Integration tests for subscriptions
The test-suite is great to ensure that an Apollo server integration is working well. However, as far as I'm aware, it does not include tests for subscription support. Would be nice if this could be optionally included (similar to the existing `noIncrementalDelivery` switch).

Maybe helpful: https://gist.github.com/patrixr/2536ee396d488bd5e38b0278513eefeb