Take for instance this run https://build.webkit.org/results/GTK-Linux-64-bit-Release-GTK4-Tests/268120@main%20(29704)/results.html Dozens of tests are timing out with this error: "FAIL: Timed out waiting for notifyDone to be called" However, running the same tests individually, most of them pass. Also, when running the tests with --run-singly (so that each test invocation starts its own test runner process), the tests don't time out either. So this is likely to be a problem in the state of the test runner processes that gets broken at some point, and subsequent tests ran in the same WTR start timing out. We need to figure out why this is happening so that the GTK4 test bot is useful, otherwise CI is exiting early due to the number of timeouts.