Xcode 6 is running disabled unit tests

I've got a weird problem with Xcode 6 (6.1.1). I have a test target in which most of the testclasses are disabled (aka. greyed out in the test navigator). Still, when I try to run the remaining tests (or even when I specifically select a test from the test navigator to run) sometimes, Xcode also runs the disabled tests. This doesn't always happen but when it does, the only solution to prevent Xcode from running the disabled tests is to remove them from the target. The issue looks very similar to this question. Since I am not doing UI tests I opened a new one.

Has anybody else witnessed this behaviour? Might it be a bug in Xcode 6 or could I somehow have messed up my project. I would like to provide you with some settings or code but I have no clue what is relevant in the fist place.

PS: As an interesting (and maybe unrelated) side note: When I try to run any test through the small "play" indicator left of the source code, Xcode tells me that it can't build the project but doesn't display any errors. When I run the same test through the test navigator, it works like a charm...