No, that's the symptom; it just means it was still doing a PHPUnit thing when it hit the overall hard-limit of 60 mins. It's almost always caused by composer (packagist) or node (npm) taking an age to resolve, for whatever reason.

In T225167#5238653, @Jdforrester-WMF wrote:

No, that's the symptom; it just means it was still doing a PHPUnit thing when it hit the overall hard-limit of 60 mins. It's almost always caused by composer (packagist) or node (npm) taking an age to resolve, for whatever reason.

That doesn't seem right. Here I've switched the timestamps to elapsed time to make it clearer,

00:09:39.952 ..............Build timed out (after 60 minutes). Marking the build as failed.
01:00:00.033 Build was aborted

We've successfully made it through all the composer stuff (I don't think npm has been called yet), and at 9m39s we're running PHPUnit tests... the next thing that happens is 50 minutes later and it's the timeout. There should be nothing happening in the background.

Oh, system time vs. wall time on a contended resource? Eh.

I am 99,99% sure it is T220685. Well indeed looking at the mw-debug-cli.log file:

[PHPUnitCommand] Start test Scribunto_LuaSandboxInterpreterTest::testRoundtripNAN
[PHPUnitCommand] End test Scribunto_LuaSandboxInterpreterTest::testRoundtripNAN
[PHPUnitCommand] Start test Scribunto_LuaSandboxInterpreterTest::testTimeLimit