Verification-first development (VFD) prioritizes writing formal specifications and proofs before writing implementation code. This approach, while seemingly counterintuitive, aims to clarify requirements and design upfront, leading to more robust and correct software. By starting with a rigorous specification, developers gain a deeper understanding of the problem and potential edge cases. Subsequently, the code becomes a mere exercise in fulfilling the already-proven specification, akin to filling in the blanks. While potentially requiring more upfront investment, VFD ultimately reduces debugging time and leads to higher quality code by catching errors early in the development process, before they become costly to fix.
Matt Keeter describes how an aesthetically pleasing test suite, visualized as colorful 2D and 3D renders, drives development and debugging of his implicit CAD system. He emphasizes the psychological benefit of attractive tests, arguing they encourage more frequent and thorough testing. By visually confirming expected behavior and quickly pinpointing failures through color-coded deviations, the tests guide implementation and accelerate the iterative design process. This approach has proven invaluable in tackling complex geometry problems, allowing him to confidently refactor and extend his system while ensuring correctness.
HN commenters largely praised the author's approach to test-driven development and the resulting elegance of the code. Several appreciated the focus on geometric intuition and visualization, finding the interactive, visual tests particularly compelling. Some pointed out the potential benefits of this approach for education, suggesting it could make learning geometry more engaging. A few questioned the scalability and maintainability of such a system for larger projects, while others noted the inherent limitations of relying solely on visual tests. One commenter suggested exploring formal verification methods like TLA+ to complement the visual approach. There was also a brief discussion on the choice of Python and its suitability for such computationally intensive tasks.
Summary of Comments ( 17 )
https://news.ycombinator.com/item?id=43402102
Hacker News users discussed the practicality and benefits of verification-first development (VFD). Some commenters questioned its applicability beyond simple examples, expressing skepticism about its effectiveness in complex, real-world projects. Others highlighted potential drawbacks like the added time investment for writing specifications and the difficulty of verifying emergent behavior. However, several users defended VFD, arguing that the upfront effort pays off through reduced debugging time and improved code quality, particularly when dealing with complex logic. Some suggested integrating VFD gradually, starting with critical components, while others mentioned tools and languages specifically designed to support this approach, like TLA+ and Idris. A key point of discussion revolved around finding the right balance between formal verification and traditional testing.
The Hacker News post titled "Verification-First Development" (linking to an article on buttondown.com) generated a moderate amount of discussion, with a number of commenters sharing their experiences and perspectives on the topic.
Several commenters affirmed the value of thinking about verification early in the development process, even if not strictly adhering to a "verification-first" methodology. One user highlighted how focusing on testability from the outset often leads to simpler and more modular designs. They emphasized that while full formal verification might not always be practical, the mindset of considering how to verify functionality early on is beneficial.
Another commenter pointed out the connection between verification-first development and test-driven development (TDD). They argued that TDD, when done correctly, inherently involves thinking about verification before implementation. The act of writing tests first forces developers to define the expected behavior of the code, which is a crucial step in the verification process.
There was some discussion about the tools and techniques used in verification-first development. One commenter specifically mentioned TLA+, a formal specification language, and its usefulness in designing robust systems. They shared a personal anecdote about using TLA+ to catch subtle errors early in the design phase, preventing significant debugging effort later.
A few commenters expressed skepticism about the practicality of verification-first development for all projects. They acknowledged its potential benefits for complex systems, but questioned its suitability for simpler applications where the overhead of formal verification might outweigh the advantages. They suggested that a more pragmatic approach would be to adopt a risk-based strategy, applying more rigorous verification techniques only to critical parts of the system.
Some comments also touched on the challenges of applying verification-first development in practice. One user mentioned the difficulty of accurately specifying the desired behavior of a system, especially in complex domains. They noted that incomplete or incorrect specifications can lead to false confidence in the correctness of the implementation. Another challenge mentioned was the learning curve associated with formal verification tools and techniques, which can be a barrier to adoption for some developers.
Finally, a couple of commenters shared links to related resources, including articles and talks on formal methods and software verification. This suggests a broader interest in the topic within the Hacker News community.