assertThrows(IllegalStateException.class, () -> checkState(false, FORMAT, 5));
    verifyComplexMessage(expected);
  }

  private static final String NON_NULL_STRING = "foo";

  public void testCheckNotNull_simple_success() {
    String result = checkNotNull(NON_NULL_STRING);
    assertSame(NON_NULL_STRING, result);
  }

  public void testCheckNotNull_simple_failure() {