public final void isNotSameInstanceAs(@Nullable Object unexpected) {
    if (actual == unexpected) {
      /*
       * We use actualCustomStringRepresentation() because it might be overridden to be better than
       * actual.toString()/unexpected.toString().
       */
      failWithoutActual(
          fact("expected not to be specific instance", actualCustomStringRepresentation()));
    }
  }
@Test
  public void isNotSameInstanceAsWithObjects() {
    Object a = new Object();
    Object b = new Object();
    assertThat(a).isNotSameInstanceAs(b);
  }