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Concerning Quality
Personal blog · concerningquality.comprogrammingsystems
Concerning Quality is a personal blog at concerningquality.com about programming and systems. Since 2021, 9 different Hacker News readers have linked it 28 times, most often “Branch Coverage Won't Prove the Collatz Conjecture”. It is still writing: the last post was on 2026-05-01, and you can follow it by feed.
Too few sampled comments (4) to say how often HN recommends it.?
Why HN links it
HN commenters link this blog for posts on model-based testing, formal verification and functional semantics, mainly in the context of testing business applications against simple models of behaviour.
Summarised by Claude from a sample of 4 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- Branch Coverage Won't Prove the Collatz Conjecture3 people · 3 mentions · first linked 2025-01-27
- Property-Based Testing Against a Model of a Web Application2 people · 4 mentions · first linked 2022-08-11
- Simulating Some Queues2 people · 2 mentions · first linked 2025-01-06
- Compiling a Test Suite2 people · 2 mentions · first linked 2023-08-23
- State Space Explosion: The Reason We Can Never Test Software to Perfection(2021)2 people · 2 mentions · first linked 2022-08-23
- Logical Time and Deterministic Execution2 people · 2 mentions · first linked 2023-03-01
What Hacker News says?
There's a lot of assertions that I throw into business applications that would be very useful to test in this way. So I don't think this only applies to testing databases. Also, when properties are difficult to think of, that often means that a model of the behavior might be more appropriate to test against, e.g. https://concerningquality.com/model-based-testing/ . It would take a bit of design work to get this to p…
Comment linking /model-based-testing/
on “Is something bugging you?”Submitted Does your test suite account for weak transaction isolation? as a story · 86 points
HN discussionCompare the spec with the application here: https://concerningquality.com/model-based-testing/ I think we've become used to the complexity in typical web applications, but there's a difference between familiar and simple (simple vs. easy, as it were). The behavior of most business software can be very simply expressed using simple data structures (sets, lists, maps) and simple logic. No matter how much we simply it,…
Comment linking /model-based-testing/
on “AI will make formal verification go mainstream”Submitted State Space Explosion: The Reason We Can Never Test Software to Perfection(2021) as a story · 10 points
HN discussionFor "business applications," I much prefer the variant of property testing called model-based testing. This is where your property is "does the implementation behave like some simplified model." This is the correct way to test such applications in my opinion, because users don't care about "custom widgets," "queues," or "databases." They care about business functionality, which is quite easily expressible in model f…
Comment linking /model-based-testing/
on “Property-Based Testing for the People”Submitted Bug Bash 2025 conference writeup as a story · 5 points
HN discussionI've come to the conclusion that executability and reasoning are separate axes. If we view everything in terms of languages with interpreters, of course functional semantics must be executed by imperative machines. But to reason about either kind of program, we need functional semantics, because functional programming is the language of pure reasoning. More on the subject: https://concerningquality.com/quality-and-p…
Comment linking /quality-and-paradigm/
on “Functional semantics in imperative clothing”Submitted Extracting a Verified Interpreter from Isabelle/HOL as a story · 4 points
HN discussionSubmitted The Verification Gap: A Major Hurdle for the Industry Adoption of Formal Methods as a story · 4 points
HN discussionSubmitted Simulating Some Queues as a story · 3 points
HN discussionSubmitted Efficient and Flexible Model-Based Testing as a story · 3 points
HN discussionSubmitted Domain-Driven Test Data Generation: A Category-Partition Method and Property-Ba as a story · 3 points
HN discussionSubmitted State Space Explosion: The Reason We Can Never Test Software to Perfection (202 as a story · 3 points
HN discussionSubmitted Property-Based Testing Against a Model of a Web Application as a story · 3 points
HN discussionSubmitted Branch Coverage Won't Prove the Collatz Conjecture as a story · 2 points
HN discussionSubmitted The Case for Models as a story · 2 points
HN discussionSubmitted Refinement: Formalizing the Simplicity Underneath Complex Programs as a story · 2 points
HN discussionSubmitted Bug Bash 2: Attack of the Clones as a story · 1 points
HN discussionSubmitted Branch Coverage Won't Prove the Collatz Conjecture as a story · 1 points
HN discussionSubmitted Branch Coverage Won't Prove the Collatz Conjecture as a story · 1 points
HN discussionSubmitted Simulating Some Queues as a story · 1 points
HN discussionSubmitted Controlling Nondeterminism in Model-Based Tests with Prophecy Variables as a story · 1 points
HN discussionSubmitted Forward and Backward Reasoning in Proof Assistants as a story · 1 points
HN discussionSubmitted Compiling a Test Suite as a story · 1 points
HN discussionSubmitted Compiling a Test Suite as a story · 1 points
HN discussionSubmitted Most Tests Should Be Generated as a story · 1 points
HN discussionSubmitted Logical Time and Deterministic Execution as a story · 1 points
HN discussionSubmitted Logical Time and Deterministic Execution as a story · 1 points
HN discussion