The output of waveshaper-simple.html is:

This is a testharness.js-based test.
PASS # AUDIT TASK RUNNER STARTED.
PASS > [simple] 
PASS   WaveShaper.curve is equal to null.
PASS   WaveShaper.oversample is equal to none.
PASS   Waveshaper.oversample = "2x" is equal to 2x.
PASS   Waveshaper.oversample = "4x" is equal to 4x.
PASS   Waveshaper.oversample = "invalid" is equal to 4x.
PASS   WaveShaper.curve is identical to the array [-1,0.25,0.75].
PASS   Waveshaper.curve = null is equal to null.
PASS < [simple] All assertions passed. (total 7 assertions)
PASS # AUDIT TASK RUNNER FINISHED: 1 tasks ran successfully.
Harness: the test ran to completion.

It's kind of hard to tell what all of this means.  It would be nice if
the test were a bit more verbose on what is happening so you can just
look at the output and get a sense of the actual tests being done.