Delta Debugging is a technique to simplify and isolate failure-inducing changes. Its most popular application is onprogram inputs,where it reduces a failure-inducing input to a minimal input that still triggers the failure. This paper provides a retrospective on Delta Debugging, discussing its origins, applications, and impact. We also discuss the limitations of Delta Debugging and suggest directions for future research.

Given some test case, a program fails. Which circumstances of the test case are responsible for the particular failure? The delta debugging algorithm generalizes and simplifies the failing test case to a minimal test case that still produces the failure. It also isolates the difference between a passing and a failing test case. In a case study, the Mozilla Web browser crashed after 95 user actions. Our prototype implementation automatically simplified the input to three relevant user actions. Likewise, it simplified 896 lines of HTML to the single line that caused the failure. The case study required 139 automated test runs or 35 minutes on a 500 MHz PC.

Given some test case, a program fails. Which part of the test case is responsible for the particular failure? We show how our delta debugging algorithm generalizes and simplifies some failing input to a minimal test case that produces the failure. In a case study, the Mozilla web browser crashed after 95 user actions. Our prototype implementation automatically simplified the input to 3 relevant user actions. Likewise, it simplified 896 lines of HTML to the single line that caused the failure. The case study required 139 automated test runs, or 35 minutes on a 500 MHz PC. Categories and Subject Descriptors D.2.5 [Software Engineering]: Testing and Debugging---debug- ging aids, diagnostics, testing tools, tracing General Terms Automated debugging, combinatorial testing 1. INTRODUCTION Often people who encounter a bug spend a lot of time investigating which changes to the input file will make the bug go away and which changes will not affect it. --- Richard Stallman, Using and Port...