How do I assert the result is an integer in PHPUnit? I would like to be able test that a result is an integer (1,2,3...) where the function could return any number, e.g.: $new_id = generate_id(); I had thought it would be something like: $this->assertInstanceOf('int', $new_id); But I get this error: Argument #1 of PHPUnit_Framework_Assert::assertInstanceOf() must be a class or interface name$thi..