This test opens the context menu and chooses Inspect while a page load is in progress.
It looks like the context menu may not open in some cases under these circumstances.

Before bug 1706806, it wasn't waiting for the menu to open, and the test passes even if Inspect isn't clicked. So it wasn't doing what it was trying to do.

I tried to fix this in bug 1706806, but as a result, the test started to time out.

https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&revision=0bc6d559d01347f397c4af074cf7f36990653ce0&test_paths=devtools%2Fclient%2Finspector%2Fmarkup%2Ftest%2F

It's only timing out on macOS, but there's not really a reason why this should be mac-only. It's probably timing-dependent in some way, so it might intermittently happen on other platforms, too.

This test is now disabled on all platforms.