public synchronized int size() {
        return this.layersList.size();
    }
@Test
    public void sizeTest() {
        Layers layers = new Layers(new DummyRedrawer(), new DisplayModel());
        Assert.assertEquals(0, layers.size());

        layers.add(new DummyLayer());
        Assert.assertEquals(1, layers.size());

        layers.clear();
        Assert.assertEquals(0, layers.size());
    }