Tommy Giardina

Thanks for the quick reply! If I end up liking Atom enough to stick with it, maybe I'll look into trying to implement this myself.

This is a pretty big problem! A lot of people use Jest with SuperTest. But currently Jest's `--detectOpenHandles` doesn't work for a big chunk of its users (see [here](https://github.com/facebook/jest/issues/9473)). So...

I can reproduce this 100% of the time by running: ``` git clone 'https://github.com/hypothesis/client.git' cd client make dev ``` It hangs at `Built sidebar.bundle.js`: ``` yarn install yarn install v1.22.10...

@GithubGY Oops, you're right! web-ext-types does include `onMessage.sender`. That's a typo on my part. Like you, I was actually interested in the `addListener` callback. I edited my issue to reflect...