NullPointerException e =
        assertThrows(NullPointerException.class, () -> tester.addEqualityGroup(1, null, 3));
    assertErrorMessage(e, "at index 1");
  }

  public void testSymmetryBroken() {
    EqualsTester tester =
        new EqualsTester().addEqualityGroup(named("foo").addPeers("bar"), named("bar"));
    try {
      tester.testEquals();
    } catch (AssertionFailedError e) {