// TODO(user): Consider adding both error messages from here and {@link AbstractNetworkTest}
  // in one class (may be a utility class for error messages).
  private static final String ERROR_PARALLEL_EDGE = "connected by a different edge";
  private static final String ERROR_NEGATIVE_COUNT = "is non-negative";
  private static final String ERROR_ADDED_PARALLEL_EDGE =
      "Should not be allowed to add a parallel edge.";

            IllegalArgumentException.class, () -> networkAsMutableNetwork.addEdge(N4, N5, E12));
    assertThat(e).hasMessageThat().contains(ERROR_REUSE_EDGE);
    e = assertThrows(IllegalArgumentException.class, () -> addEdge(N2, N1, E12));
    assertThat(e).hasMessageThat().contains(ERROR_REUSE_EDGE);
  }

  @Test
  public void addEdge_parallelEdge_notAllowed() {
    assume().that(graphIsMutable()).isTrue();

    assertEquals(RUNTIME_EXCEPTION, expected);
  }

  public void testGetCheckedUntimed_Error() throws TwoArgConstructorException {
    try {
      getChecked(ERROR_FUTURE, TwoArgConstructorException.class);
    } catch (Error expected) {
      assertEquals(ERROR, expected);
      return;
    }
    fail();
  }

  // identifiable substrings of expected error messages, from Strings that we've defined
  // here to provide error messages.
  // TODO(user): Some Strings used in the subclasses can be added as static Strings
  // here too.
  static final String ERROR_MODIFIABLE_SET = "Set returned is unexpectedly modifiable";
  static final String ERROR_SELF_LOOP = "self-loops are not allowed";

    assertThat(e).hasMessageThat().contains(ERROR_PARALLEL_EDGE);
    e =
        assertThrows(
            IllegalArgumentException.class,
            () -> networkAsMutableNetwork.addEdge(N2, N1, EDGE_NOT_IN_GRAPH));
    assertThat(e).hasMessageThat().contains(ERROR_PARALLEL_EDGE);
  }

  @Test
  public void addEdge_parallelEdge_allowsParallelEdges() {

                }

                props.setProperty(key, Long.toString(System.currentTimeMillis()));

                if (error != null) {
                    props.setProperty(key + ERROR_KEY_SUFFIX, error);
                } else {
                    props.remove(key + ERROR_KEY_SUFFIX);
                }

                getLogger().debug("Writing resolution-state to: " + touchfile);

                Assume.assumeTrue("No Ntsmbs", false);
            }
            catch ( SmbException e ) {
                if ( e.getNtStatus() == NtStatus.NT_STATUS_ACCESS_DENIED || e.getNtStatus() == WinError.ERROR_ACCESS_DENIED ) {
                    // we might not have permissions for that
                    Assume.assumeTrue("No permission for share security accesss", false);
                }
                throw e;

  static final String ERROR_SELF_LOOP = "self-loops are not allowed";
  static final String ERROR_EDGE_NOT_IN_GRAPH =
      "Should not be allowed to pass an edge that is not an element of the graph.";
  static final String ERROR_ADDED_SELF_LOOP = "Should not be allowed to add a self-loop edge.";
  static final String ERROR_ADDED_PARALLEL_EDGE = "Should not be allowed to add a parallel edge.";
  static final String ERROR_ADDED_EXISTING_EDGE =

  static final String ERROR_SELF_LOOP = "self-loops are not allowed";
  static final String ERROR_EDGE_NOT_IN_GRAPH =
      "Should not be allowed to pass an edge that is not an element of the graph.";
  static final String ERROR_ADDED_SELF_LOOP = "Should not be allowed to add a self-loop edge.";
  static final String ERROR_ADDED_PARALLEL_EDGE = "Should not be allowed to add a parallel edge.";
  static final String ERROR_ADDED_EXISTING_EDGE =

  // TODO(user): Consider adding both error messages from here and {@link AbstractNetworkTest}
  // in one class (may be a utility class for error messages).
  private static final String ERROR_PARALLEL_EDGE = "connected by a different edge";
  private static final String ERROR_NEGATIVE_COUNT = "is non-negative";
  private static final String ERROR_ADDED_PARALLEL_EDGE =
      "Should not be allowed to add a parallel edge.";