PHPUnit_Framework_Assert::assertNan PHP Method

    public static function assertNan($actual, $message = '')
    {
        static::assertThat($actual, static::isNan(), $message);
    }

 /**
  * Expect that a variable is nan.
  *
  * @param string $message
  *
  * @return Expect
  */
 public function toBeNan($message = '')
 {
     Assert::assertNan($this->value, $message);
     return $this;
 }