Ubuntu Manpage: bats - Bats test file format

NAME

       bats - Bats test file format

DESCRIPTION

       A  Bats test file is a Bash script with special syntax for defining test cases. Under the hood, each test
       case is just a function with a description.

           #!/usr/bin/env bats

           @test "addition using bc" {
             result="$(echo 2+2 | bc)"
             [ "$result" -eq 4 ]
           }

           @test "addition using dc" {
             result="$(echo 2 2+p | dc)"
             [ "$result" -eq 4 ]
           }

       Each Bats test file is evaluated n+1 times, where n is the number of test cases in the  file.  The  first
       run  counts  the number of test cases, then iterates over the test cases and executes each one in its own
       process.

Tagging tests

Each test has a list of tags attached to it. Without specification, this list is empty. Tags can be
defined in two ways. The first being # bats test_tags=:

# bats test_tags=tag:1, tag:2, tag:3 @test "second test" { # ... }

@test "second test" { # ... }

These tags (tag:1, tag:2, tag:3) will be attached to the test first test. The second test will have no
tags attached. Values defined in the # bats test_tags= directive will be assigned to the next @test that
is being encountered in the file and forgotten after that. Only the value of the last # bats test_tags=
directive before a given test will be used.

Sometimes, we want to give all tests in a file a set of the same tags. This can be achieved via # bats
file_tags=. They will be added to all tests in the file after that directive. An additional # bats
file_tags= directive will override the previously defined values:

@test "Zeroth test" {
# will have no tags
}

# bats file_tags=a:b
# bats test_tags=c:d

@test "First test" {
# will be tagged a:b, c:d
}

# bats file_tags=

@test "Second test" {
# will have no tags
}

Tags are case sensitive and must only consist of alphanumeric characters and _, -, or :. They must not
contain whitespaces! The colon is intended as a separator for (recursive) namespacing.

Tag lists must be separated by commas and are allowed to contain whitespace. They must not contain empty
tags like test_tags=,b (first tag is empty), test_tags=a,,c, test_tags=a, ,c (second tag is only
whitespace/empty), test_tags=a,b, (third tag is empty).

Every tag starting with bats: (case insensitive!) is reserved for Bats´ internal use:

bats:focus
If any test with the tag bats:focus is encountered in a test suite, only those tagged with this
tag will be executed. To prevent the CI from silently running on a subset of tests due to an
accidentally commited bats:focus tag, the exit code of successful runs will be overriden to 1.

Should you require the true exit code, e.g. for a git bisect operation, you can disable this
behavior by setting BATS_NO_FAIL_FOCUS_RUN=1 when running bats, but make sure to not commit this
to CI!

THE RUN HELPER

       Usage: run [OPTIONS] [--]

       Many  Bats  tests  need  to run a command and then make assertions about its exit status and output. Bats
       includes a run helper that invokes its arguments as a command, saves the  exit  status  and  output  into
       special  global  variables,  and  (optionally)  checks  exit  status  against  a given expected value. If
       successful, run returns with a 0 status code so you can continue to make assertions in your test case.

       For example, let´s say you´re testing that the foo command, when passed  a  nonexistent  filename,  exits
       with a 1 status code and prints an error message.

           @test "invoking foo with a nonexistent file prints an error" {
             run -1 foo nonexistent_filename
             [ "$output" = "foo: no such file ´nonexistent_filename´" ]
           }

       The  -1  as first argument tells run to expect 1 as an exit status, and to fail if the command exits with
       any other value. On failure, both actual and expected values will be displayed, along  with  the  invoked
       command and its output:

           (in test file test.bats, line 2)
            `run -1 foo nonexistent_filename´ failed, expected exit code 1, got 127

       This error indicates a possible problem with the installation or configuration of foo; note that a simple
       [ $status != 0 ] test would not have caught this kind of failure.

       The $status variable contains the status code of the command,  and  the  $output  variable  contains  the
       combined contents of the command´s standard output and standard error streams.

       A third special variable, the $lines array, is available for easily accessing individual lines of output.
       For example, if you want to test that invoking foo without any arguments prints usage information on  the
       first line:

           @test "invoking foo without arguments prints usage" {
             run -1 foo
             [ "${lines[0]}" = "usage: foo <filename>" ]
           }

       By default run leaves out empty lines in ${lines[@]}. Use run --keep-empty-lines to retain them.

       Additionally,  you  can  use  --separate-stderr  to  split  stdout  and  stderr  into $output/$stderr and
       ${lines[@]}/${stderr_lines[@]}.

       All additional parameters to run should come before the command. If you want to run a command that starts
       with -, prefix it with -- to prevent run from parsing it as an option.

THE LOAD COMMAND

       You may want to share common code across multiple test files. Bats includes a convenient load command for
       sourcing a Bash source file relative to the location of the current test file. For example, if you have a
       Bats test in test/foo.bats, the command

           load test_helper

       will  source the script test/test_helper.bash in your test file. This can be useful for sharing functions
       to set up your environment or load fixtures.

THE BATS_LOAD_LIBRARY COMMAND

Some libraries are installed on the system, e.g. by npm or brew. These should not be loaded, as their
path depends on the installation method. Instead, one should use bats_load_library together with setting
BATS_LIB_PATH, a PATH-like colon-delimited variable.

bats_load_library has two modes of resolving requests:

1. by relative path from the BATS_LIB_PATH to a file in the library

2. by library name, expecting libraries to have a load.bash entrypoint

For example if your BATS_LIB_PATH is set to ~/.bats/libs:/usr/lib/bats, then bats_load_library
test_helper would look for existing files with the following paths:

○ ~/.bats/libs/test_helper

○ ~/.bats/libs/test_helper/load.bash

○ /usr/lib/bats/test_helper

○ /usr/lib/bats/test_helper/load.bash

The first existing file in this list will be sourced.

