Bats is a TAP-compliant testing framework for Bash. It provides a simple way to verify that the UNIX programs you write behave as expected.
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 ]
}
Bats is most useful when testing software written in Bash, but you can use it to test any UNIX program.
Test cases consist of standard shell commands. Bats makes use of
Bash's errexit
(set -e
) option when running test cases. If every
command in the test case exits with a 0
status code (success), the
test passes. In this way, each line is an assertion of truth.
To run your tests, invoke the bats
interpreter with a path to a test
file. The file's test cases are run sequentially and in isolation. If
all the test cases pass, bats
exits with a 0
status code. If there
are any failures, bats
exits with a 1
status code.
When you run Bats from a terminal, you'll see output as each test is performed, with a check-mark next to the test's name if it passes or an "X" if it fails.
$ bats addition.bats
✓ addition using bc
✓ addition using dc
2 tests, 0 failures
If Bats is not connected to a terminal—in other words, if you
run it from a continuous integration system or redirect its output to
a file—the results are displayed in human-readable, machine-parsable
TAP format.
You can force TAP output from a terminal by invoking Bats with the
--tap
option.
$ bats --tap addition.bats
1..2
ok 1 addition using bc
ok 2 addition using dc
You can invoke the bats
interpreter with multiple test file
arguments, or with a path to a directory containing multiple .bats
files. Bats will run each test file individually and aggregate the
results. If any test case fails, bats
exits with a 1
status code.
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.
For details about exactly how Bats evaluates test files, see Bats Evaluation Process on the wiki.
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 then 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 foo nonexistent_filename
[ "$status" -eq 1 ]
[ "$output" = "foo: no such file 'nonexistent_filename'" ]
}
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 $lines
array, is available for easily
accessing individual lines of output. For example, if you want to test
that invoking foo
without any arguments prints usage information on
the first line:
@test "invoking foo without arguments prints usage" {
run foo
[ "$status" -eq 1 ]
[ "${lines[0]}" = "usage: foo <filename>" ]
}
You may want to share common code across multiple test files. Bats
includes a convenient load
command for sourcing a Bash source file
relative to the location of the current test file. For example, if you
have a Bats test in test/foo.bats
, the command
load test_helper
will source the script test/test_helper.bash
in your test file. This
can be useful for sharing functions to set up your environment or load
fixtures.
Tests can be skipped by using the skip
command at the point in a
test you wish to skip.
@test "A test I don't want to execute for now" {
skip
run foo
[ "$status" -eq 0 ]
}
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 foo
[ "$status" -eq 0 ]
}
Or you can skip conditionally:
@test "A test which should run" {
if [ foo != bar ]; then
skip "foo isn't bar"
fi
run foo
[ "$status" -eq 0 ]
}
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.
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
.
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_TMPDIR
is the location to a directory that may be used to store temporary files.
Check out a copy of the Bats repository. Then, either add the Bats
bin
directory to your $PATH
, or run the provided install.sh
command with the location to the prefix in which you want to install
Bats. For example, to install Bats into /usr/local
,
$ git clone https://github.com/sstephenson/bats.git
$ cd bats
$ ./install.sh /usr/local
Note that you may need to run install.sh
with sudo
if you do not
have permission to write to the installation prefix.
The Bats source code repository is hosted on GitHub. There you can file bugs on the issue tracker or submit tested pull requests for review.
For real-world examples from open-source projects using Bats, see Projects Using Bats on the wiki.
To learn how to set up your editor for Bats syntax highlighting, see Syntax Highlighting on the wiki.
0.3.1 (October 28, 2013)
- Fixed an incompatibility with the pretty formatter in certain environments such as tmux.
- Fixed a bug where the pretty formatter would crash if the first line of a test file's output was invalid TAP.
0.3.0 (October 21, 2013)
- Improved formatting for tests run from a terminal. Failing tests
are now colored in red, and the total number of failing tests is
displayed at the end of the test run. When Bats is not connected to
a terminal (e.g. in CI runs), or when invoked with the
--tap
flag, output is displayed in standard TAP format. - Added the ability to skip tests using the
skip
command. - Added a message to failing test case output indicating the file and line number of the statement that caused the test to fail.
- Added "ad-hoc" test suite support. You can now invoke
bats
with multiple filename or directory arguments to run all the specified tests in aggregate. - Added support for test files with Windows line endings.
- Fixed regular expression warnings from certain versions of Bash.
- Fixed a bug running tests containing lines that begin with
-e
.
0.2.0 (November 16, 2012)
- Added test suite support. The
bats
command accepts a directory name containing multiple test files to be run in aggregate. - Added the ability to count the number of test cases in a file or
suite by passing the
-c
flag tobats
. - Preprocessed sources are cached between test case runs in the same file for better performance.
0.1.0 (December 30, 2011)
- Initial public release.
© 2013 Sam Stephenson. Bats is released under an MIT-style license;
see LICENSE
for details.