The "Details" panel for bug 1501502 contains this: > Code Coverage: 9 lines covered out of 20 lines added (d29131a84168) The link points to: https://firefox-code-coverage.herokuapp.com/#/changeset/d29131a84168 Actual results: Most of the test is not marked "covered". Expected results: It should be covered. The test would fail if reportCompare() wasn't called. I confirmed locally that the test passes and a `print("OK");` on the last line is reached.

I tried troubleshooting this a bit with Nicolas. We didn't get far. Some test output we generated is in: https://gist.github.com/jorendorff/76ef3546b714172a52c80ec9ec937479 I can't get any lcov output locally using `--code-coverage` and `JS_CODE_COVERAGE_OUTPUT_DIR=`, just empty files. We think that's unrelated and probably my fault. :)