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.

THE RUN HELPER

       Usage: run [OPTIONS] [--] <command...> Options: ! check for non zero exit  code  -N  check
       that  exit  code  is N --separate-stderr split stderr and stdout --keep-empty-lines retain
       empty lines in ${lines[@]}/${stderr_lines[@]}

       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_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.