[be] a (dead|) cert

to be guaranteed or highly likely to occur or achieve success

After acing all the practice exams, she felt that passing the final test would be a cert.
Put your money on Thorpe to win, he’s a dead cert.
With his impressive qualifications and years of experience, getting the job seemed like a dead cert for him.
After months of preparation, her success in the competition became a dead cert.
With her impressive skills, it seemed like winning the competition would be a cert for her.