### Question:
Layers implements Iterable<Layer>, RandomAccess { public synchronized boolean isEmpty() { return this.layersList.isEmpty(); } Layers(Redrawer redrawer, DisplayModel displayModel); synchronized void add(int index, Layer layer); synchronized void add(Layer layer); synchronized void addAll(Collection<Layer> layers); synchronized void addAll(int index, Collection<Layer> layers); synchronized void clear(); synchronized boolean contains(Layer layer); synchronized Layer get(int index); synchronized int indexOf(Layer layer); synchronized boolean isEmpty(); @Override synchronized Iterator<Layer> iterator(); synchronized Layer remove(int index); synchronized boolean remove(Layer layer); synchronized int size();  }### Answer:
@Test public void isEmptyTest() { Layers layers = new Layers(new DummyRedrawer(), new DisplayModel()); Assert.assertTrue(layers.isEmpty()); layers.add(new DummyLayer()); Assert.assertFalse(layers.isEmpty()); layers.clear(); Assert.assertTrue(layers.isEmpty()); }