Two ways of testing modules with Minitest

include_module.rb

class TestMyModule < Minitest::Test
  include MyModule
  
  def test_method_from_my_module
    actual = method_from_my_module input_data
    
    assert_equal 'something', actual
  end
end

test_only_class.rb

class TestMyModule < Minitest::Test
  
  class TestClass
    include MyModule
  end
  
  def test_method_from_my_module
    obj = TestClass.new
    
    obj.method_from_my_module input_data
    
    assert_equal 'something', actual
  end
end