title: NoMethodError <fixture name> in Rails and minitest/spec
body: <p>Without minitest/spec, the test looks like this, and the <code>my_engine_customers</code> fixtures are loaded (all is well):</p>
  
  <p><code>my_engine/test/models/my_engine/customer_test.rb</code> is</p>
  
  <pre><code>require 'test_helper'
  
  module MyEngine
    class CustomerTest &lt; ActiveSupport::TestCase
  
      test "alex is id 5" do
        assert my_engine_customers(:alex).id, 5
      end
  
    end
  end
  </code></pre>
  
  <p>After adding <code>require 'minitest/autorun'</code> to <code>test/test_helper.rb</code>, and then
  converting the above test :</p>
  
  <pre><code>require 'test_helper'
  
  describe MyEngine::Customer do
  
    let(:alex) { my_engine_customers(:alex) } # error here (error shown below)
  
    it "alex is id 5" do
      assert alex.id, 5
    end
  
  end
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>NoMethodError: undefined method `my_engine_customers' for
  #&lt;#&lt;Class:0x007fb63e8f09e8&gt;:0x007fb63e81b068&gt;
  </code></pre>
  
  <p>How do I access fixtures when using minitest/spec ?</p>