sys/test_utils/dummy_thread: initial commit

[kaspar030]

Contribution description

While looking at # #14181, I needed a quick way to add a thread. So this dummy thread module was born. If used, the module will start a dummy thread that only sleeps, in auto_init().

Use like this, to trick tests that assume a constant number of threads:

USEMODULE+=dummy_thread make -Ctests/rmutex flash test.

This module is not used otherwise.

Testing procedure

Issues/PRs references

[bergzand]

Ack, please squash.

Are you sure we should skip the compile test?

[kaspar030]

Are you sure we should skip the compile test?

it is not used anywhere...

[bergzand]

it is not used anywhere...

I'm a bit hesistant with merging what is effectively dead code, but I don't really see the need to add a separate test for this. Does it make sense to add this as a default module to one of the tests, maybe just the unittests?

[kaspar030]

Does it make sense to add this as a default module to one of the tests, maybe just the unittests?

OK, it'll increase RAM usage like if adding another idle thread, let's see if that's ok.

[kaspar030]

OK, it'll increase RAM usage like if adding another idle thread, let's see if that's ok.

I added it to tests/test_utils, seems most fitting.