pregnancy test accuracy if...

Hi there , I plan to take a pregnancy test tomorrow ... I'll only be 8-9dpo , not exactly sure which day I actually ovulated . I know it's early but I was having cramps and twinges and then I started to feel like I'm getting the flu but I haven't actually gotten sick so I thought I would test . Since it's pretty early I'm planning on doing it with first morning urine. When I wake up I can't hold my pee for the life of me ... I need to go immediately but will still need to run to the store to pick up the test as I don't get paid until tomorrow morning. So my question is , if I pee in a cup, immediately go to the store and back and then dip the test when I get back, will my urine still be good and the test will still be accurate ? I plan to cover the urine to prevent it from getting contaminated while I'm gone and I won't be longer than 20-30 minutes . I've read online that it should be okay but I'm looking for some personal experiences here .