
\

A command line is a command expression. If it appears directly (as opposed to
inside \c{command-flow}) in an implicit test scope, then it can be followed by
\c{;} to signal the test continuation or by \c{:} and the trailing
description.

A command expression can combine several command pipes with logical AND and OR
operators. Note that the evaluation order is always from left to right
(left-associative), both operators have the same precedence, and are
short-circuiting. Note, however, that short-circuiting does not apply to
expansions (variable, function calls, evaluation contexts). The logical result
of a command expression is the result of the last command pipe executed.

A command pipe can combine several commands with a pipe (\c{stdout} of the
left-hand-side command is connected to \c{stdin} of the right-hand-side). The
logical result of a command pipe is the logical AND of all its commands.

A command begins with a command path followed by options/arguments, redirects,
and cleanups, all optional and in any order.

A command may specify an exit code check. If executing a command results in
an abnormal process termination, then the whole outer construct (e.g., test,
setup/teardown, etc) summarily fails. Otherwise (that is, in case of a normal
termination), the exit code is checked. If omitted, then the test is expected
to succeed (0 exit code). The logical result of executing a command is
therefore a boolean value which is used in the higher-level constructs (pipe
and expression).

Note that \c{command-loop-flow} is only valid inside the \c{command-for} and
\c{command-while} loop constructs. The \c{continue} line interrupts the
current iteration of the nearest containing loop and starts the next
iteration, subject to the normal \c{for} and \c{while} loop termination
semantics. The \c{break} line interrupts the current iteration and terminates
the loop.


\h#syntax-command-if|Command-If|

\
command-if:
  ('if'|'if!') command-line | \
  ('ifn'|'ifn!'|'ife'|'ife!') value-line
  command-block|command-or-variable
  *command-elif
  ?command-else

command-block:
  '{'
  *(command-or-variable|directive)
  '}'

command-or-variable:
  variable-line|command-like

command-elif:
  ('elif'|'elif!') command-line | \
  ('elifn'|'elifn!'|'elife'|'elife!') value-line
  command-block|command-or-variable

command-else:
  'else'
  command-block|command-or-variable
\

A group of commands can be executed conditionally. The condition
\c{command-line} is executed in the context of the test scope the
\c{command-if} construct belongs to. Similarly, the condition \c{value-line}
is expanded in the context of the mentioned test scope. See \l{#syntax-if
Group/Test/Variable/Command If} for details on the semantics.

Note that in a compound test, commands inside \c{command-if} must not end with
\c{;}. Rather, \c{;} may follow \c{command-if}. For example:

\
if ($cxx.target.class == 'windows')
{
  foo = windows
  setup1
  setup2
}
else
{
  foo = posix
};
if ($cxx.id == 'clang')
  setup3;
test1 $foo
\

You may have noticed that the grammar may match a standalone \c{if} flow
control construct ambiguously, with both \c{test-if} and \c{command-if}
production rules. In such cases the \c{test-if} rule takes precedence. For
example:

\
# variable-if
#
if foo
  bar = BAR

# test-if
#
: test1
if foo
  $* $bar

# command-if
#
if foo
  $* $bar : test2

# command-if
#
: test3
if foo
  $* $bar;
baz
\

The \c{test-if} construct differs from \c{command-if} in that its condition
\c{command-line} is executed in the context of the group scope containing the
test scope. Similarly, for c{test-if}, the condition \c{value-line} is
expanded in the context of the mentioned group scope.

Below is the version of the above example that also shows all the implicit
scopes with annotations that explain which scope the commands and variable
assignments are executed in:

\
{{
  if foo        # group scope
    bar = BAR   # group scope

  : test1
  if foo        # group scope
  {
    $* $bar     # test scope
  }

  : test2
  {
    if foo      # test scope
      $* $bar   # test scope
  }

  : test3
  {
    if foo      # test scope
      $* $bar   # test scope
    baz         # test scope
  }
}}
\


\h#syntax-command-for|Command-For|

\
command-for:
  command-for-value|command-for-stream

command-for-value:
  'for' <variable-name> element-attributes? ':' value-line
  command-block|command-or-variable

command-for-stream:
  (command-pipe '|')? \
  'for' (<opt>|stdin)* <variable-name> element-attributes? (stdin)*
  command-block|command-or-variable
\

A group of commands can be executed in a loop while iterating over elements of
a list and setting the specified variable (called \i{loop variable}) to the
corresponding element on each iteration. At the end of the iteration the loop
variable contains the value of the last element, if any. Note that in a
compound test, commands inside \c{command-for} must not end with
\c{;}. Rather, \c{;} may follow \c{command-for}.

The \c{for} loop has two forms: In the first form the list is specified as
arguments. Similar to the \c{for} loop in the Buildfile language, it can
contain variable expansions, function calls, evaluation contexts, and/or
literal values. For example:

\
for v: $values
{
  test1 $v
  test2 $v
};
test3
\

In the second form the list is read from the \c{stdin} input. The input data
is split into elements either at whitespaces (default) or newlines, which can
be controlled with the \c{-n|--newline} and \c{-w|--whitespace} options.
Overall, this form supports the same set of options as the \l{#builtins-set
\c{set}} pseudo-builtin. For example:

\
cat values.txt | for -n v
  test1 $v;
test2
\

Or using the \c{stdin} redirect:

\
for -n v <=values.txt
  test1 $v;
test2
\

Both forms can include value attributes enclosed in \c{[]} to be applied to
each element, again similar to the \l{#builtins-set \c{set}} pseudo-builtin.


\h#syntax-command-while|Command-While|

\
command-while:
  'while' command-line
  command-block|command-or-variable
\

A group of commands can be executed in a loop while a condition evaluates to
\c{true}. The condition \c{command-line} semantics is the same as in
\c{command-if}. Note that in a compound test, commands inside
\c{command-while} must not end with \c{;}. Rather, \c{;} may follow
\c{command-while}. For example:

\
i = [uint64] 0;
n = $size($values);
while ($i != $n)
{
  test1 ($values[$i])
  i += 1
};
test2
\

Another example:

\
while test -f $file
  test1 $file;
test2
\


\h#syntax-redirect|Redirect|

\
redirect: stdin|stdout|stderr

stdin:  '0'?(in-redirect)
stdout: '1'?(out-redirect)
stderr: '2'(out-redirect)
\

In redirects the file descriptors must not be separated from the redirect
operators with whitespaces. And if leading text is not separated from the
redirect operators, then it is expected to be the file descriptor. As an
example, the first command below has \c{2} as an argument (and therefore
redirects \c{stdout}, not \c{stderr}). While the second is invalid since
\c{a1} is not a valid file descriptor.

\
$* 2 >-
$* a1>-
\


\h#syntax-in-redirect|Input Redirect|

\
in-redirect:  '<-'|\
              '<|'|\
              ('<<<'|'<=') <file>|\
              ('<<'|'<<='){':'?'/'?} <here-end>|\
              ('<'|'<<<='){':'?'/'?} <text>
\

The \c{stdin} data can come from a pipe, here-string (\c{<}), here-document
(\c{<<}), a file (\c{<<<}), or \c{/dev/null}-equivalent (\c{<-}). Specifying
both a pipe and a redirect is an error. If no pipe or \c{stdin} redirect is
specified and the test tries to read from \c{stdin}, it is considered to have
failed (unexpected input). However, whether this is detected and diagnosed is
implementation-defined. To allow reading from the default \c{stdin} (for
instance, if the test is really an example), the \c{<|} redirect is used.

\N|The \c{<=}, \c{<<=}, and \c{<<<=} redirects are a stable syntax across
various \c{build2} scripting language flavors (Testscript, Buildscript,
etc). While the \c{<}, \c{<<}, and \c{<<<} redirects are their Testscript
aliases with the mapping chosen to be more convenient for this flavor of the
scripting language. This mapping is as follows:

\
<    <<<=  here-string
<<   <<=   here-document
<<<  <=    file
\

|

Here-string and here-document redirects may specify the following redirect
modifiers:

The \c{:} modifier is used to suppress the otherwise automatically-added
terminating newline.

The \c{/} modifier causes all the forward slashes in the here-string or
here-document to be translated to the directory separator of the test target
platform (as indicated by \c{test.target}).

A here-document redirect must be specified \i{literally} on the command
line. Specifically, it must not be the result of an expansion (which rarely
makes sense anyway since the following here-document fragment itself cannot be
the result of an expansion either). See \l{#syntax-here-document Here Document}
for details.


\h#syntax-in-output|Output Redirect|

\
out-redirect: '>-'|\
              '>|'|\
              '>!'|\
              '>=' <file>|\
              '>+' <file>|\
              '>&' ('1'|'2')|\
              ('>>>'|'>?') <file>|\
              ('>>'|'>>?'){':'?'/'?}'~'? <here-end>|\
              ('>'|'>>>?'){':'?'/'?}'~'? <text>
\

The \c{stdout} and \c{stderr} data can go to a pipe (\c{stdout} only), file
(\c{>=} to overwrite and \c{>+} to append), or \c{/dev/null}-equivalent
(\c{>-}). It can also be compared to a here-string (\c{>}), a here-document
(\c{>>}), or a file contents (\c{>>>}). For \c{stdout} specifying both a pipe
and a redirect is an error. A test that tries to write to an un-redirected
stream (either \c{stdout} or \c{stderr}) is considered to have failed
(unexpected output). To allow writing to the default \c{stdout} or \c{stderr}
(for instance, if the test is really an example), the \c{>|} redirect is used.

\N|The \c{>?}, \c{>>?}, and \c{>>>?} redirects are a stable syntax across
various \c{build2} scripting language flavors (Testscript, Buildscript,
etc). While the \c{>}, \c{>>}, and \c{>>>} redirects are their Testscript
aliases with the mapping chosen to be more convenient for this flavor of the
scripting language. This mapping is as follows:

\
>    >>>?  here-string comparison
>>   >>?   here-document comparison
>>>  >?    file contents comparison
\

|

The \c{>!} redirect acts like \c{>-} if the build system verbosity level is
below 2 and as \c{>|} otherwise. It is normally used to ignore diagnostics (as
opposed to data) during normal operation but to still be able to examine it,
for example, when debugging a failing test.

It is also possible to merge \c{stderr} to \c{stdout} or vice versa with a
merge redirect (\c{>&}). In this case the left-hand-side descriptor (implied
or explicit) must not be the same as the right-hand-side. Having both merge
redirects at the same time is an error.

The \c{:} and \c{/} redirect modifiers have the same semantics as in the input
redirects. The \c{~} modifier is used to indicate that the following
here-string/here-document is a regular expression (see \l{#syntax-regex Regex})
rather than a literal. Note that if present, it must be specified last.

Similar to the input redirects, an output here-document redirect must be
specified literally on the command line. See \l{#syntax-here-document Here
Document} for details.


\h#syntax-here-document|Here-Document|

\
here-document:
  *<text>
  <here-end>
\

A here-document can be used to supply data to \c{stdin} or to compare output
to the expected result for \c{stdout} and \c{stderr}. The order of
here-document fragments must match the order of redirects, for example:

\
: select-no-table-error
$* --interactive >>EOO <<EOI 2>>EOE
enter query:
EOO
SELECT * FROM no_such_table
EOI
error: no such table 'no_such_table'
EOE
\

Two or more here-document redirects can use the same end marker. In this case
all the redirects must have the same modifiers, if any. Only the here-document
fragment corresponding to the first occurrence of the end marker must be
present (called \i{shared} here-document) with the subsequent redirects
reusing the same data. This mechanism is primarily useful for round-trip
testing, for example:

\
: xml-round-trip
$* <<EOD >>EOD
<hello>Hello, World!</hello>
EOD
\

Here-strings can be single-quoted literals or double-quoted with expansion.
This semantics is extended to here-documents as follows: If the end marker
on the command line is single-quoted, then the here-document lines are
parsed as if they were single-quoted except that the single quote itself
is not treated as special. In this mode there are no expansions, escape
sequences, not even line continuations \- each line is taken literally.

