Tests have started failing on Firefox

Describe the bug Two out of 11 test-runs fail on GitHub, as seen on pr #1428:

Test / test (windows-latest, FirefoxHeadless) (pull_request):

FAILED TESTS:
H.264 Decoder Functional Test
✖ should handle H.264 rect
  Firefox 130.0 (Windows 10)
Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

✖ should handle specific context reset
  Firefox 130.0 (Windows 10)
Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

✖ should handle global context reset
  Firefox 130.0 (Windows 10)
Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

Test / test (ubuntu-latest, FirefoxHeadless) (pull_request):

FAILED TESTS:
H.264 Decoder Functional Test
✖ should handle H.264 rect
  Firefox 130.0 (Ubuntu 0.0.0)
Failed to decode frame: Operation is not supported
_handleError@core/decoders/h264.js:145:15
error@core/decoders/h264.js:152:34

✖ should handle specific context reset
  Firefox 130.0 (Ubuntu 0.0.0)
Failed to decode frame: Operation is not supported
_handleError@core/decoders/h264.js:145:15
error@core/decoders/h264.js:152:34

✖ should handle global context reset
  Firefox 130.0 (Ubuntu 0.0.0)
Failed to decode frame: Operation is not supported
_handleError@core/decoders/h264.js:145:15
error@core/decoders/h264.js:152:34

Additional context

It seems all failed tests have something to do with H.264 on Firefox, @any1 could it be that Firefox now has support for this? Perhaps the unit tests need to be modified somehow.

I cannot reproduce the issue myself on Linux, all unit tests work on my workstation, both in Firefox 131 and Chrome 129.

But in Firefox on Windows 11, I get this error instead:

FAILED TESTS:
    Protocol Initialization States
      Authentication
        RSA-AES Authentication (type 6) Handler
          ✖ "before all" hook for "should fire the serververification event"
            Firefox 131.0 (Windows 10)
          Trying to stub property 'generateKey' of undefined
          throwOnFalsyObject@http://samuel.lkpg.cendio.se:9876node_modules/sinon/pkg/sinon-esm.js:4146:15
          stub@http://samuel.lkpg.cendio.se:9876node_modules/sinon/pkg/sinon-esm.js:3959:24
          stub@http://samuel.lkpg.cendio.se:9876node_modules/sinon/pkg/sinon-esm.js:3435:39
          @http://samuel.lkpg.cendio.se:9876tests/test.rfb.js:1445:27

          ✖ "after all" hook for "should send credentials to server"
            Firefox 131.0 (Windows 10)
          window.crypto.subtle is undefined
          @http://samuel.lkpg.cendio.se:9876tests/test.rfb.js:1449:21

        ARD Authentication (type 30) Handler
          ✖ should return properly encrypted credentials and public key
            Firefox 131.0 (Windows 10)
          Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

novnc / noVNC

Tests have started failing on Firefox #1904