Speed up or parallelise test job

The test job takes quite long at the moment (~17 mins).

My understanding is that this is (a) because the runner uses -j1 so that the individual tests don't fail because they step on each other's feet (e.g. trying to use same ports or somesuch), (b) the test running is not parallelised across multiple jobs using some (new?) mechanism gitlab provides.

My question is: can we do something simpler here as first step?

For example: test within the same module should always be possible to run in parallel since that's how make check / ninja test is run by default when building the module already, so should mostly work really.

Could we just sequentially run all tests for gstreamer / gst-plugins-base / etc. but parallelised for each module?