I like the idea of testing build-system behaviors like this, and I don’t think it’s ever really done in practice. Scriptable build systems, for lack of a better name for them, exist at a bad intersection of Turing complete, hard to test different cases, hard to reason about, hard to read the build script code, and most of us treating them as “ugh I hope all this stuff works” and if it does “thank god I get to ignore all this stuff for another 6 months”.