MOmooreds·Oct 6, 2025Submission
Automated code reviews via mutation testing
28 points · Open discussionmbj
mutant
Ruby2014–2025
mbj / mutant
mutant
Mutation testing for Ruby. AI writes your code. AI writes your tests. But who tests the tests?
7Distinct people
7Mentions
0Explicit recommenders
2.2KGitHub stars
What to know before exploring
What it is
Mutation testing for Ruby. AI writes your code. AI writes your tests. But who tests the tests?
GitHub
Where it is used
No documented product use has been verified yet.
What people are saying
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Also in these discussions
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This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 3:03:16 PM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year7 dated mentions
Observed mentions: 2014-05-22 08:33:30 UTC to 2025-10-06 21:40:35 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2014 | 2014-01-01 00:00:00 UTC | 2015-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2015 | 2015-01-01 00:00:00 UTC | 2016-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2016 | 2016-01-01 00:00:00 UTC | 2017-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2017 | 2017-01-01 00:00:00 UTC | 2018-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 1 | 1 | 0 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 1 | 1 | 0 |
What Hacker News says
7 sourcesThere's a pretty good Ruby gem I've used for this before:
https://github.com/mbj/mutant
In An ex-Googler's guide to dev tools (2020)Mutant – Automated code reviews via mutation testing – semantic code coverage
2 points · Open discussionRuby, too: https://github.com/mbj/mutant I think most languages have something like this now.
In Things nobody told me about being a software engineerIf you're working with ruby mutant is pretty good -> https://github.com/mbj/mutant
In Java Mutation TestingIs this similar to Mutation Testing, where the code being tested is mutated, in order to identify unspecified behavior?
Mutant is a Ruby library for this: https://github.com/mbj/mutant
In Hypothesis 1.0: A property-based testing library for PythonIn the ruby world there is the "mutant" ( https://github.com/mbj/mutant ) gem that does stuff like this automatically.
It runs your tests and makes sure they all pass then it mutates the code under test (changing a == b to a != b or a <= 10 to a < 10) and makes sure that at least one of your tests fails.
If your tests still pass after the mutation then you know you are not covering something.
Tis a great idea but making a C version with the equivalent functionality would be a lot harder I think.
In C-Reduce, a C program reducer