I cloned the repo from https://github.com/paulegradie/Sailfish in order to write my own TestAdapter for VS. To try it out I just built the project and called this command:

vstest.console SailfishsourceTests.TestAdapterbinDebugnet8.0Tests.TestAdapter.dll /TestAdapterPath:SailfishsourceSailfish.TestAdapterbinDebugnet8.0

which runs perfectly fine all of the tests in the assembly.

In order to verify the adapter is actually loaded, I added a Debugger.Launch-statetemt to the implementation of ITestDiscoverer.

This works great so far. However when I add a breakpoint to the implementation of the ITestExecutor-interface, nothing is hit at all (the breakpoint is filled normal, so the code matches the assembly being run). So I added another breakpoint into some of the tests within Tests.TestAdapter.dll in order to examine the stacktrace. Interestingly there’s no indication that that implementation is used at all, as seen in this pic: