We currently launch and then close the empty browser. This does not
trigger many codepaths related to web page process creation and
browser context.
With opening and navigating a page, we do a more real-life test.
This exposes an issue from #3740.
Our current tests excercise the same-process launchServer/connect
combination. This change adds tests for remote server and immediately
exposes a bug with selector engines.
This patch moves fixtures.js to base.fixtures.ts that sits next to tests. All tests get an extra import to get the base fixtures (both types and implementations).