Even though I enabled the “Ignore SSL Certificate Errors” option, that seems to have no effect with Firefox browsers (works fine with Chrome though).
Any ideas?
Firefox disabled any way to ignore cert errors as a security measure so it no longer works for Firefox (at this point it may be Chrome and IE-only). The legacy Windows agent used to force it by intercepting the API calls internal to Firefox but that is no longer possible with the cross-platform agent.
The only way to do it now for Firefox is to run a private instance of WPT and install the certs (or a custom root) on the test machines so they see the self-signed certs as valid.
Ah that sucks, I remember it still being possible in recent versions of selenium.
Oh well…no more Firefox then.