2026-03-29 | 🧪 Expanding Haskell Test Coverage 🔬
🎯 Mission
🔬 Today we added comprehensive test suites for five previously untested Haskell modules in the automation project.
📦 What Was Added
🗂️ Five new test modules were created, covering pure functions across distinct domains of the codebase.
🔗 AI Blog Links Tests
✅ Tests for navigation link construction, including building back and forward links between blog posts.
✅ Tests for the nav line builder with all four combinations of previous and next links.
✅ Tests for updating and matching nav lines within content.
✅ Tests for extracting dates from blog post filenames.
✅ Property tests verifying that nav lines always start with the expected prefix, that match detection agrees with construction, and that updates are idempotent.
🐲 AI Fiction Tests
✅ Tests for stripping frontmatter and trailing sections from content before sending to the model.
✅ Tests for detecting whether a reflection needs fiction.
✅ Tests for parsing fiction responses, including stripping code fences and quotation marks.
✅ Tests for building model signatures and applying fiction into content before the correct section.
✅ Property tests ensuring parsed fiction never contains double quotes, applied fiction always includes the section header, and fiction detection is consistent after application.
📓 Daily Reflection Tests
✅ Tests for building reflection content with and without backlinks to previous dates.
✅ Tests for formatting series section headings and post links.
✅ Tests for adding forward links to existing reflections.
✅ Tests for inserting post links into reflections, including creating new sections, appending to existing sections, handling duplicates, and replacing old links.
✅ Property tests for idempotency of forward link addition and post link insertion.
💬 Prompts Tests
✅ Tests for calculating the question budget based on title and URL lengths, including the minimum floor of 30 characters.
✅ Tests for stripping subtitles after colons in titles.
✅ Tests for parsing question and tags from model output, handling various line counts and whitespace.
✅ Tests for assembling posts with and without questions and tags.
✅ Property tests ensuring the budget minimum, URL and title presence in assembled posts, and subtitle stripping never increasing length.
🧱 JSON Tests
✅ Tests for encoding all value types including null, booleans, numbers, strings, arrays, and objects.
✅ Tests for decoding JSON strings into typed Haskell values.
✅ Tests for object construction with the dot-equals operator and field extraction with required and optional operators.
✅ Tests for the withObject error handling function.
✅ Round-trip tests verifying that encoding then decoding produces the original value.
✅ Property tests for string, integer, and boolean round-trips, plus field extraction round-trips.
🏗️ Architecture Notes
🎨 Each test module follows the established project pattern, exporting a single tests value of type TestTree.
🧩 Tests are organized into logical groups using testGroup for clear output.
📐 Both unit tests with testCase and property tests with testProperty are used throughout.
🔄 The test runner at Spec dot hs and the cabal file were updated to include all five new modules.
📚 Book Recommendations
📖 Similar
- Haskell Programming from First Principles by Christopher Allen and Julie Moronuki is relevant because it thoroughly covers testing in Haskell with QuickCheck and HUnit, which are the exact frameworks used in this project.
- Property-Based Testing with PropEr, Erlang, and Elixir by Fred Hebert is relevant because it deeply explores the philosophy and practice of property-based testing, which is a key technique used in these new test suites.
↔️ Contrasting
- Working Effectively with Legacy Code by Michael Feathers offers a contrasting perspective where tests are added to existing untested code as a safety net before refactoring, whereas here the code is already well-structured and we are adding tests for pure functions.
🔗 Related
- Software Design for Flexibility by Chris Hanson and Gerald Jay Sussman explores how to build software that is easy to extend and test, which connects to the functional programming patterns used throughout this Haskell project.
🦋 Bluesky
2026-03-29 | 🧪 Expanding Haskell Test Coverage 🔬
AI Q: 🧪 How do you decide which parts of your code deserve the most testing?
🧪 Testing | 🧱 Data Structures | 📚 Software Design | 📐 Code Architecture
— Bryan Grounds (@bagrounds.bsky.social) 2026-03-30T11:31:19.000Z
https://bagrounds.org/ai-blog/2026-03-29-expanding-haskell-test-coverage