{"slug": "mutants-at-the-mcg-6-00-pm-thurs-12th-of-november", "title": "Mutants at the MCG - 6:00 PM Thurs 12th of November", "summary": "Tristan Mc Leay will present \"Mutation Testing With Sydtest\" at the Melbourne Compose Group meetup on Thursday, 12 November, from 6:00 to 8:00 pm at Activity Room 2 of the Kathleen Syme Center in Carlton, with talks starting at 6:30 pm. The talk covers Sydtest's mutation testing framework for GHC, implemented as a GHC plugin with driver code, which checks test quality by asking whether changes to a line — swapping an operator, dropping a case, or hard-coding a boolean instead of an if or guard — would cause tests to fail. Mc Leay frames the technique as a way to keep AI code generation tools honest, applying it to a poorly covered codebase that was originally hand written but is now essentially agent-coded.", "body_md": "*Melbourne Compose Group is the monthly in-person meetup for functional programmers in Melbourne, which this month, is on the second Thursday of the month.*\n\n*Our November meeting will be 6:00-8:00 pm Thurs 12th of November at our regular venue, Activity Room 2 at Kathleen Syme Center in Carlton. Arrive from 5:30 for chat and socialising, talks start at 6:30pm. Please [RSVP via Luma](https://luma.com/i1j0ygwy).*\n\n**Tristan Mc Leay - Mutation Testing With Sydtest**\n\nNow that use of AI code generation tools has become prevalent, we need a way\n\nto keep our agents honest. Is our code well tested? Have we skipped tests?\n\nAre the tests sensible or meaningless? All of these could have been problems\n\nbefore AI, but they take on an increased significance when we can produce\n\nbigger changes than we might be able to genuinely concentrate on.\n\nMutation testing is a way of checking our test quality as well as our test\n\ncoverage: instead of just asking whether a line ran during testing, it asks\n\nwhether changes to that line would have caused the tests to fail. In the case\n\nof a typed functional language, that might be swapping an operator, dropping a\n\ncase, hard-coding a boolean instead of an if or a guard. If the tests continue\n\nto pass with a change in place, then the test suite is usually insufficiently\n\nsensitive to changes.\n\nSydtest includes a mutation testing framework for GHC, implemented as a GHC\n\nplugin alongside driver code. It was designed precisely for this problem - as\n\nour coding switches to AI, we need AI to look at our mutation test results to\n\nknow what to do next.\n\nIn this presentation, I will take a tour of Sydtest’s mutation testing and\n\napply it to a code base. This code base has poor test coverage and was originally hand written but nowadays is essentially agent-coded.\n\n*As always, newcomers welcome.*\n\n*Hope to see you there* \n\n*-Ben Hutchison & John Walker*\n\n \n1 Like\n\n \n[syd](https://discourse.haskell.org/u/syd)\n2\n \nHi! Syd here \n\nSuper cool to see someone discuss mutation testing!\n\nWill this be recorded? I’d like to see it", "url": "https://wpnews.pro/news/mutants-at-the-mcg-6-00-pm-thurs-12th-of-november", "canonical_source": "https://discourse.haskell.org/t/mutants-at-the-mcg-6-00-pm-thurs-12th-of-november/14906#post_2", "published_at": "2026-10-28 21:18:28+00:00", "updated_at": "2026-10-28 21:42:56.846011+00:00", "lang": "en", "topics": ["developer-tools", "ai-agents"], "entities": ["Melbourne Compose Group", "Tristan Mc Leay", "Sydtest", "GHC", "Kathleen Syme Center", "Ben Hutchison", "John Walker"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/mutants-at-the-mcg-6-00-pm-thurs-12th-of-november", "markdown": "https://wpnews.pro/news/mutants-at-the-mcg-6-00-pm-thurs-12th-of-november.md", "text": "https://wpnews.pro/news/mutants-at-the-mcg-6-00-pm-thurs-12th-of-november.txt", "jsonld": "https://wpnews.pro/news/mutants-at-the-mcg-6-00-pm-thurs-12th-of-november.jsonld"}}