If the end marker on the command line is double-quoted, then the here-document
lines are parsed as if they were double-quoted except that the double quote
itself is not treated as special. In this mode we can use variable
expansions, function calls, and evaluation contexts. However, we have to
escape the \c{$(\\} character set.

If the end marker is not quoted then it is treated as if it were
single-quoted. Note also that quoted end markers must be quoted entirely,
that is, from the beginning and until the end and without any interruptions.

Here-document fragments can be indented. The leading whitespaces of the end
marker line (called \i{strip prefix}) determine the indentation. Every other
line in the here-document should start with this prefix which is then
automatically stripped. The only exception is a blank line. For example, the
following two testscripts are equivalent:

\
{
  $* <<EOI
  foo
    bar
  EOI
}
\

\
{
  $* <<EOI
foo
  bar
EOI
}
\

Note, however, that the leading whitespace stripping does not apply to line
continuations.


\h#syntax-regex|Output Regex|

Instead of literal text the expected result in output here-strings and
here-documents can be specified as ECMAScript regular expressions, more
precisely, ECMA-262-based C++11 regular expressions. To signal the use of
regular expressions the redirect must end with the \c{~} modifier, for
example:

\
$* >~'/fo+/' 2>>~/EOE/
/ba+r/
baz
EOE
\

The regular expression used for output matching is \i{two-level}. At the outer
level the expression is over lines with each line treated as a single
character. We will refer to this outer expression as \i{line-regex} and to its
characters as \i{line-char}.

A line-char can be a literal line (like \c{baz} in the example above) in which
case it will only be equal to an identical line in the output. Alternatively, a
line-char can be an inner level regex (like \c{ba+r} above) in which case it
will be equal to any line in the output that matches this regex.  Where not
clear from context we will refer to this inner expression as \i{char-regex}
and its characters as \i{char}.

A line is treated as literal unless it starts with the \i{regex introducer
character} (\c{/} in the above example). In contrast, the line-regex is always
in effect (in a sense, the \c{~} modifier is its introducer). Note that the
here-string regex naturally (since there is only one line) must start with an
introducer.

A char-regex line that starts with an introducer must also end with one
optionally followed by \i{match flags}, for example:

\
$* >>~/EOO/
/ba+r/i
/ba+z/i
EOO
\

The following match flags are recognized:

\dl|

\li|\n\c{i}

  Perform case-insensitive match.|

\li|\n\c{d}

  Invert the dot character (\c{.}) escaping. With this flag unescaped dots
  are treated as literal characters while the escaped ones (\c{\\.}) \-
  as matching any character. Note that dots specified within character
  classes (\c{[.]}) are not affected.||

Any character can act as a regex introducer. For here-strings it is the first
character in the string. For here-documents the introducer is specified as
part of the end marker. In this case the first character is the introducer,
everything after that and until the second occurrence of the introducer is the
actual end marker, and everything after that are global match flags. Global
match flags apply to every char-regex (but not literal lines or the line-regex
itself) in this here-document. Note that there is no way to escape the
introducer character inside the regex.

As an example, here is a shorter version of the previous example that also
uses a different introducer character.

\
$* >>~%EOO%i
%ba+r%
%ba+z%
EOO
\

A line-char is treated as an ordinary, non-syntax character with regards to
the outer-level line-regex. Lines that start with a regex introducer but do
not end with one are used to specify syntax line-chars. Such syntax line-chars
can also be specified after (or instead of) match flags. For example:

\
$* >>~/EOO/
/(
/fo+x/|
/ba+r/|
/ba+z/
/)+
EOO
\

As an illustration, if we call the \c{/fo+x/} expression \c{A}, \c{/ba+r/} \-
\c{B}, and \c{/ba+z/} \- C, then we can represent the above line-regex in
the following more traditional form:

\
(A|B|C)+
\

Only characters from the \c{.()|*+?{\}\\0123456789,=!} set are allowed as
syntax line-chars with the presence of any other characters being an error.

A blank line as well as the \c{//} sequence (assuming \c{/} is the introducer)
are treated as an empty line-char. For the purpose of matching, newlines are
viewed as separators rather than being part of a line. In particular, in this
model, the customary trailing newline at the end of the output introduces a
trailing empty line-char. As a result, unless the \c{:} (no newline) redirect
modifier is used, an empty line-char is implicitly added at the end of
line-regex.


\h#syntax-cleanup|Cleanup|

\
cleanup: ('&'|'&?'|'&!') (<file>|<dir>)
\

If a command creates extra files or directories, then they can be registered
for automatic cleanup at the end of the scope (test or group). Files mentioned
in redirects are registered automatically. Additionally, certain builtins (for
example \c{touch} and \c{mkdir}) also register their output files/directories
automatically (as described in each builtin's documentation).

If the path ends with a directory separator (slash), then it is assumed to be
a directory. Otherwise \- a file. A directory about to be removed must be
empty (no unexpected output).

The \c{&} syntax registers a normal or \i{always} cleanup: the test fails if
the file/directory does not exist. The \c{&?} syntax is a \i{maybe} cleanup:
the file/directory is removed if it exists. Finally, \c{&!} is a \i{never}
cleanup: it disables a previously registered cleanup for this file/directory
(primarily used to disable automatic cleanups registered by builtins).

The path components may contain the \c{*} and \c{?} wildcard characters
with the following semantics:

\
?    - any single character
*    - all immediate files
*/   - all immediate sub-directories (which must be empty)
**   - all files recursively
**/  - all sub-directories recursively (which must be empty)
***/ - all sub-directories recursively (which must be empty)
       as well as the start directory itself
\

In addition, if the last component in the path is \c{***} (without trailing
directory separator), then it matches all files and sub-directories
recursively as well as the start directory itself. For example, the following
cleanup will remove \c{dir/} and its content recursively.

