Maybe something like this?

```python
class OtterApp(Klein):
    def route(self, *args, **kwargs):
        kwargs['strict_slashes'] = False
        return super(OtterApp, self).route(*args, **kwargs)
```

Then you really only have to write test-cases for `OtterApp`.

The subclassing is sub-optimal but the version using composition is kind of a pain since you can't use something like `proxyForInterface` (because there is no interface to be used.)