Used to decorate xUnit.net test classes and collections to indicate a test which has
per-test-collection fixture data. An instance of the fixture data is initialized just before
the first test in the collection is run, and if it implements IDisposable, is disposed
after the last test in the collection is run. To gain access to the fixture data from
inside the test, a constructor argument should be added to the test class which
exactly matches the TFixture.