// them to ensure that the validation check happens and has the expected behavior.
    assertNodeRemovedFromGraphErrorMessage(
        assertThrows(IllegalStateException.class, n1AdjacentNodes::size));
    assertNodeRemovedFromGraphErrorMessage(
        assertThrows(IllegalStateException.class, n1Predecessors::size));
    assertNodeRemovedFromGraphErrorMessage(
        assertThrows(IllegalStateException.class, n1Successors::size));

    assertThat(throwable).hasMessageThat().startsWith(EDGE_STRING);
    assertThat(throwable).hasMessageThat().contains(ERROR_ELEMENT_NOT_IN_GRAPH);
  }

  static void assertNodeRemovedFromGraphErrorMessage(Throwable throwable) {
    assertThat(throwable).hasMessageThat().startsWith(NODE_STRING);
    assertThat(throwable).hasMessageThat().contains(ERROR_ELEMENT_REMOVED);
  }