private void verifyIsMockable(IMockMaker mockMaker, IMockCreationSettings settings) {
    IMockabilityResult result = isMockable(mockMaker, settings);
    if (!result.isMockable()) {
      throw new CannotCreateMockException(settings.getMockType(), ". " + mockMaker.getId() + ": " + result.getNotMockableReason());
    }
  }
Returns {@code true} if the passed class is a Spock static mock currently active on the current {@link Thread}.

@param clazz the class to check
@return {@code true} if this class is a Spock static mock currently active on the current {@code Thread}
spock-core/src/main/java/org/spockframework/mock/runtime/MockMakerRegistry.java