\
$* &dir/***
\

Registering a path for cleanup that is outside the script working directory is
an error. You can, however, clean them up manually with \c{rm/rmdir -f}.


\h1#builtins|Builtins|

The Testscript language provides a portable subset of POSIX utilities as
builtins. Each utility normally implements the commonly used subset of the
corresponding POSIX specification, though there are deviations (for example,
in option handling) and extensions, as described in this chapter. Note also
that the builtins are implemented in-process with some of the simple ones
such as \c{true/false}, \c{mkdir}, etc., being just function calls.

To run a system utility instead of a builtin prefix its name with \c{^}, for
example:

\
^cat --squeeze-blank <file>
\


\h#builtins-cat|\c{cat}|

\
cat <file>...
\

Read files in order and write their contents to \c{stdout}. Read from
\c{stdin} if no file is specified or \c{-} is specified as the file name.


\h#builtins-cp|\c{cp}|

\
cp [-p] [--no-cleanup]        <src-file>     <dst-file>
cp [-p] [--no-cleanup] -R|-r  <src-dir>      <dst-dir>
cp [-p] [--no-cleanup]        <src-file>...  <dst-dir>/
cp [-p] [--no-cleanup] -R|-r  <src-path>...  <dst-dir>/
\

Copy files and/or directories. The first two forms make a copy of a single
entity at the specified path. The last two copy one or more entities into the
specified directory.

If the last argument does not end with a directory separator and the \c{-R} or
\c{-r} option is not specified, then the first synopsis is assumed where
\c{cp} copies \i{src-file} as \i{dst-file} failing if the \i{src-file}
filesystem entry does not exist or if either filesystem entry is a directory.

If the last argument does not end with a directory separator and the \c{-R} or
\c{-r} option is specified, then the second synopsis is assumed where \c{cp}
copies \i{src-dir} as \i{dst-dir} failing if the \i{src-dir} filesystem entry
does not exist or is not a directory or if the \i{dst-dir} filesystem entry
already exists.

In both these cases \c{cp} also fails if more than two arguments are
specified.

If the last argument ends with a directory separator and the \c{-R} or \c{-r}
option is not specified, then the third synopsis is assumed where \c{cp}
copies one or more \i{src-file} files into the \i{dst-dir} directory as if by
executing the following command for each file:

\
cp src-file dst-dir/src-name
\

Where \i{src-name} is the last path component in \i{src-file}.

In this case \c{cp} fails if a filesystem entry for any of the \i{src-file}
files does not exist or is a directory or if the \i{dst-dir} filesystem entry
does not exist or is not a directory.

Finally, if the last argument ends with a directory separator and the \c{-R}
or \c{-r} option is specified, then the last synopsis is assumed where \c{cp}
copies one or more \i{src-path} files or directories into the \i{dst-dir}
directory as if by executing the following command for each file:

\
cp src-path dst-dir/src-name
\

And the following command for each directory:

\
cp -R src-path dst-dir/src-name
\

Where \i{src-name} is the last path component in \i{src-path}. The
determination of whether \i{src-path} is a file or directory is done by
querying the filesystem entry type.

In this case \c{cp} fails if a filesystem entry for any of the \i{src-path}
files/directories does not exist or if the \i{dst-dir} filesystem entry does
not exist or is not a directory. For a \i{src-path} directory \c{cp} also fails
if the \i{dst-dir/src-name} filesystem entry already exists.

\dl|

\li|\n\c{-R|-r|--recursive}

  Copy directories recursively.|

\li|\n\c{-p|--preserve}

  Copy permissions as well as modification and access times.||

Unless the \c{--no-cleanup} option is specified, newly created files and
directories that are inside the script working directory are automatically
registered for cleanup.


\h#builtins-date|\c{date}|

\
date [-u] [+<format>]
\

Print the local time or, if the \c{-u} option is specified, the Coordinated
Universal Time (UTC) in the specified format.

The optional \i{format} argument is the \c{std::put_time()} C++11
manipulator's format string that in addition supports the nanoseconds
specifier in the form \c{\b{%[}\i{<d>}\b{N]}} where \ci{<d>} is the optional
single delimiter character, for example \c{.}. If the nanoseconds part is 0,
then it is not printed (nor the delimiter character). Otherwise, the
nanoseconds part is padded to 9 characters with leading zeros.

Note that this builtin's format specifier set is a superset of the POSIX
\c{date} utility.

If the \i{format} argument is not specified, then
\c{%a\ %b\ %e\ %H:%M:%S\ %Z\ %Y} is used by default.

\dl|

\li|\n\c{-u|--utc}

  Print Coordinated Universal Time (UTC).||


\h#builtins-diff|\c{diff}|

\
diff [-u|-U <num>] <file1> <file2>
\

Compare the contents of \i{file1} and \i{file2}.

The \c{diff} utility is not a builtin. Instead, the test platform is expected
to provide a (reasonably) POSIX-compatible implementation. It should at least
supports the \c{-u} and \c{-U} options and recognize the \c{-} file name as
an instruction to read from \c{stdin}. On Windows, GNU \c{diff} can be assumed
(provided as part of the \c{build2} toolchain).

\dl|

\li|\n\c{-u}

  Produce output in the unified format.|

\li|\n\c{-U <num>}

  Produce output in the unified output format with \i{num} lines of context.||


\h#builtins-echo|\c{echo}|

\
echo <string>...
\

Write strings to \c{stdout} separating them with a single space and ending
with a newline.


\h#builtins-env|\c{env}|

\
env [-t <sec>] [-c <dir>] [-u <name>]... [-] [<name>=<value>]... -- \
    <cmd>
\

Run a command limiting its execution time, changing its working directory,
and/or adding/removing the variables to/from the environment.

