ExUnit — ExUnit v1.16.3

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# View Source ExUnit (ExUnit v1.16.3)

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) Note that 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. Run `mix help 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

test_id()

## Functions

after_suite(function)

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

async_run()

Starts tests asynchronously while test cases are still loading.

await_run(task)

Awaits for a test suite that has been started with `async_run/0`.

configuration()

Returns ExUnit configuration.

configure(options)

Configures ExUnit.

fetch_test_supervisor()

Fetches the test supervisor for the current test.

plural_rule(word)

Returns the pluralization for `word`.

plural_rule(word, pluralization)

Registers a `pluralization` for `word`.

run(additional_modules \\ [])

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

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# failed()

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

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

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# state()

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

All tests start with a state of `nil`.

A finished test can be in one of five states:

1. Passed (also represented by `nil`)
2. Failed
3. Skipped (via @tag :skip)
4. Excluded (via :exclude filters)
5. Invalid (when setup_all fails)

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# suite_result()

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    @type 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

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# test_id()

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    @type test_id() :: {module(), name :: atom()}

# Functions

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# after_suite(function)

View Source (since 1.8.0)

    @spec 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.

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# async_run()

View Source (since 1.12.0)

    @spec async_run() :: Task.t()

Starts tests asynchronously while test cases are still loading.

It returns a task that must be given to `await_run/0` when a result is desired.

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# await_run(task)

View Source (since 1.12.0)

    @spec await_run(Task.t()) :: suite_result()

Awaits for a test suite that has been started with `async_run/0`.

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# configuration()

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    @spec configuration() :: Keyword.t()

Returns ExUnit configuration.

For the available configuration options, see `configure/1`.

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# configure(options)

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    @spec 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`. This can also be configured to a specific level with `capture_log: [level: LEVEL]`, for example: `capture_log: [level: :emergency]` to prevent any output from test failures. 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`;

  - `:success` - success message (defaults to `:green`)

  - `:invalid` - invalid test message (defaults to `:yellow`)

  - `:skipped` - skipped test message (defaults to `:yellow`)

  - `:failure` - failed test message (defaults to `:red`)

  - `:error_info` - display of actual error (defaults to `:red`)

  - `:extra_info` - additional information (defaults to `:cyan`)

  - `:location_info` - filename and tags (defaults to `[:bright, :black]`)

  - `: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 deletions 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. See the "Filters" section in the documentation for `ExUnit.Case`;

- `:exit_status` - specifies an alternate exit status to use when the test suite fails. Defaults to 2;

- `: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 and filters);

- `: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. This is typically used by Mix to filter which tests should run;

- `:rand_algorithm` - algorithm to be used when generating the test seed. Available algorithms can be found in Erlang's `:rand` documentation (see `:rand.builting_arg/0`). Available since v1.16.0. Before v1.16.0, the algorithm was hard-coded to `:exs1024`. On Elixir v1.16.0 and after, the default changed to `:exsss`;

- `: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. A `:seed` of `0` will disable randomization and the tests in each file will always run in the order that they were defined in;

- `: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.

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# fetch_test_supervisor()

View Source (since 1.11.0)

    @spec fetch_test_supervisor() :: {:ok, pid()} | :error

Fetches the test supervisor for the current test.

Returns `{:ok, supervisor_pid}` or `:error` if not called from the test process.

This is the same supervisor as used by `ExUnit.Callbacks.start_supervised/2` and similar, see `ExUnit.Callbacks` module documentation for more information.

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# plural_rule(word)

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    @spec plural_rule(binary()) :: binary()

Returns the pluralization for `word`.

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

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# plural_rule(word, pluralization)

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    @spec plural_rule(binary(), binary()) :: :ok

Registers a `pluralization` for `word`.

If one is already registered, it is replaced.

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# run(additional_modules \\ [])

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    @spec run([module()]) :: suite_result()

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

From Elixir v1.14, it accepts an optional list of modules to run as part of the suite. This is often used to rerun modules already loaded in memory.

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

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# start(options \\ [])

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    @spec 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.