+ event.button.button = SDL_BUTTON_X2 + 1;
+ CPPUNIT_ASSERT_EQUAL_MESSAGE(
+ "output format of SDL mouse button up event",
+ string("mouse button up: window ID: 5, mouse ID: 6, button: ") + to_string(int(SDL_BUTTON_X2 + 1)) + ", state: pressed, clicks: 7, position: 8 9", string_cast(event));