Tagged mutation-testing

3 pieces

• August 30, 2026 · 6 min read

  Mutation Testing in Practice, Without It Taking All Night

  Naive full repo mutation runs the suite once per mutant and takes hours. Google's method makes it tractable at roughly two billion lines: mutate only changed covered lines, one mutant per line, suppress arid nodes, and surface survivors at code review rather than computing a score.

• August 26, 2026 · 5 min read

  Stop Chasing 100 Percent Mutation Score

  A mutation that produces behaviourally identical code can never be killed, so it inflates the surviving count and makes 100 percent unreachable. Prevalence runs 4 to 39 percent of all mutants. Google does not compute a classic mutation score at all, and optimises the usefulness of surfaced mutants instead.

• August 25, 2026 · 6 min read

  Do Injected Faults Track Real Bugs? The Case for Mutation Testing

  Across 357 real faults and 230,000 mutants, a coupling relationship held for 73 percent of real faults, and mutant detection tracked real fault detection more strongly than statement coverage did. The honest limit is that 17 percent of real faults couple to no mutant even in principle.