Mock observers globally in Jest
What does this MR do?
As JSDom is missing global mocks for Observers, we currently need to mock observers manually in any spec that might use them under the hood.
Our existing mocks are only working on one instance of observers each, so we have refactored them to work on multiple instances as well.
In order to improve the performance on tests where the Observers aren't tested, we add a NoopObserver to JSDom.
As an aside, JSDom actually implements a MutationObserver, so no need to mock it!
We do this, because once we remove our ResizeObserver polyfill from GitLab UI, we would be running into trouble otherwise!
Screenshots or Screencasts (strongly suggested)
N/A
How to setup and validate locally (strongly suggested)
Does this MR meet the acceptance criteria?
Conformity
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I have self-reviewed this MR per code review guidelines. -
This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines) -
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This change is backwards compatible across updates, or this does not apply.
Availability and Testing
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I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.) -
I have tested this MR in all supported browsers, or it's not needed. -
I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.
Security
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Label as security and @ mention @gitlab-com/gl-security/appsec -
The MR includes necessary changes to maintain consistency between UI, API, email, or other methods -
Security reports checked/validated by a reviewer from the AppSec team