assertNotNull(ArbitraryInstances.get(Type.class));
    assertNotNull(ArbitraryInstances.get(AnnotatedElement.class));
    assertNotNull(ArbitraryInstances.get(GenericDeclaration.class));
  }

  public void testGet_regex() {
    assertEquals(Pattern.compile("").pattern(), ArbitraryInstances.get(Pattern.class).pattern());
    assertEquals(0, ArbitraryInstances.get(MatchResult.class).groupCount());
  }