}
  }

  /** Returns the product of {@code n1} exclusive through {@code n2} inclusive. */
  @SuppressWarnings("UseCorrectAssertInTests") // TODO(b/345814817): Remove or convert assertion.
  private static BigInteger oldSlowFactorial(int n1, int n2) {
    assert n1 <= n2;
    if (IntMath.log2(n2, CEILING) * (n2 - n1) < Long.SIZE - 1) {
      // the result will definitely fit into a long
      long result = 1;

    }
  }

  /** Returns the product of {@code n1} exclusive through {@code n2} inclusive. */
  @SuppressWarnings("UseCorrectAssertInTests") // TODO(b/345814817): Remove or convert assertion.
  private static BigInteger oldSlowFactorial(int n1, int n2) {
    assert n1 <= n2;
    if (IntMath.log2(n2, CEILING) * (n2 - n1) < Long.SIZE - 1) {
      // the result will definitely fit into a long
      long result = 1;

    }
  }

  public <N1 extends Number, N2 extends Number, N11 extends N1>
      void testisSupertypeOf_typeVariable() {
    assertAssignable(
        TypeToken.of(new TypeCapture<N1>() {}.capture()),
        TypeToken.of(new TypeCapture<N1>() {}.capture()));
    assertNotAssignable(new TypeToken<List<N11>>() {}, new TypeToken<List<N1>>() {});
    assertNotAssignable(

    addEdge(N1, N1, E11);
    assertThat(network.degree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.inDegree(N1)).isEqualTo(1);
    addEdge(N4, N1, E41);
    assertThat(network.inDegree(N1)).isEqualTo(2);
  }

    addEdge(N1, N1, E11);
    assertThat(network.degree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.inDegree(N1)).isEqualTo(1);
    addEdge(N4, N1, E41);
    assertThat(network.inDegree(N1)).isEqualTo(2);
  }

    putEdge(N1, N2);
    assertThat(graph.predecessors(N1)).containsExactly(N1, N2);
  }

  @Test
  public void successors_selfLoop() {
    assume().that(graph.allowsSelfLoops()).isTrue();

    putEdge(N1, N1);
    assertThat(graph.successors(N1)).containsExactly(N1);
    putEdge(N2, N1);
    assertThat(graph.successors(N1)).containsExactly(N1, N2);
  }

  @Test
  public void incidentEdges_selfLoop() {

    addEdge(N1, N1, E11);
    addEdge(N1, N1, E11_A);
    addEdge(N1, N2, E12);
    assertTrue(networkAsMutableNetwork.removeEdge(E11_A));
    assertThat(network.edgesConnecting(N1, N1)).containsExactly(E11);
    assertThat(network.edgesConnecting(N1, N2)).containsExactly(E12);
    assertTrue(networkAsMutableNetwork.removeEdge(E11));
    assertThat(network.edgesConnecting(N1, N1)).isEmpty();

    addEdge(N1, N1, E11);
    assertThat(network.successors(N1)).containsExactly(N1);
    addEdge(N2, N1, E12);
    assertThat(network.successors(N1)).containsExactly(N1, N2);
  }

  @Test
  public void degree_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.degree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.degree(N1)).isEqualTo(3);

    putEdge(N1, N2);
    assertThat(graph.predecessors(N1)).containsExactly(N1, N2);
  }

  @Test
  public void successors_selfLoop() {
    assume().that(graph.allowsSelfLoops()).isTrue();

    putEdge(N1, N1);
    assertThat(graph.successors(N1)).containsExactly(N1);
    putEdge(N2, N1);
    assertThat(graph.successors(N1)).containsExactly(N1, N2);
  }

  @Test
  public void incidentEdges_selfLoop() {

    putEdge(N1, N1);
    putEdge(N1, N2);
    assertThat(graph.adjacentNodes(N1)).containsExactly(N1, N2);
  }

  @Test
  public void predecessors_selfLoop() {
    assume().that(graph.allowsSelfLoops()).isTrue();

    putEdge(N1, N1);
    assertThat(graph.predecessors(N1)).containsExactly(N1);
    putEdge(N4, N1);
    assertThat(graph.predecessors(N1)).containsExactly(N1, N4);
  }

  @Test