Supporting library for Bats test helpers
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README.md

Important: bats-core has been renamed to bats-support. GitHub automatically redirects all references, e.g. submodules and clones will continue to work, but you are encouraged to update them. Version numbering continues where bats-core left off.


bats-support

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bats-support is a supporting library providing common functions to test helper libraries written for Bats.

Features:

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

If you want to use this library in your own helpers or just want to learn about its internals see the developer documentation in the source files.

Error reporting

fail

Display an error message and fail. This function provides a convenient way to report failure in arbitrary situations. You can use it to implement your own helpers when the ones available do not meet your needs. Other functions use it internally as well.

@test 'fail()' {
  fail 'this test always fails'
}

The message can also be specified on the standard input.

@test 'fail() with pipe' {
  echo 'this test always fails' | fail
}

This function always fails and simply outputs the given message.

this test always fails

Output formatting

Many test helpers need to produce human readable output. This library provides a simple way to format simple messages and key value pairs, and display them on the standard error.

Simple message

Simple messages without structure, e.g. one-line error messages, are simply wrapped in a header and a footer to help them stand out.

-- ERROR: assert_output --
`--partial' and `--regexp' are mutually exclusive
--

Key-Value pairs

Some helpers, e.g. assertions, structure output as key-value pairs. This library provides two ways to format them.

When the value is one line long, a pair can be displayed in a columnar fashion called two-column format.

-- output differs --
expected : want
actual   : have
--

When the value is longer than one line, the key and value must be displayed on separate lines. First, the key is displayed along with the number of lines in the value. Then, the value, indented by two spaces for added readability, starting on the next line. This is called multi-line format.

-- command failed --
status : 1
output (2 lines):
  Error! Something went terribly wrong!
  Our engineers are panicing... \`>`;/
--

Sometimes, for clarity, it is a good idea to display related values also in this format, even if they are just one line long.

-- output differs --
expected (1 lines):
  want
actual (3 lines):
  have 1
  have 2
  have 3
--

Language and Execution

Restricting invocation to specific locations

Sometimes a helper may work properly only when called from a certain location. Because it depends on variables to be set or some other side effect.

A good example is cleaning up temporary files only if the test has succeeded. The outcome of a test is only available in teardown. Thus, to avoid programming mistakes, it makes sense to restrict such a clean-up helper to that function.

batslib_is_caller checks the call stack and returns 0 if the caller was invoked from a given function, and 1 otherwise. This function becomes really useful with the --indirect option, which allows calls through intermediate functions, e.g. the calling function may be called from a function that was called from the given function.

Staying with the example above, the following code snippet implements a helper that is restricted to teardown or any function called indirectly from it.

clean_up() {
  # Check caller.
  if batslib_is_caller --indirect 'teardown'; then
    echo "Must be called from \`teardown'" \
      | batslib_decorate 'ERROR: clean_up' \
      | fail
    return $?
  fi

  # Body goes here...
}

In some cases a helper may be called from multiple locations. For example, a logging function that uses the test name, description or number, information only available in setup, @test or teardown, to distinguish entries. The following snippet implements this restriction.

log_test() {
  # Check caller.
  if ! ( batslib_is_caller --indirect 'setup' \
      || batslib_is_caller --indirect "$BATS_TEST_NAME" \
      || batslib_is_caller --indirect 'teardown' )
  then
    echo "Must be called from \`setup', \`@test' or \`teardown'" \
      | batslib_decorate 'ERROR: log_test' \
      | fail
    return $?
  fi

  # Body goes here...
}