### Question:
DefaultContainerCascade implements ContainerCascade { @Override public boolean hasNode(String nodeId) { for (IdentifiedPolygon node : nodes) { if (node.id.equals(nodeId)) { return true; } } return false; }  void add(final IdentifiedPolygon node); void add(FlexibleArrow element); @Override void colorNode(String nodeId, RGBColor fillColor); @Override void addTo(PolygonPanel panel); @Override void addToggleListener(NodeToggleListener listener); @Override void removeToggleListener(NodeToggleListener listener); @Override void initNodeNames(NodePresentationProperties properties); @Override void determinePositionFor(String nodeId, ShapeWithPosition control); @Override boolean hasNode(String nodeId); void moveBy(double x, double y);  }### Answer:
@Test public void hasNodeWithId() throws Exception { assertThat(container.hasNode("X"), is(true)); }
@Test public void doesNotHaveNodeWithDifferentId() throws Exception { assertThat(container.hasNode("Z"), is(false)); }