Some tests time out in GitHub actions

[rien]

Sometimes the CI fails with ava reporting Timed out while running tests, the message is quite unhelpful because it does not report which tests have timed out (avajs/ava#2639), but when comparing with a succeeded test run, it seems that both fragment.ts tests time out.

It does not feel as if it is a slow runner: both tests complete within 2s on my computer and the default timeout per test be 10s. I think this could be caused by ava trying to run tests in parallel, with only once CPU being available, thus causing some locking issues.

I will try running the tests with --serial and see if this problem occurs again.

[rien]

This hasn't occurred in a while.