Note that \c{env} is a \i{pseudo-builtin}. In particular, its name and the
\c{--} separator must be specified \i{literally} on the command line.
Specifically, they must not be the result of an expansion. Also note that the
\c{--} separator must always be present.

To avoid ambiguity, the variable assignments can be separated from the options
with the explicit \c{-} separator. In the example below the \c{--unset}
variable is added to the environment:

\
env - --unset=FOO -- $*
\

\dl|

\li|\n\c{-t|--timeout <sec>}

  Terminate the command if it fails to complete within the specified number
  of seconds. See also the \l{#builtins-timeout \c{timeout}} builtin.|

\li|\n\c{-s|--timeout-success}

  Assume the command terminated due to the timeout specified with the
  \c{-t|--timeout} option to have succeeded.|

\li|\n\c{-c|--cwd <dir>}

  Change the command's working directory.|

\li|\n\c{-u|--unset <name>}

  Remove the specified variable from the environment.||

See also the \l{#builtins-export \c{export}} builtin.


\h#builtins-exit|\c{exit}|

\
exit [<code>] [<diagnostics>]
\

Exit the current group or test scope skipping any remaining commands.

Note that \c{exit} is a \i{pseudo-builtin}. In particular, it must be the only
command in the pipe expression and its standard streams cannot be redirected.

If the zero code is specified, then \c{exit} exits the current scope
successfully. In this case, if exiting a group scope, teardown commands and
cleanups are executed normally.

If a non-zero code is specified, then \c{exit} exits the current scope and all
the outer scopes unsuccessfully, as if the \c{exit} command failed. In this
case the diagnostics string describing the error can be specified as a second
argument. It will be printed with the \c{error:\ } prefix to \c{stderr}.

If no exit code is specified, then assume exit code 1, if the diagnostics
string is specified, and 0 otherwise.

The exit code must be in the 0-255 range.


\h#builtins-export|\c{export}|

\
export [-c <name>]... [-u <name>]... [<name>=<value>]...
\

Add/remove the variables to/from the current scope commands execution
environment and/or clear the previous additions/removals.

Note that \c{export} is a \i{pseudo-builtin}. In particular, it must be the
only command in the pipe expression, it either succeeds or terminates
abnormally, and its standard streams cannot be redirected.

The environment variables can be added and removed on multiple levels: with
the \c{export} builtin in the nested test group scopes and the test scope and
with the \l{#builtins-env \c{env}} builtin for individual commands. Before
executing a command, all the variable additions and removals from its
environment hierarchy are merged so that those specified in the inner levels
override those specified in the outer levels.

\dl|

\li|\n\c{-c|--clear <name>}

  Clear the previous variable addition/removal to/from the environment, if
  exists.|

\li|\n\c{-u|--unset <name>}

  Remove the specified variable from the environment.||


\h#builtins-false|\c{false}|

\
false
\

Do nothing and terminate normally with the 1 exit code (indicating failure).


\h#builtins-find|\c{find}|

\
find <start-path>... [<expression>]
\

Search for filesystem entries in a filesystem hierarchy. Traverse filesystem
hierarchies from each \i{start-path} specified on the command line, evaluate
for each filesystem entry the boolean \i{expression} consisting of the
options-like arguments called \i{primaries}, and print the filesystem entry
path if it evaluates to \c{true}, one path per line. The primaries are
combined into the expression with an implicit logical AND operator. The empty
expression always evaluates to \c{true}.

Note that the implementation deviates from POSIX in a number of ways. It only
supports a small subset of primaries and doesn't support compound expressions,
negations, logical OR and (explicit) AND operators, and the \c{-type} primary
values other than \c{f}, \c{d}, and \c{l}. It, however, supports the
\c{-mindepth} and \c{-maxdepth} primaries which are not specified by POSIX but
are supported by the major \c{find} utility implementations. Likewise, it
dereferences symlinks in <start-path> if it ends with a trailing directory
separator.

The following primaries are supported:

\dl|

\li|\n\c{-name <pattern>}

  Evaluates to \c{true} if a filesystem entry base name matches the specified
  wildcard pattern.|

\li|\n\c{-type <type>}

  Evaluates to \c{true} if a filesystem entry type matches the specified type:
  \c{f} for a regular file, \c{d} for a directory, and \c{l} for a symbolic
  link.|

\li|\n\c{-mindepth <depth>}

  Evaluates to \c{true} if a filesystem entry directory level is not less than
  the specified depth. The level of the \i{start-path} entries specified on
  the command line is 0.|

\li|\n\c{-maxdepth <depth>}

  Evaluates to \c{true} if a filesystem entry directory level is not greater
  than the specified depth. The level of the \i{start-path} entries specified
  on the command line is 0. Note that the implementation is smart enough not
  to traverse a directory when the maximum depth is reached.||


\h#builtins-ln|\c{ln}|

\
ln [--no-cleanup] [-s] <target-path>    <link-path>
ln [--no-cleanup] [-s] <target-path>... <dir>/
\

Create hard links to files (default) or symbolic links to files and/or
directories (if \c{-s|--symbolic} is specified). The first form creates a
single target link at the specified path. The second form creates links to one
or more targets inside the specified directory.

If the last argument does not end with a directory separator, then the first
synopsis is assumed where \c{ln} creates the link to \i{target-path} at
\i{link-path} failing if the \i{target-path} filesystem entry does not exist,
\i{link-path} filesystem entry already exists, or more than two arguments are
specified. For symbolic links, if \i{target-path} is relative, then it is
assumed to be relative to the \i{link-path}'s directory.

If the last argument ends with a directory separator, then the second synopsis
is assumed where \c{ln} creates one or more links to \i{target-path} files or
directories inside the \i{dir} directory as if by executing the following
command for each target:

\
ln [-s] target-path dir/target-name
\

Where \i{target-name} is the last path component in \i{target-path}.

For both cases \c{ln} falls back to creating a hard link if symbolic link
creation is not supported. If hard link creation is not supported either,
then \c{ln} falls back to copying the content, recursively in case of a
directory target.

