When should I test?

Britney • I'm a happily married to the love of my life and I'm a 27 year old who is graduating university soon this year and is hoping to start having some beautiful babies soon! We have had one pregnancy and miscarriage at 7 weeks so far hoping for a rainbow baby
My af is supposed to be due in about four days but my other app says eight days when should I test? My first app is usually more right but I don't want to waste a test but also don't want to wait lol