I've got a suite of tests running using --isolate, since I'm sharing some ports, thus the vows can only be run synchronously :(
The problem is that if I do:
vows --isolate --cover-plain ./test-instrumented/*.js
I see my result from the vows test, but the js-coverage output is non-existent.
This is likely fixed in the latest vows. Can you retry and see if the issue persists?