My dad in hindu, I fast secretly. Sometimes if he's home long enough that he'd notice, I break it, but the day before fasting I never know if that'll be the case so I go into the next day with intention to fast but breaking it if he's gonna notice, is my fast valid since you need full intention?

Ustadh AbdulAziz al-Haqqan

Full intention is a must akhi or the fast is invalid.