Minitest uses Ruby classes, if a Minitest class inherits from another class, it will also inherit its methods causing Minitest to run the parent's tests twice. In some cases, we want them to run them twice, but most of the time, we don't.

Ruby Minitest Analyzer will analyze your Minitest classes and detect any duplicate test run.

This Library is explained in detail in this Post

See the following case.

require "minitest"
require "minitest/autorun"

class ProductParentTest < Minitest::Test
  def test_parent
    puts __method__
  end
end

class ProductTest < ProductParentTest
  def test_1
    puts __method__
  end

  def test_2
    puts __method__
  end
end

How many tests will we run if we run the ProductTest tests? 4! (yes, four). Try it!

# Running:

test_2
test_parent
test_1
test_parent

Finished in 0.001218s, 3284.0724 runs/s, 0.0000 assertions/s.
4 runs, 0 assertions, 0 failures, 0 errors, 0 skips

The reason is that ProductTest is a subclass of ProductParentTest.

Note: I added a new cop to Rubocop that checks for duplicated run tests. The cop has some limitations that this library solves. For example, in the cop, the classes should be in the same file.

More details in this Post

Other scenarios were it doesn't create duplicated tests:

class A < Minitest
  test xyz do 
  end

  class B < Minitest
    test bar do 
    end
  end

  class C < Minitest
    test foo do 
    end
  end
end

Add this line to your Application's Gemfile:

gem 'ruby_minitest_analyzer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ruby_minitest_analyzer

1. Create a new test minitest_analyzer.rb file.
2. Create a method require_all_test_files requiring all the tests files, including the files needed to run the tests e.g. test_helper.rb. See the example below.
3. Call ::RubyMinitestAnalyzer.run!(nil).
4. Run the file.

# I placed this file within /test
  
require_relative 'test_helper.rb'
require 'ruby_minitest_analyzer' 

def require_all_files
  # require test_helpers
  require_relative("test_helper")

  # require tests classes
  Dir[File.expand_path('**/*.rb', __dir__)].each do |f|
    require_relative(f)
  end
end

require_all_files
::RubyMinitestAnalyzer.run!(nil)

Running the file example:

➜  rails-minitest-analyzer git:(main) ✗ ruby minitest.rb 
---------------Setting up---------------
Requiring files...
Total of 6 test classes to analyze. 
---------------Setup finished! Ready to analyze the tests---------------
Analyzing!

Analyzed a total of 6 classes.
      
* Total duplicated tests that can be removed: 12
* Total classes with duplicated tests: 3 
      
Classes that run the tests multiple times: 

CLASS NAME      | CLASS_TEST_METHODS_COUNT | CLASS_DESCENDANT_COUNT | EXTRA_TESTS_EXECUTIONS_COUNT 
----------------|--------------------------|------------------------|------------------------------
GrandParentTest | 1                        | 5                      | 5                            
Parent1Test     | 2                        | 2                      | 4                            
Parent2Test     | 3                        | 1                      | 3                            

Finished!  

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/ruby_minitest_analyzer.

The gem is available as open source under the terms of the MIT License.