@Test
public void testSetNullTileSource() {

    NicTileSource tileSource = mock(NicTileSource.class);
    // Only required by the super-constructor:
    IRegisterReceiver registerReceiver = mock(IRegisterReceiver.class);
    AssetTileProvider atp = new AssetTileProvider(registerReceiver, tileSource, null);
    try {
        atp.setTileSource(null);
        fail("tileSource == null should throw an exception. We don't want NPE later on.");
    } catch (IllegalArgumentException ex) {
        // Fine!
    }
}