(In principle, I agree, but in my own tests, I've been stuffing multiple related tests into a single case in order to save on setup/teardown -- creating a new CodeMirror instance is cheap, but not trivially so. The 400+ vim tests are currently taking up the majority of the time it takes to run the test suite, and, in practice, a slower test suite means it is run less. Maybe we should look into optimizing the vim tests by reusing an editor and resetting it?)