void recompiledClasses(String... classNames) {
        assert changedFileNames == asSet(classNames)
    }

    void recompiledFqn(String... classNames) {
        assert getChangedFileNames(true) == asSet(classNames)
    }

    //asserts files deleted since last snapshot.
    void deletedFiles(String... fileNames) {
        def expectedNames = fileNames.collect({ removeExtension(it) }) as Set