Engineering Workflow

Finding Regressions with Binary Search

A regression appears in the current build, but the same behavior worked two weeks ago. Since then, the team has merged 80 changes. Reading all 80 diffs is possible, but it is slow and gives every change equal attention even though only one boundary in history matters: the point where the behavior changed from working to broken. When revisions are ordered and you can classify a revision reliably as good or bad, you can search that history with the same idea as binary search. Test a revision near the middle. Its result tells you which half can still contain the first bad revision. Repeat until only the transition remains.