If you want to load only part of a library or the entry point is not named load.bash, you have to include
it in the argument: bats_load_library library_name/file_to_load will try

○ ~/.bats/libs/library_name/file_to_load

○ ~/.bats/libs/library_name/file_to_load/load.bash

○ /usr/lib/bats/library_name/file_to_load

○ /usr/lib/bats/library_name/file_to_load/load.bash

Apart from the changed lookup rules, bats_load_library behaves like load.

Note: As seen above load.bash is the entry point for libraries and meant to load more files from its
directory or other libraries.

Note: Obviously, the actual BATS_LIB_PATH is highly dependent on the environment. To maintain a uniform
location across systems, (distribution) package maintainers are encouraged to use /usr/lib/bats/ as the
install path for libraries where possible. However, if the package manager has another preferred
location, like npm or brew, you should use this instead.

THE SKIP COMMAND

       Tests can be skipped by using the skip command at the point in a test you wish to skip.

           @test "A test I don´t want to execute for now" {
             skip
             run -0 foo
           }

       Optionally, you may include a reason for skipping:

           @test "A test I don´t want to execute for now" {
             skip "This command will return zero soon, but not now"
             run -0 foo
           }

       Or you can skip conditionally:

           @test "A test which should run" {
             if [ foo != bar ]; then
               skip "foo isn´t bar"
             fi

             run -0 foo
           }

THE BATS_REQUIRE_MINIMUM_VERSION COMMAND

       Code for newer versions of Bats can be incompatible with older versions. In the best case this will  lead
       to  an  error  message  and  a  failed  test  suite.  In the worst case, the tests will pass erroneously,
       potentially masking a failure.

       Use bats_require_minimum_version <Bats version number> to  avoid  this.  It  communicates  in  a  concise
       manner, that you intend the following code to be run under the given Bats version or higher.

       Additionally,  this function will communicate the current Bats version floor to subsequent code, allowing
       e.g. Bats´ internal warning to give more informed warnings.

       Note: By default,  calling  bats_require_minimum_version  with  versions  before  Bats  1.7.0  will  fail
       regardless  of  the  required  version  as  the  function  is  not  available.  However,  you can use the
       bats-backports plugin (https://github.com/bats-core/bats-backports) to make your code usable  with  older
       versions, e.g. during migration while your CI system is not yet upgraded.

SETUP AND TEARDOWN FUNCTIONS

       You  can  define  special  setup  and  teardown  functions  which  run  before  and after each test case,
       respectively. Use these to load fixtures, set up your environment, and clean up when you´re done.

CODE OUTSIDE OF TEST CASES

       You can include code in your test file outside of @test functions. For example, this may be useful if you
       want  to check for dependencies and fail immediately if they´re not present. However, any output that you
       print in code outside of @test,  setup  or  teardown  functions  must  be  redirected  to  stderr  (>&2).
       Otherwise, the output may cause Bats to fail by polluting the TAP stream on stdout.

SPECIAL VARIABLES

There are several global variables you can use to introspect on Bats tests:

○ $BATS_TEST_FILENAME is the fully expanded path to the Bats test file.

○ $BATS_TEST_DIRNAME is the directory in which the Bats test file is located.

○ $BATS_TEST_NAMES is an array of function names for each test case.

○ $BATS_TEST_NAME is the name of the function containing the current test case.

○ BATS_TEST_NAME_PREFIX will be prepended to the description of each test on stdout and in reports.

○ $BATS_TEST_DESCRIPTION is the description of the current test case.

○ BATS_TEST_RETRIES is the maximum number of additional attempts that will be made on a failed test
before it is finally considered failed. The default of 0 means the test must pass on the first
attempt.

○ BATS_TEST_TIMEOUT is the number of seconds after which a test (including setup) will be aborted and
marked as failed. Updates to this value in setup() or @test cannot change the running timeout
countdown, so the latest useful update location is setup_file().

○ $BATS_TEST_NUMBER is the (1-based) index of the current test case in the test file.

○ $BATS_SUITE_TEST_NUMBER is the (1-based) index of the current test case in the test suite (over all
files).

○ $BATS_TMPDIR is the base temporary directory used by bats to create its temporary files /
directories. (default: $TMPDIR. If $TMPDIR is not set, /tmp is used.)

○ $BATS_RUN_TMPDIR is the location to the temporary directory used by bats to store all its internal
temporary files during the tests. (default: $BATS_TMPDIR/bats-run-$BATS_ROOT_PID-XXXXXX)

○ $BATS_FILE_EXTENSION (default: bats) specifies the extension of test files that should be found when
running a suite (via bats [-r] suite_folder/)

○ $BATS_SUITE_TMPDIR is a temporary directory common to all tests of a suite. Could be used to create
files required by multiple tests.

○ $BATS_FILE_TMPDIR is a temporary directory common to all tests of a test file. Could be used to
create files required by multiple tests in the same test file.

○ $BATS_TEST_TMPDIR is a temporary directory unique for each test. Could be used to create files
required only for specific tests.

○ $BATS_VERSION is the version of Bats running the test.