javascript – Unit testing multiple features in one test

I’m writing a small utility class to create an abstraction for addEventListener (JavaScript/DOM)

Let’s say I have to test for these features:

  1. Single event target with a single event
  2. Multiple events
  3. Multiple event targets
  4. Delegated events
  5. Once

Now if I understand unit testing properly, I should create a test for each feature.

However, is there a need to test combined features? E.g.

  1. Multiple events + multiple targets
  2. Multiple event targets + delegated events
  3. Multiple event targets + delegated events + multiple events

Should I implement those combined tests in addition to single feature tests, or should I believe that I am fully covered by the single feature tests?