Angular Testing Library with combination of HappyDom instead of JSDOM

[jarekcimoch]

Hello, I'm using HappyDom instead of JSDOM and I have following issue.

when I do something like
await screen.findByText(optionLabel);

observer.observe is not a function TypeError: observer.observe is not a function

at C:\Ohpen\cloned-2\mfes-broker-app-angular\src\node_modules\@testing-library\dom\dist\wait-for.js:96:16

HappyDom is supporting MutationObserver and I guess JSDOM was not out of the box hance some logic there is used.
Could it be fixed? Or can I fix it somehow myself?

[timdeschryver]

We expect the tests to be run in a DOM-like environment.
This also means that there's a MutationObserver observer available to react to dom changes.
A workaround is to run all tests in a "fake timers context", which doesn't use the observer.

[jarekcimoch]

@timdeschryver HappyDom is DOM-like env, it has MutiationObserver in place

[timdeschryver]

@jarekcimoch do you have a reproduction that I can use to test this?

[matdv]

capricorn86/happy-dom#1514 (comment)

This error still occurs but there is a workaround in this linked issue.
It seems to be related to jest-preset-angular patching the MutationObserver.