baking Soda pregnancy test?!

I'm 5 days late for my period and I've taken two .88 cent tests from wal mart they both were negative but I'm never late. So my friends mom told me about how back in the day they used to put baking soda in one cup and pee in another and once you pour the urine in if the baking soda foams you're pregnant... mine foamed. I'm obviously skeptic so my friend who knows she's not pregnant did it and hers did not foam... opinions please! lol I know this is weird but whatever