@Test
public void moveDown() {

    layerHash.moveDown(obj1);
    assertEquals(obj3, layerHash.getKeysAsList().get(0));
    assertEquals(obj1, layerHash.getKeysAsList().get(1));
    assertEquals(obj2, layerHash.getKeysAsList().get(2));
    layerHash.moveDown(obj1);
    assertEquals(obj1, layerHash.getKeysAsList().get(0));
    assertEquals(obj3, layerHash.getKeysAsList().get(1));
    assertEquals(obj2, layerHash.getKeysAsList().get(2));
    layerHash.moveDown(obj1);
    assertEquals(obj1, layerHash.getKeysAsList().get(0));
    assertEquals(obj3, layerHash.getKeysAsList().get(1));
    assertEquals(obj2, layerHash.getKeysAsList().get(2));
}