Automatically run your Elixir project's tests each time you save a file.

Because Test-driven development (TDD) is awesome.

Add it to your dependencies:

For Elixir 1.4 onwards:

# mix.exs
def deps do
  [
    {:mix_test_watch, "~> 1.0", only: [:dev, :test], runtime: false}
  ]
end

For Elixir 1.3 and earlier:

# mix.exs
def deps do
  [
    {:mix_test_watch, "~> 1.0", only: [:dev, :test]}
  ]
end

Optionally, add preferred_cli_env: ["test.watch": :test] for running mix test.watch in :test env by default. It prevents the task from running :dev env config scripts.

# mix.exs
def project do
  [
    ...
    preferred_cli_env: [
      "test.watch": :test
    ],
    ...
  ]
end

Run the mix task:

mix test.watch

Start hacking :)

Through the mix config it is possible to run other mix tasks as well as the test task. For example, if I wished to run the Credo code analysis tool after my tests I would do so like this.

# config/config.exs
use Mix.Config

if Mix.env == :dev do
  config :mix_test_watch,
    tasks: [
      "test",
      "credo",
    ]
end

Tasks are run in the order they appear in the list, and the progression will stop if any command returns a non-zero exit code.

All tasks are run with MIX_ENV set to test.

Any command line arguments passed to the test.watch task will be passed through to the tasks being run. If I only want to run the tests from one file every time I save a file I could do so with this command:

mix test.watch test/file/to_test.exs

Note that if you have configured more than one task to be run these arguments will be passed to all the tasks run, not just the test command.

Elixir 1.3 introduced --stale option that will run only those test files which reference modules that have changed since the last run. You can pass it to test.watch:

mix test.watch --stale

If you want mix test.watch to clear the console before each run, you can enable this option in your config/dev.exs as follows:

# config/config.exs
use Mix.Config

if Mix.env == :dev do
  config :mix_test_watch,
    clear: true
end

To ignore changes from specific files or directories just add exclude: regexp patterns to your config in config/config.exs:

# config/config.exs
use Mix.Config

if Mix.env == :dev do
  config :mix_test_watch,
    exclude: [~r/db_migration\/.*/,
              ~r/useless_.*\.exs/]
end

The default is exclude: [~r/\.#/, ~r{priv/repo/migrations}].

To watch files with extensions other than the default (.erl, .ex, .exs, .eex, .leex, .heex, .xrl, .yrl, .hrl) add them to extra_extensions: in your config:

# config/config.exs
use Mix.Config

if Mix.env == :dev do
  config :mix_test_watch,
    extra_extensions: [".rs"]
end

On Linux you may need to install inotify-tools.

You can enable desktop notifications with ex_unit_notifier.

mix_test_interactive is based on mix test.watch but adds an interactive mode that allows you to dynamically change which tests to run.

mix test.watch

Copyright © 2015 Louis Pilfold

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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