In WebKit, we have some tests using testRunner.terminateNetworkProcess(). It turned out that mac-wk2-stress-tests do not work with that functionality. Maybe, killing a process will cause some trouble with guard-malloc configuration?
For reference, failed build seems to be https://ews-build.webkit.org/#/builders/62/builds/516 for Attachment 425589 [details]. These tests are failing in guard-malloc mode.
What is the exact symptom of them not working?
<rdar://problem/76564233>