Elizabeth Figura (@zfigura) commented about dlls/setupapi/tests/devinst.c:
todo_wine ok(count == 4, "expected count==4, got %lu(%s)\n", count, cn);
/* Test Strings substitution */
WritePrivateProfileStringA("Version", "Class", "%ClassName%", filename);
WritePrivateProfileStringA("Version", "ClassGUID", "%ClassGuid%", filename);
/* Without Strings section the ClassGUID is invalid */
retval = SetupDiGetINFClassA(filename, &guid, cn, MAX_PATH, NULL);
ok(!retval, "expected SetupDiGetINFClassA to fail because ClassGUID is invalid (has non-substituted strkey token)!\n");
This should test the last error.