Observations:

• having node_modules installed in one folder (e.g. /opt/lib/) and the application code & tests in another (e.g. /srv/service) does seem to pose a challenge to, presumably amongst others, jest' <rootFolder> (cf. 1 2) - documentation on NODE_PATH says "It is strongly encouraged to place dependencies in the local node_modules folder. These will be loaded faster, and more reliably."

Running in CI:

e.g. https://gerrit.wikimedia.org/r/c/mediawiki/services/mathoid/+/454295 invoking https://integration.wikimedia.org/ci/job/trigger-service-pipeline-test-only/ invoking https://integration.wikimedia.org/ci/job/service-pipeline-test-only/ building like https://integration.wikimedia.org/ci/job/service-pipeline-test-only/92/consoleText - effectively running blubber .pipeline/blubber.yaml test (compare https://github.com/wmde/wikibase-termbox/pull/104/files#diff-2)

https://github.com/wikimedia/integration-config/blob/master/zuul/layout.yaml#L7030
should be it once we have the repo in shape.