Testing: Test case for serving static files

[amotl]

Observations

Coming from GH-562, uninstalling whitenoise (and servestatic) made no difference on the outcome of the test suite: It still succeeded.

Thoughts

Responder should at least have a basic software test case which ensures serving static files works well? Or are the static file serving support packages like WhiteNoise and ServeStatic just an optional extension, used on demand when they're installed, otherwise the machinery is falling back to a slower(?) default method?

I guess the most occam's razor like explanation is that a corresponding test case is just missing, and should be added?

Thank you in advance for educating me about this area of the framework, and where I am wrong about my assumptions.

/cc @Archmonger