Can you give me a bit of background of the FindInFiles issues (the ones you are fixing here)?

Sure.

• should disable the Replace button if query is empty
  As FindBar now remembers the last query, the bar is pre-filled in this test case, whereas it tests the case when the bar is empty. We had the same test fixes for FindReplace in Fix FindReplace Integration tests #12440.
• should expand/collapse items when clicked
  I highly doubt this test has ever worked. #items is not an actual element to be found in our DOM, but a Mustache section. The new selectors select the actual elements that need to be checked. The tr one is that verbose because we don't really have another way to separate tr.disclosure-triangle from "normal" tr rows.

Thank you.

The SVG test looks fine.
For the first issue of FindInFiles, can you put the function to clean the searchbar in a beforeEach function in that describe section? If it doesn't cause other issues I would prefer it.
For the second issue I think the point of the test was to check that all lines of a specific list were hidden, with your change you are checking only the first one. I think an option could be to add another class and check for it.

Semi related: when running the FindInFiles test I saw a couple of exception logged in the Developer Tools of test window. Maybe some other timing issue...

I cannot move that expression into the beforeEach function because #find-what is not part of the DOM at this point, and I also cannot move it into openSearchBar because some other tests rely on the bar being pre-populated from a selection (and we can't really distinguish where it comes from).

I've also altered the test so two results are checked, and we now make sure all of the results are hidden or visible, respectively.

I cannot move that

Thank you to have checked!
If tests pass then LGTM.