\dl|

\li|\n\c{-s|--symbolic}

  Create symbolic links.||

Unless the \c{--no-cleanup} option is specified, created filesystem entries
that are inside the script working directory are automatically registered for
cleanup.


\h#builtins-mkdir|\c{mkdir}|

\
mkdir [--no-cleanup] [-p] <dir>...
\

Create directories. Unless the \c{-p} option is specified, all the leading
directories must exist and the directory itself must not exist.

\dl|

\li|\n\c{-p|--parents}

  Create missing leading directories and ignore directories that already
  exist.||

Unless the \c{--no-cleanup} option is specified, newly created directories
(including the leading ones) that are inside the script working directory are
automatically registered for cleanup.


\h#builtins-mv|\c{mv}|

\
mv [--no-cleanup] [-f] <src-path>    <dst-path>
mv [--no-cleanup] [-f] <src-path>... <dst-dir>/
\

Rename or move files and/or directories.

The first form moves an entity to the specified path. The parent directory of
the destination path must exist. An existing destination entity is replaced
with the source if they are both either directories or non-directories (files,
symlinks, etc). In the former case the destination directory must be empty.
The source and destination paths must not be the same nor be the test working
directory or its parent directory. The source path must also not be outside
the script working directory unless the \c{-f} option is specified.

The second form moves one or more entities into the specified directory as if
by executing the following command for each entity:

\
mv src-path dst-dir/src-name
\

Where \i{src-name} is the last path component in \i{src-path}.

\dl|

\li|\n\c{-f|--force}

  Do not fail if a source path is outside the script working directory.||

Unless the \c{--no-cleanup} option is specified, the cleanups registered for
the source entities are adjusted according to their new names and/or
locations. If the destination entity already exists or is outside the test
working directory then the source entity cleanup is canceled. Otherwise the
source entity cleanup path is replaced with the destination path. If the
source entity is a directory, then, in addition, cleanups that are sub-paths
of this directory are made sub-paths of the destination directory.

Note that the implementation deviates from POSIX in a number of ways. It never
interacts with the user and fails immediately if unable to act on an argument.
It does not check for dot containment in the path nor considers filesystem
permissions. In essence, it simply tries to move the filesystem entry.


\h#builtins-rm|\c{rm}|

\
rm [-r] [-f] <path>...
\

Remove filesystem entries. To remove a directory (even empty) the \c{-r}
option must be specified.

The path must not be the test working directory or its parent directory. It
also must not be outside the script working directory unless the \c{-f} option
is specified.

\dl|

\li|\n\c{-r|--recursive}

  Remove directories and their contents recursively.|

\li|\n\c{-f|--force}

  Do not fail if no path is specified, the path does not exist, or is outside
  the script working directory.||

Note that the implementation deviates from POSIX in a number of ways. It never
interacts with the user and fails immediately if unable to act on an argument.
It does not check for dot containment in the path nor considers filesystem
permissions. In essence, it simply tries to remove the filesystem entry.


\h#builtins-rmdir|\c{rmdir}|

\
rmdir [-f] <dir>...
\

Remove directories. The directory must be empty and not be the test working
directory or its parent directory. It also must not be outside the script
working directory unless the \c{-f} option is specified.

\dl|

\li|\n\c{-f|--force}

  Do not fail if no directory is specified, the directory does not exist, or
  is outside the script working directory.||


\h#builtins-sed|\c{sed}|

\
sed [-n] [-i] (-e <script>)... [<file>]
\

Read text from \i{file}, make editing changes according to \i{script}, and
write the result to \c{stdout}. If multiple \i{scripts} are present, then they
are applied in the order specified. If \i{file} is not specified or is \c{-},
read from \c{stdin}. If both \i{file} and the \c{-i} option are specified then
edit the \i{file} in place. Specifying \c{-i} when reading from \c{stdin} is
illegal.

Note that this builtin implementation deviates substantially from POSIX
\c{sed} (as described next). Most significantly, the regular expression flavor
is ECMAScript, more precisely, ECMA-262-based C++11 regular expressions. Note
that the \c{match_not_null} flag is in effect unless the line being matched
is empty.

\dl|

\li|\n\c{-n|--quiet}

  Suppress automatic printing of the pattern space at the end of the script
  execution.|

\li|\n\c{-i|--in-place}

  Edit \i{file} in place.|

\li|\n\c{-e|--expression <script>}

  Editing commands to be executed. At least one script must be specified.||

To perform the transformation \c{sed} reads each line of input (without the
newline) into the pattern space. It then executes the script commands on the
pattern space. At the end of the script execution, unless the \c{-n} option is
specified, \c{sed} writes the pattern space to output followed by a newline.

Currently, only single-command scripts using the following editing commands
are supported.

\dl|

\li|\n\c{s/<regex>/<replacement>/<flags>}\n

  Match \i{regex} against the pattern space. If successful, replace the part
  of the pattern space that matched with \i{replacement}. If the \c{g} flag is
  present in \i{flags} then continue substituting subsequent matches of
  \i{regex} in the same pattern space. If the \c{p} flag is present in
  \i{flags} and the replacement has been made, then write the pattern space to
  \c{stdout} and start the next cycle by proceeding to read the next line
  of input. If both \c{g} and \c{p} were specified, then write the pattern
  space out only after the last substitution.

  Any character other than \c{\\} (backslash) or newline can be used instead
  of \c{/} (slash) to delimit \i{regex}, \i{replacement}, and \i{flags}. Note
  that no escaping of the delimiter character is supported.

  If \i{regex} starts with \c{^}, then it only matches at the beginning of the
  pattern space. Similarly, if it ends with \c{$}, then it only matches at the
  end of the pattern space. If the \c{i} flag is present in \i{flags}, then
  the match is performed in a case-insensitive manner.

  In \i{replacement}, besides the standard ECMAScript escape sequences
  (\c{$1}, \c{$2}, \c{$&}, etc), the following additional sequences are
  recognized:

  \
    \N - Nth capture, where N is in the 1-9 range.

