Since at the moment, we don't have infrastructure in the wdspec tests to create a bidi-only session, in the scope of bug 1731730 for "session.new" command we introduced only gecko specific tests.

In the scope of this bug, we should prepare the infrastructure and migrate gecko specific tests.

Some points to consider:

• in wdspec tests we directly talk to Firefox while chrome has chromedriver sitting in-between. Probably we need the same as well for geckodriver when we want to have BiDi only support and get it tested on Android. Then geckodriver could forward the WebSocket to the device.
• we could in theory port the concept of browsers/executors to the wdspec tests, so we'd have a "browser" fixture that would know how to launch each specific browser (or driver). (browser fixture, used for gecko specific tests). But that would require a bit more work.

The infrastructure part is moved to bug1836785.
As soon as that bug is done, we should migrate session.new geckodriver specific tests to make them cross-browser.