ExUnit

Unit testing framework for Elixir.

Example

A basic setup for ExUnit is shown below:

# File: assertion_test.exs

# 1) Start ExUnit.
ExUnit.start()

# 2) Create a new test module (test case) and use "ExUnit.Case".
defmodule AssertionTest do
  # 3) Notice we pass "async: true", this runs the test case
  #    concurrently with other test cases. The individual tests
  #    within each test case are still run serially.
  use ExUnit.Case, async: true

  # 4) Use the "test" macro instead of "def" for clarity.
  test "the truth" do
    assert true
  end
end

To run the tests above, run the file using elixir from the command line. Assuming you named the file assertion_test.exs, you can run it as:

elixir assertion_test.exs

Case, Callbacks and Assertions

See ExUnit.Case and ExUnit.Callbacks for more information about defining test cases and setting up callbacks.

The ExUnit.Assertions module contains a set of macros to generate assertions with appropriate error messages.

Integration with Mix

Mix is the project management and build tool for Elixir. Invoking mix test from the command line will run the tests in each file matching the pattern *_test.exs found in the test directory of your project.

You must create a test_helper.exs file inside the test directory and put the code common to all tests there.

The minimum example of a test_helper.exs file would be:

# test/test_helper.exs
ExUnit.start()

Mix will load the test_helper.exs file before executing the tests. It is not necessary to require the test_helper.exs file in your test files. See Mix.Tasks.Test for more information.

Summary

Types

failed(): The error state returned by ExUnit.Test and ExUnit.TestModule
state(): All tests start with a state of nil.
suite_result(): A map representing the results of running a test suite

Functions

after_suite(function): Sets a callback to be executed after the completion of a test suite.
configuration(): Returns ExUnit configuration.
configure(options): Configures ExUnit.
plural_rule(word): Returns the pluralization for word.
plural_rule(word, pluralization): Registers a pluralization for word.
run(): Runs the tests. It is invoked automatically if ExUnit is started via start/1.
start(options \\ []): Starts ExUnit and automatically runs tests right before the VM terminates.

Types

failed()

Specs

failed() :: [{Exception.kind(), reason :: term(), Exception.stacktrace()}]

The error state returned by ExUnit.Test and ExUnit.TestModule

state()

Specs

state() ::
  nil
  | {:failed, failed()}
  | {:skipped, binary()}
  | {:excluded, binary()}
  | {:invalid, module()}

All tests start with a state of nil.

A finished test can be in one of five states:

Passed (also represented by nil)
Failed
Skipped (via @tag :skip)
Excluded (via :exclude filters)
Invalid (when setup_all fails)

suite_result()

Specs

suite_result() :: %{
  excluded: non_neg_integer(),
  failures: non_neg_integer(),
  skipped: non_neg_integer(),
  total: non_neg_integer()
}

A map representing the results of running a test suite

Functions

after_suite(function)

Specs

after_suite((suite_result() -> any())) :: :ok

Sets a callback to be executed after the completion of a test suite.

Callbacks set with after_suite/1 must accept a single argument, which is a map containing the results of the test suite's execution.

If after_suite/1 is called multiple times, the callbacks will be called in reverse order. In other words, the last callback set will be the first to be called.

configuration()

Specs

configuration() :: Keyword.t()

Returns ExUnit configuration.

configure(options)

Specs

configure(Keyword.t()) :: :ok

Configures ExUnit.

Options

ExUnit supports the following options:

:assert_receive_timeout - the timeout to be used on assert_receive calls in milliseconds, defaults to 100;
:autorun - if ExUnit should run by default on exit. Defaults to true;
:capture_log - if ExUnit should default to keeping track of log messages and print them on test failure. Can be overridden for individual tests via @tag capture_log: false. Defaults to false;
:colors - a keyword list of color options to be used by some formatters:
- :enabled - boolean option to enable colors, defaults to IO.ANSI.enabled?/0;
- :diff_insert - color of the insertions on diffs, defaults to :green;
- :diff_insert_whitespace - color of the whitespace insertions on diffs, defaults to IO.ANSI.color_background(2, 0, 0);
- :diff_delete - color of the deletiopns on diffs, defaults to :red;
- :diff_delete_whitespace - color of the whitespace deletions on diffs, defaults to IO.ANSI.color_background(0, 2, 0);
:exclude - specifies which tests are run by skipping tests that match the filter;
:failures_manifest_file - specifies a path to the file used to store failures between runs;
:formatters - the formatters that will print results, defaults to [ExUnit.CLIFormatter];
:include - specifies which tests are run by skipping tests that do not match the filter. Keep in mind that all tests are included by default, so unless they are excluded first, the :include option has no effect. To only run the tests that match the :include filter, exclude the :test tag first (see the documentation for ExUnit.Case for more information on tags);
:max_cases - maximum number of tests to run in parallel. Only tests from different modules run in parallel. It defaults to System.schedulers_online * 2 to optimize both CPU-bound and IO-bound tests;
:max_failures - the suite stops evaluating tests when this number of test failures is reached. All tests within a module that fail when using the setup_all/1,2 callbacks are counted as failures. Defaults to :infinity;
:only_test_ids - a list of {module_name, test_name} tuples that limits what tests get run;
:refute_receive_timeout - the timeout to be used on refute_receive calls in milliseconds, defaults to 100;
:seed - an integer seed value to randomize the test suite. This seed is also mixed with the test module and name to create a new unique seed on every test, which is automatically fed into the :rand module. This provides randomness between tests, but predictable and reproducible results;
:slowest - prints timing information for the N slowest tests. Running ExUnit with slow test reporting automatically runs in trace mode. It is disabled by default;
:stacktrace_depth - configures the stacktrace depth to be used on formatting and reporters, defaults to 20;
:timeout - sets the timeout for the tests in milliseconds, defaults to 60_000;
:trace - sets ExUnit into trace mode, this sets :max_cases to 1 and prints each test case and test while running. Note that in trace mode test timeouts will be ignored as timeout is set to :infinity.
:test_location_relative_path - the test location is the file:line information printed by tests as a shortcut to run a given test. When this value is set, the value is used as a prefix for the test itself. This is typically used by Mix to properly set-up umbrella projects

Any arbitrary configuration can also be passed to configure/1 or start/1, and these options can then be used in places such as custom formatters. These other options will be ignored by ExUnit itself.

plural_rule(word)

Specs

plural_rule(binary()) :: binary()

Returns the pluralization for word.

If one is not registered, returns the word appended with an "s".

plural_rule(word, pluralization)

Specs

plural_rule(binary(), binary()) :: :ok

Registers a pluralization for word.

If one is already registered, it is replaced.

run()

Specs

run() :: suite_result()

Runs the tests. It is invoked automatically if ExUnit is started via start/1.

Returns a map containing the total number of tests, the number of failures, the number of excluded tests and the number of skipped tests.

start(options \\ [])

Specs

start(Keyword.t()) :: :ok

Starts ExUnit and automatically runs tests right before the VM terminates.

It accepts a set of options to configure ExUnit (the same ones accepted by configure/1).

If you want to run tests manually, you can set the :autorun option to false and use run/0 to run tests.