    \u - Convert next character to the upper case.
    \l - Convert next character to the lower case.

    \U - Convert next characters until \E to the upper case.
    \L - Convert next characters until \E to the lower case.

    \n - Newline.
    \\\\ - Literal backslash.
  \

  Note that unlike POSIX semantics, just \c{&} does not have a special meaning
  in \i{replacement}.||


\h#builtins-set|\c{set}|

\
set [-e] [-n|-w] <var> [<attr>]
\

Set variable from the \c{stdin} input.

Note that \c{set} is a \i{pseudo-builtin}. In particular, it must be the last
command in the pipe expression, it either succeeds or terminates abnormally,
and its \c{stderr} cannot be redirected. Note also that all the variables on
the command line are expanded before any \c{set} commands are executed, for
example:

\
foo = foo
echo 'bar' | set foo && echo $foo  # foo
echo $foo                          # bar
\

Unless the \c{-e} option is specified, a single final newline is ignored in
the input.

If the \c{-n} option is specified, then the input is split into a list of
elements at newlines, including a final blank element in case of \c{-e}.
Multiple consecutive newlines are not collapsed.

If the \c{-w} option is specified, then the input is split into a list of
elements at whitespaces, including a final blank element in case of \c{-e}. In
this mode if \c{-e} is not specified, then all (and not just newline) trailing
whitespaces are ignored. Multiple consecutive whitespaces (including newlines)
are collapsed.

If neither \c{-n} nor \c{-w} is specified, then the entire input is used as a
single element, including a final newline in case of \c{-e}.

If the \i{attr} argument is specified, then it must contain a list of value
attributes enclosed in \c{[]}, for example:

\
sed -e 's/foo/bar/' input | set x [string]
\

Note that this is also the only way to set a variable with a computed name,
for example:

\
foo = FOO
set $foo [null] <-
\

\dl|

\li|\n\c{-e|--exact}

  Do not ignore the final newline.|

\li|\n\c{-n|--newline}

  Split the input into a list of elements at newlines.|

\li|\n\c{-w|--whitespace}

  Split the input into a list of elements at whitespaces.||


\h#builtins-sha256sum|\c{sha256sum}|

\
sha256sum [-b|-t] [--sum-only] <file>...
\

Read files in order, compute their SHA256 checksums, and print them to
\c{stdout}, one per line. Read from \c{stdin} if no file is specified or \c{-}
is specified as the file name.

Unless the \c{-b} option is specified, the files are read in the text mode. On
POSIX systems the binary and text modes are the same. On Windows, when reading
in the text mode the sequence of \c{0xD}, \c{0xA} characters is translated
into the single \c{OxA} character and \c{0x1A} is interpreted as EOF.

Unless the \c{--sum-only} option is specified, then a line in the following
form is printed for each file:

\
  <checksum> (*| )<path>
\

The \c{*} character is printed in the binary mode and the space character in
the text mode.

If the \c{--sum-only} option is specified, then only the checksum is printed
for each file, one per line.

Note that the implementation only supports a subset of the GNU \c{sha256sum}
utility options but extends it with the \c{--sum-only} option.

\dl|

\li|\n\c{-b|--binary}

  Read files in binary mode.|

\li|\n\c{-t|--text}

  Read files in text mode.|

\li|\n\c{--sum-only}

  Print only file checksums.||

See also the \l{#builtins-xxh64sum \c{xxh64sum}} builtin for a faster but
non-cryptographic alternative.


\h#builtins-sleep|\c{sleep}|

\
sleep <seconds>
\

Suspend the current test or test group execution for at least the specified
number of seconds. Note that in order to improve resource utilization, the
implementation may sleep longer than requested, potentially significantly.


\h#builtins-test|\c{test}|

\
test -f|-d <path>
\

Test the specified \i{path} according to one of the following options. Succeed
(0 exit code) if the test passes and fail (non-0 exit code) otherwise.

\dl|

\li|\n\c{-f|--file}

  Path exists and is to a regular file.|

\li|\n\c{-d|--directory}

  Path exists and is to a directory.||

Note that tests dereference symbolic links.


\h#builtins-timeout|\c{timeout}|

\
timeout [-s] [<group-timeout>]/[<test-timeout>]
timeout [-s] <timeout>
\

Specify test and/or test group timeout.

The first form sets the test group and/or individual test timeouts and can
only be used as a setup command. Either of the timeouts (but not both) can be
omitted.

The second form sets the test group timeout if used as a setup or teardown
command and the remaining test fragment timeout if used as a test command.

In both forms the timeouts are specified in seconds with the zero value
clearing the previously set timeout.

Note that \c{timeout} is a \i{pseudo-builtin}. In particular, it must be the
only command in the pipe expression, it either succeeds or terminates
abnormally, and its standard streams cannot be redirected.

The timeouts can be set on multiple levels: via the \c{config.test.timeout}
variable on the (potentially nested) project root scopes (see
\l{build2#module-test \c{test}} module for details), with the \c{timeout}
builtin in the nested test group scopes and the test scope, and with the
\l{#builtins-env \c{env}} builtin for individual commands. Each command must
complete before the nearest timeout from its timeout hierarchy. Failed that, a
command is terminated forcibly causing the entire \c{test} operation to fail
unless the expired timeout was specified with the \c{--success} option, in
which case the timed out command is assumed to have succeeded.

\dl|

\li|\n\c{-s|--success}

  Assume a command terminated due to this timeout to have succeeded.||


\h#builtins-touch|\c{touch}|

\
touch [--no-cleanup] [--after <ref-file>] <file>...
\

Change file access and modification times to the current time. Create files
that do not exist. Fail if a filesystem entry other than the file exists for
the specified name.

\dl|

\li|\n\c{--after <ref-file>}\n

  Keep touching the file until its modification time becomes after that of the
  specified reference file.||

Unless the \c{--no-cleanup} option is specified, newly created files that are
inside the script working directory are automatically registered for cleanup.


