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bats-file is a helper library providing common filesystem related assertions and helpers for Bats.

Assertions are functions that perform a test and output relevant information on failure to help debugging. They return 1 on failure and 0 otherwise. Output, formatted for readability, is sent to the standard error to make assertions usable outside of @test blocks too.



  • bats-support - output formatting, function call restriction

See the shared documentation to learn how to install and load this library.



Fail if the given file or directory does not exist.

@test 'assert_file_exist()' {
  assert_file_exist /path/to/non-existent-file

On failure, the path is displayed.

-- file does not exist --
path : /path/to/non-existent-file


Fail if the given file or directory exists.

@test 'assert_file_not_exist() {
  assert_file_not_exist /path/to/existing-file

On failure, the path is displayed.

-- file exists, but it was expected to be absent --
path : /path/to/existing-file

Working with temporary directories

When testing code that manipulates the filesystem, it is good practice to run tests in clean, throw-away environments to ensure correctness and reproducibility. Therefore, this library includes convenient functions to create and destroy temporary directories.


Create a temporary directory for the current test in BATS_TMPDIR. The directory is guaranteed to be unique and its name is derived from the test's filename and number for easy identification.


This information is only available in setup, @test and teardown, thus the function must be called from one of these locations.

The path of the directory is displayed on the standard output and is meant to be captured into a variable.

setup() {

For example, for the first test in sample.bats, this snippet creates a directory named sample.bats-1-XXXXXXXXXX, where each trailing X is a random alphanumeric character.

If the directory cannot be created, the function fails and displays an error message on the standard error.

-- ERROR: temp_make --
mktemp: failed to create directory via template ‘/etc/samle.bats-1-XXXXXXXXXX’: Permission denied

Directory name prefix

The directory name can be prefixed with an arbitrary string using the --prefix <prefix> option (-p <prefix> for short).

setup() {
  TEST_TEMP_DIR="$(temp_make --prefix 'myapp-')"

Following the previous example, this will create a directory named myapp-sample.bats-1-XXXXXXXXXX. This can be used to group temporary directories.

Generally speaking, the directory name is of the following form.



Delete a temporary directory, typically created with temp_make.

teardown() {
  temp_del "$TEST_TEMP_DIR"

If the directory cannot be deleted, the function fails and displays an error message on the standard error.

-- ERROR: temp_del --
rm: cannot remove '/etc/samle.bats-1-04RUVmBP7x': No such file or directory

Note: Actually, this function can be used to delete any file or directory. However, it is most useful in deleting temporary directories created with temp_make, hence the naming.

Preserve directory

During development, it is useful to peak into temporary directories post-mortem to see what the tested code has done.

When BATSLIB_TEMP_PRESERVE is set to 1, the function succeeds but the directory is not deleted.

$ BATSLIB_TEMP_PRESERVE=1 bats sample.bats

Preserve directory on failure

During debugging, it is useful to preserve the temporary directories of failing tests.

When BATSLIB_TEMP_PRESERVE_ON_FAILURE is set to 1, the function succeeds but the directory is not deleted if the test has failed.


The outcome of a test is only known in teardown, therefore this feature can be used only when temp_del is called from that location. Otherwise and error is displayed on the standard error.

Transforming displayed paths

Sometimes paths can be long and tiresome to parse to the human eye. To help focus on the interesting bits, all functions support hiding part of the displayed paths by replacing it with an arbitrary string.

A single pattern substitution is performed on the path before displaying it.


The longest match of the pattern BATSLIB_FILE_PATH_REM is replaced with BATSLIB_FILE_PATH_ADD. To anchor the pattern to the beginning or the end, prepend # or %, respectively.

For example, the following example hides the path of the temporary directory where the test takes place.

setup {

@test 'assert_file_exist()' {
  assert_file_exist "${TEST_TEMP_DIR}/path/to/non-existent-file"

teardown() {
  temp_del "$TEST_TEMP_DIR"

On failure, only the relevant part of the path is shown.

-- file does not exist --
path : <temp>/path/to/non-existent-file