Runs the tests for a project.

This task starts the current application, loads up test/test_helper.exs and then requires all files matching the test/**/_test.exs pattern in parallel.

A list of files can be given after the task name in order to select the files to compile:

mix test test/some/particular/file_test.exs

Command line options

• --trace - run tests with detailed reporting; automatically sets --max-cases to 1
• --max-cases - set the maximum number of cases running async
• --cover - the directory to include coverage results
• --force - forces compilation regardless of modification times
• --no-compile - do not compile, even if files require compilation
• --no-start - do not start applications after compilation
• --no-color - disable color in the output
• --color - enable color in the output
• --include - include tests that match the filter
• --exclude - exclude tests that match the filter
• --only - run only tests that match the filter
• --seed - seeds the random number generator used to randomize tests order
• --timeout - set the timeout for the tests

Filters

ExUnit provides tags and filtering functionality that allows developers to select which tests to run. The most common functionality is to exclude some particular tests from running by default in your test helper file:

# Exclude all external tests from running
ExUnit.configure exclude: [external: true]

Then, whenever desired, those tests could be included in the run via the --include flag:

mix test --include external:true

The example above will run all tests that have the external flag set to true. It is also possible to include all examples that have a given tag, regardless of its value:

mix test --include external

Note that all tests are included by default, so unless they are excluded first (either in the test helper or via the --exclude option), the --include flag has no effect.

For this reason, Mix also provides an --only option that excludes all tests and includes only the given ones:

mix test --only external

Which is equivalent to:

mix test --include external --exclude test

In case a single file is being tested, it is possible pass a specific line number:

mix test test/some/particular/file_test.exs:12

Which is equivalent to:

mix test --only line:12 test/some/particular/file_test.exs

Configuration

• :test_paths - list of paths containing test files, defaults to ["test"]. It is expected all test paths to contain a test_helper.exs file.

• :test_pattern - a pattern to load test files, defaults to *_test.exs.

• :test_coverage - a set of options to be passed down to the coverage mechanism.

Coverage

The :test_coverage configuration accepts the following options:

• :output - the output for cover results, defaults to "cover"
• :tool - the coverage tool

By default, a very simple wrapper around OTP’s cover is used as a tool, but it can be overridden as follows:

test_coverage: [tool: CoverModule]

CoverModule can be any module that exports start/2, receiving the compilation path and the test_coverage options as arguments. It must return an anonymous function of zero arity that will be run after the test suite is done or nil.