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 emtpy 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 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
}

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_DESCRIPTION is the description of the current test case.
$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.