private static final String E21 = "2-1";
  private static final String E13 = "1-3";
  private static final String E44 = "4-4";

  // Test for EndpointPair class

  @Test
  public void testOrderedEndpointPair() {
    EndpointPair<String> ordered = EndpointPair.ordered("source", "target");
    assertThat(ordered.isOrdered()).isTrue();
    assertThat(ordered).containsExactly("source", "target").inOrder();