Delta Debugging

Delta debugging is a technique used to determine the source of a particular software bug. It follows the scientific method: hypothesize, experiment, and refine. With delta debugging, we continually reduce the input that produces a bug until we reach a minimum amount of input required to trigger the bug.


We simplify our testing input to generate bugs for the following reasons:

  • Ease of communication
  • Easier debugging
  • Identification of duplicates

Simplification techniques

The first technique discussed in this lecture is the use of a binary search to remove input until the crash-producing input is identified.

Delta debugging algorithm

Delta debugging is similar to a binary search, however, when it fails to find a bug it increases the granularity of the changes or deltas that it tests. Deltas are blocks of input being used to test a target program. The delta debugging algorithm continues to try different subsets of deltas until it encounters a bug. The bug producing input is retained and the deltas increase in granularity until no bugs can be triggered.