calledWith(f, s);
    }

    void check() {
      runTester();
      NullRejectingFromTo<?, ?> defaultFunction =
          (NullRejectingFromTo<?, ?>) getDefaultParameterValue(0);
      assertNotNull(defaultFunction);
      try {
        defaultFunction.apply(null);
        fail("Proxy Should have rejected null");
      } catch (NullPointerException expected) {
      }
    }
  }