\h#builtins-true|\c{true}|

\
true
\

Do nothing and terminate normally with the 0 exit code (indicating success).


\h#builtins-xxh64sum|\c{xxh64sum}|

\
xxh64sum [-b|-t] [--sum-only] <file>...
\

Read files in order, compute their XXH64 checksums, and print them to
\c{stdout}, one per line. Read from \c{stdin} if no file is specified or \c{-}
is specified as the file name.

Note that the implementation deviates from the \c{xxh64sum} utility in a
number of ways instead following the \l{#builtins-sha256sum \c{sha256sum}}
builtin in regards to the command line interface and the output format.

Unless the \c{-b} option is specified, the files are read in the text mode
(see \l{#builtins-sha256sum \c{sha256sum}} builtin for details on the binary
and text modes on POSIX systems and Windows).

Unless the \c{--sum-only} option is specified, then a line in the following
form is printed for each file:

\
  <checksum> (*| )<path>
\

The \c{*} character is printed in the binary mode and the space character in
the text mode.

If the \c{--sum-only} option is specified, then only the checksum is printed
for each file, one per line.

\dl|

\li|\n\c{-b|--binary}

  Read files in binary mode.|

\li|\n\c{-t|--text}

  Read files in text mode.|

\li|\n\c{--sum-only}

  Print only file checksums.||

See also the \l{#builtins-sha256sum \c{sha256sum}} builtin for a slower but
cryptographic alternative.


\h1#style|Style Guide|

This chapter describes the testing guidelines and the Testscript style that is
used in the \c{build2} project.

The primary goal of testing in \c{build2} is not to exhaustively test every
possible situation. Rather, it is to keep tests comprehensible and
maintainable in the long run.

To this effect, don't try to test every possible combination; this striving
will quickly lead to everyone drowning in hundreds of tests that are only
slight variations of each other. Sometimes combination tests are useful but
generally keep things simple and test one thing at a time. The belief is
that real-world usage will uncover much more interesting interactions (which
must become regression tests) that you would never have thought of yourself.
To quote a famous physicist, \"\i{...  the imagination of nature is far, far
greater than the imagination of man.}\"

To expand on combination tests, don't confuse them with corner case tests. As
an example, say you have tests for feature A and B. Now you wonder what if for
some reason they don't work together. Note that you don't have a clear
understanding let alone evidence of why they might not work together; you just
want to add one more test, \i{for good measure}. We don't do that. To put it
another way, for each test you should have a clear understanding of what logic
in the code you are testing.

One approach that we found works well is to look at the diff of changes you
would like to commit and make sure you at least have a test that exercises
each \i{happy} (non-error) \i{logic branch}. For important code you may also
want to do so for \i{unhappy logic branches}.

It is also a good idea to keep testing in mind as you implement things. When
tempted to add a small special case just to make the result a little bit
\i{nicer}, remember that you will also have to test this special case.

If the functionality is well exposed in the program, prefer functional to unit
tests since the former test the end result rather than something intermediate
and possibly mocked. If unit-testing a complex piece of functionality,
consider designing a concise, textual \i{mini-format} for input (either via
command line or \c{stdin}) and output rather than constructing the test data
and expected results programmatically.

Documentation-wise, each test should at least include an explicit id that
adequately summarizes what it tests. Add a summary or even details for more
complex tests. Failure tests usually fall into this category.

Use the leading description for multi-line tests, for example:

\
: multi-name
:
$* 'John' 'Jane' >>EOO
Hello, John!
Hello, Jane!
EOO
\

Here is an example of a description that includes all three components:

\
: multi-name
: Test multiple name arguments
:
: This test makes sure we properly handle multiple names passed as
: separate command line arguments.
:
$* 'John' 'Jane' >>EOO
Hello, John!
Hello, Jane!
EOO
\

Separate multi-line tests with blank lines. You may want to place larger tests
into explicit test scopes for better visual separation (this is especially
helpful if the test contains blank lines, for example, in here-document
fragments). In this case the description should come before the scope. Note
that here-documents are indented as well. For example:

\
: multi-name
:
{
  $* 'John' 'Jane' >>EOO
  Hello, John!

  Hello, Jane!

  EOO
}
\

One-line tests may use the trailing description (which must always be
the test id). Within a test block (one-liners without a blank between
them), the ids should be aligned, for example:

\
$* John >'Hi, John!'       : custom-john
$* World >'Hello, World!'  : custom-world
\

Note that you are free to put multiple spaces between the end of the command
line and the trailing description. But don't try to align ids between blocks
\- this is a maintenance pain.

If multiple tests belong to the same group, consider placing them into an
explicit group scope. A good indication that tests form a group is if their
ids start with the same prefix, as in the above example. If placing tests into
a group scope, use the prefix as the group's id and don't repeat it in the
tests. It is also a good idea to give the summary of the group, for example:

\
: custom
: Test custom greetings
:
{{
  $* John >'Hi, John!'       : john
  $* World >'Hello, World!'  : world
}}
\

In the same vein, don't repeat the testscript id in group or test ids. For
example, if the above tests were in \c{greeting.testscript}, then using
\c{custom-greeting} as the group id would be unnecessarily repetitive since
the id path would then become \c{greeting/custom-greeting/john}, etc.

We quote values that are \i{strings} as opposed to options, file names, paths
(unless they contain spaces), integers, or boolean. When quoting, use single
quotes unless you need expansions (or single quotes) inside. Note that unlike
Bash you do not need to quote variable expansions in order to preserve
whitespaces.  For example:

\
arg = 'Hello   Spaces'
echo $arg              # Hello   Spaces
\

For further reading on testing that we (mostly) agree with, see:

\dl|

\li|\n\n\l{https://blog.nelhage.com/2016/12/how-i-test/ How I Write Tests} by Nelson Elhage\n

  The only part we don't agree on is the (somewhat implied) suggestion to
  write as many tests as possible.||
"
