worker: improve coverage
This improves the worker coverage by using internal/assert
instead
of relying on assert
in case a faulty worker message type is
received (AFAIK this is only set internally, if it's public, this should be replaced with a test).
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines