Question about entering Canada

Hi, all... I have a question about entering Canada from US.

I planned a 2 day driving trip from Detroit to Toronto around Christmas breaks. I am in OPT->H1b status right now, and should get H1b approvement in a couple of weeks. I called Maple immigration law office last week for the question of whether I should apply a visiting VISA to Canada? The answer was no. The attorney said what I only need to do is to bring the H1b approvement with me, and that's it. She even said when I driving into Canada, no one would ask for it. I would need to show the H1b approvement only if the officers ask for.

I am not sure if her is right. One of my friends told me that I must acquire the VISA before going to Canada. Do I have to? So confusing! Please help me if you know the answers of my questions.

I appreciate it.