how early to do a pregnant test?!

Kylie • Mum of 3 TTC #4 1st baby 2007 2nd baby 2009 3rd baby miscarried 4th baby rainbow baby 2012 chemical August 2016.
How early do u all wait to test? Do u wait till u missed period or do u try before?' How early can u test?! Wondering if I should take a test next week or not?!