running tests inside a container?

Is anyone doing CodeMirror development inside a docker container?
I was able to get everything setup and run the tests to get an “All passed” message.
However, when I add a failing test and run npm test again, it still returns “All passed”!

I’ve been able to get the tests running correctly on two different systems using “normal” (non-containerized) node.js installs.
See below for the contents of my Dockerfile, I’ve tried both the node:10-slim and the node:10 base images.

Any ideas or requests for more info would be appreciated.

FROM node:10-slim


RUN npm install -g nodemon
# Install PhantomJS dependencies
RUN apt-get update && apt-get install --no-install-recommends -y \
    bzip2 \
	libfontconfig1 \
	fontconfig \
	libfontconfig1-dev \
	libfreetype6-dev \
	&& rm -rf /var/lib/apt/lists/*

RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

# Don't run `npm install` or `npm run build` steps here.
# After running container, will need to `docker exec -it` into it and `npm install` then
# Run nodemon to have a long-lived process to keep container running
CMD [ "nodemon" ]

TL;DR - There’s nothing wrong with running the test suite inside a container.
I’m a very silly person who can’t see my own typo in the keyword function.
I finally spotted the error in the browser dev tools console.

All of this started so that I can have a CodeMirror dev repo on my VPS…without installing anything on my work laptop (the admins at my company are strict and I’m too cheap to buy my own).
But I certainly learned lots before fixing my typo!:

  • I changed my Dockerfile to use nodemon --inspector-brk= to start debugger and break on 1st line of node ./test/run.js
    • With the appropriate port available via an ssh-tunnel, I remotely connected from Chrome dev tools on my laptop to the container running on my VPS
      • Chrome has node-specific dev tools which appeared automatically as a green icon within the menus once I’d loaded in a new tab.
      • Breakpoints didn’t work, but I was able to single step through the running test suite and CodeMirror modules and look at stuff (I mostly just got more confused).
    • Somehow, I ended up unable to run npm test anymore from w/in my container, but while it was trying to run, I was able to load and run tests in browser.
      • That’s where I finally saw the console error in vim_test.js…ON THE EXACT LINE NUMBER WHERE I ADDED MY NEW TEST!!!
        • It was a SyntaxError: missing ) after argument list, which got me to a good page on MDN, but I still had trouble seeing my typo.
  • I also installed mosh on my VPS and the client chrome extension on my laptop (thankfully, I’m allowed to install my own extensions on the work laptop).
    • Mosh handles all network changes gracefully, no more dropped connections when switching wifi networks.
    • It’s nice to just leave that window open and not have to lose my place while looking through CodeMirror codebase

In the end, I didn’t even need the container, I added the path to /test/index.html under my CodeMirror dev directory as an nginx location so I can run tests in browser from my own custom URL.
So maybe my question should have been, “does it ever make sense to run CodeMirror tests from the command line?”.
I usually get an ‘All passed’ message on the CLI, even if there are failures running in the browser.
There’s probably a deep rabbit-hole here related to browser-version incompatabilites between Phantom running on the CLI and the current version of Chrome, so I won’t hold my breath waiting for an answer to that one.