Instead of 
```
            choices = list(filterspec.choices(changelist))
            self.assertEqual(len(choices), len(expected_displays))
            for i, display in enumerate(expected_displays):
                self.assertEqual(choices[i]['display'], display)
```
you can write
```
            choices = tuple(c['display'] for c in filterspec.choices(changelist))
            self.assertEqual(choices, expected_displays)
```