@Test
public void testEquals() {

  new EqualsTester()
      .addEqualityGroup(new Set(), new Set(Collections.emptySet()))
      .addEqualityGroup(set, Set.of(ImmutableSet.of("string1", "string2")))
      .testEquals();
  java.util.Set<String> nullSet = null;
  assertNull(Set.of(nullSet));
}