PHPUnit_Framework_Assert::isJson PHP Method

    public static function isJson()
    {
        return new PHPUnit_Framework_Constraint_IsJson();
    }

 public function toBeJson()
 {
     if ($this->negate) {
         a::assertThat($this->actual, a::logicalAnd(a::isType('string'), a::logicalNot(a::isJson())));
     } else {
         a::assertJson($this->actual);
     }
 }