title: NUnit TestCaseSource returns the same data for different yields
body: <p>I have the issue with NUnit framework and TestCaseSourse.
  I have some test data:</p>
  
  <pre><code>public TestData[] data = new TestDataBuilder()
                  .Add("inputFile", "132JoinTest.xml")
                  .AddRange("delimiter", ";", "")
                  .AddAllSubsets("sectionNames", new string[] { "Headline", "Byline", "Summary" }).GetTestData();
  </code></pre>
  
  <p>Also I have the data for TestCaseSource:</p>
  
  <pre><code>public IEnumerable&lt;TestCaseData&gt; ReduceTagsNumber
  {
      get
      {
          yield return new TestCaseData(data[0]);
          yield return new TestCaseData(data[1]);
      }
  }
  [TestCaseSource("ReduceTagsNumber")]
  public void Execute_ForInputThatCouldBeJoined_ReduceTagsNumber(TestData data)
  {
      //some code here
  }
  </code></pre>
  
  <p>I double check, that data[0] and data[1] contains the different data. But when I run NUnit tests both of them are runned with data[0]. I try to implement this in the different ways, but always the same result.
  Note: If i use the TestData structure instead the TestData class the Nunit doesn't see the second testCase at all.</p>