1. A method comprising: calculating, by a computer, churn metrics that indicate a degree of change between a first version of code and a second version of the code; calculating, by the computer for the second version, a historical variant metric feedback factor based on first metrics determined from the first version and on the second metrics determined from the second version and on the churn metrics; and performing, by the computer and based on the second metrics or on the churn metrics, a logistical regression resulting in a code failure proneness probability for the second version.