[SOLVED] .mocharc.json Not Loading in Docker Container

I am trying to run tests within an Ubuntu 18.04 docker container but I can’t get the values within .mocharc.json to load. My package.json contains the following script:

"scripts": {
  "test": "export MONGO_URL='' && TEST_CLIENT=0 meteor test --full-app --once --driver-package meteortesting:mocha --port 3001 --settings dev/settings-development.json",

And, I have a script that runs meteor npm test within the container and a simple .mocharc.json like this:

  "require": "imports/test/hooks.mjs",
  "grep": "Some tests"

But neither the hooks nor the grep work. Can anyone see what I am doing wrong? happy to add more information if required.
Thanks in advance.

Turns out when I thought I had checked versions, I hadn’t actually checked versions from within the docker container. It was still running meteortesting:mocha version 1.1.5. Updating that to 2.0.3 and meteortesting:mocha-core to 8.0.1 fixed my issue.
Lesson learnt.