anchor.diff:            layers = new TestLayers({'Base': baseLayer})..addTo(map);
   
           //var spy = sinon.spy(layers, '_update');
  +        layers.resetTest();
   
           map.addLayer(overlay);
           map.removeLayer(overlay);
   
  -        expect(new Future.delayed(const Duration(seconds: 1), () {
  +        expect(new Future.delayed(const Duration(milliseconds: 500), () {
             expect(layers.called, isFalse);
           }), completes);
         });
  
positive.code:     callCount++;
      super.update();
    }
  }
negative.code:         map.setView(new LatLng(0, 0), 14);
        });
  
        test('when an included layer is added or removed', () {
          final baseLayer = new TileLayer(),
            overlay = new Marker(new LatLng(0, 0)),
            layers = new TestLayers({'Base': baseLayer}, {'Overlay': overlay})..addTo(map);
  
          //var spy = sinon.spy(layers, '_update');
          layers.resetTest();
  
          map.addLayer(overlay);
          map.removeLayer(overlay);
  
          expect(new Future.delayed(const Duration(milliseconds: 500), () {
            expect(layers.called, isTrue);
            expect(layers.callCount, equals(2));
          }), completes);
  