A customer got angry will me when he past a night in darkness after I have finished my installation work. It happened that while working the main current supply breaker was off,and from when the work got finished the was no current for me to check the work up till closing hour. When the current latter came, unfortunately it was off working hours that I couldn't help. The customer got angry with me knowing that I have finished the work but still no light.Despite I was confident with the work done, I didn't asked him to switch on the breaker because it's off the ethics of the proffersion. So I asked him to be patient for I have to past the next day put on the breaker and do the checking.