RuboCop Minitest

A RuboCop extension focused on enforcing Minitest best practices and coding conventions. The library is based on the guidelines outlined in the community Minitest Style Guide.

Installation

Just install the rubocop-minitest gem

$ gem install rubocop-minitest

or if you use bundler put this in your Gemfile

gem 'rubocop-minitest', require: false

Usage

You need to tell RuboCop to load the Minitest extension. There are three ways to do this:

RuboCop configuration file

Put this into your .rubocop.yml.

plugins: rubocop-minitest

Alternatively, use the following array notation when specifying multiple extensions.

plugins:
  - rubocop-other-extension
  - rubocop-minitest

Now you can run rubocop and it will automatically load the RuboCop Minitest cops together with the standard cops.

[!NOTE] The plugin system is supported in RuboCop 1.72+. In earlier versions, use require instead of plugins.

Command line

$ rubocop --plugin rubocop-minitest

Rake task

require 'rubocop/rake_task'

RuboCop::RakeTask.new do |task|
  task.plugins << 'rubocop-minitest'
end

The Cops

All cops are located under lib/rubocop/cop/minitest, and contain examples/documentation. The documentation is published here.

In your .rubocop.yml, you may treat the Minitest cops just like any other cop. For example:

Minitest/AssertNil:
  Exclude:
    - test/my_file_to_ignore_test.rb

Testing your own cops

This gem provides RuboCop::TestCase, a base test case class for testing custom cops with Minitest. Require rubocop/minitest/support in your test helper, then inherit from RuboCop::TestCase to get the assert_offense, assert_correction, assert_no_corrections, and assert_no_offenses assertions:

require 'rubocop/minitest/support'

module CustomCops
  class MyCopTest < RuboCop::TestCase
    def test_registers_offense
      assert_offense(<<~RUBY)
        bad_method
        ^^^^^^^^^^ Use `good_method` instead of `bad_method`.
      RUBY

      assert_correction(<<~RUBY)
        good_method
      RUBY
    end

    def test_does_not_register_offense
      assert_no_offenses(<<~RUBY)
        good_method
      RUBY
    end
  end
end

The cop under test is derived from the test class name: CustomCops::MyCopTest resolves CustomCops::MyCop, then RuboCop::Cop::Minitest::MyCop. Define a cop_class method in the test class to specify the cop explicitly:

class MyCopTest < RuboCop::TestCase
  private

  def cop_class
    CustomCops::MyCop
  end
end

The configuration for the cop under test and the target Ruby version can be specified by overriding cop_config, other_cops, or target_ruby_version in the test class:

class MyCopTest < RuboCop::TestCase
  private

  def cop_config
    { 'Max' => 1 }
  end

  def target_ruby_version
    3.0
  end
end

To change them for a single test, assign them in the test method. This makes it possible for tests targeting different Ruby versions to live in the same test class:

class MyCopTest < RuboCop::TestCase
  def test_registers_offense_on_ruby31
    self.target_ruby_version = 3.1

    assert_offense(<<~RUBY)
      bad_method
      ^^^^^^^^^^ Use `good_method` instead of `bad_method`.
    RUBY
  end

  def test_does_not_register_offense_on_ruby30
    self.target_ruby_version = 3.0

    assert_no_offenses(<<~RUBY)
      bad_method
    RUBY
  end
end

The default configuration of extensions registered as lint_roller plugins is applied automatically. For other extensions, call RuboCop::ConfigLoader.inject_defaults!('path/to/default.yml') in your test helper.

Documentation

You can read a lot more about RuboCop Minitest in its official docs.

Readme Badge

If you use RuboCop Minitest in your project, you can include one of these badges in your readme to let people know that your code is written following the community Minitest Style Guide.

Here are the Markdown snippets for the two badges:

[![Minitest Style Guide](https://img.shields.io/badge/code_style-rubocop-brightgreen.svg)](https://github.com/rubocop/rubocop-minitest)

[![Minitest Style Guide](https://img.shields.io/badge/code_style-community-brightgreen.svg)](https://minitest.rubystyle.guide)

Contributing

Checkout the contribution guidelines.

License

rubocop-minitest is MIT licensed. See the accompanying file for the full text.