Flaky Firefox WebRTC test

[achingbrain]

Sometimes the receiving end of the can send a large file WebRTC test doesn't receive all of the bytes when running in Firefox, Chrome is fine:

  1) basics
       can send a large file:

      expected Uint8Array[ 0, 0, 0, 0, 0, 0, 0, …(5242845) ] to equal Uint8Array[ 0, 0, 0, 0, 0, 0, 0, …(5242881) ]
      + expected - actual

This fails in CI quite often and can be reproduced locally too.

It seems to happen when there are several datachannels open on the connection simultaneously so may be related to https://bugzilla.mozilla.org/show_bug.cgi?id=1902850 - the fix for this should ship in Firefox 129 on August 6th, though we need to wait for that version of FF to be included in playwright to verify the fix.

[achingbrain]

It seems to happen when there are several datachannels open on the connection simultaneously

I don't think this is the case, it still happens if I add a delay in the test to ensure there are no other streams open.

Investigation continues.

[SgtPooki]

looks like playwright has the latest Firefox set, but hasn't released an updated version to NPM yet: microsoft/playwright@5cc1e7b

[tabcat]

This looks to be resolved as I cannot get the test to fail in Firefox. The Firefox version used by playwright-core is 131. https://bugzilla.mozilla.org/show_bug.cgi?id=1902850 changes have been present since 129.

[achingbrain]

CI is still really flaky around these tests & it’s really hard to replicate it locally 😩