Test 0 : at the initial zoom the WMS layer is in range, you should therefore see the 'Loading tiles...' message when loading the page for the first time.

Test 1 : If you zoom out by one level (using the zoombar), the WMS layer becomes out of range. No tile should be loaded so you shouldn't see the 'Loading tiles...' message.

Test 2 : Zoom in by one level to go back to initial state (the WMS is back). Open the layer switcher and turn off the WMS layer. No tile should be loaded so you shouldn't see the 'Loading tiles...' message.

Test 3 : Keep the WMS layer turned off in the layer switcher. Zoom out by one level again. The layer is both invisible and out of range, so you shouldn't see the 'Loading tiles...' message.