There are a handful of console tests which are disabled when Fission is not enabled (https://searchfox.org/mozilla-central/search?q=skip-if+%3D+%21fission&path=devtools%2Fclient%2F&case=false&regexp=false)
This is because the context selector is based on top of targets, and until Bug 1685500 is created, we won't create targets for the remote iframes when fission is disabled.

Once Bug 1685500 is done, we should be able to enable those test even when fission is disabled.
We might also take this as an opportunity to add cases with same-origin iframes.