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A small fuzzer finds regex bugs that example-based tests missed

matklad.github.io 12 min read Editor score 7/10

The author wrote a fuzzer to reproduce a known regex bug and found another bug in that version, while acknowledging the test was biased by knowing what to seek. It’s a useful, candid example of generative testing in practice.

What

Generative testing of Rust’s regex crate used generated patterns and input text, cross-checking regex against regex_lite.

How

The fuzzer found another bug in an older regex version: `.abb|b` on `zabb` returned `b` instead of `zabb`; the latest version showed no issue.

Why it matters

Cross-checking implementations supplies an oracle for algorithm tests, helping expose cases example-based tests may miss.

Read on matklad.github.io → Lobsters · 5 comments

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