There's an issue with the invocations of mocha --parallel in docker/test_js.sh which is used by the CI workflow. It seems that on some systems, this can fail silently.

To reproduce:

• Checkout 325b89b (prior to the chalk fix) and rebuild a container for testing.
• In the container, make this edit to a few lines in Makefile to speed up the example:

Old:

test-js: test-prairielearn test-prairielib test-grader-host test-workspace-host test-packages
test-prairielearn: start-support
        @yarn mocha --parallel "tests/**/*.test.{js,mjs}"

Modified: (The text here doesn't reflect this, but you need to use tabs, not spaces.)

test-js: test-prairielearn
test-prairielearn: start-support
        @yarn mocha --parallel "tests/access.test.js" "tests/database.test.js"
        echo finished with no error but should have failed

• Run: docker/test_js.sh. On a 4-core CPU, this seems to succeed with no error (but it should have failed).
• Now try again without --parallel. It should fail as expected.

Similarly, I note this behavior:

• Using --parallel --jobs 2 has the problem (test succeeds when it should not).
• Using --parallel --jobs 1 does not have the problem (test fails as expected).
• Using --bail --parallel --jobs 2 does not have the problem (test fails as expected).
• (Accordingly:) Using --bail --parallel (no jobs limit) does not have the problem (test fails as expected). Maybe this is an acceptable workaround for now?

This may be related to a bug with mocha's parallel mode that was previously reported: mochajs/mocha#4559