tasty-cache: Nix-style test caching for Haskell
tasty-cache is a Haskell library that enables selective test caching by skipping tests whose source code hasn't changed since the last passing run, using GHC HIE files for precise dependency tracking. It integrates with the Tasty testing framework and allows developers to wrap specific test groups with a cacheable flag for optimal performance. The tool is designed to work safely with pure tests while ensuring effectful tests run unconditionally.
- ▪tasty-cache uses GHC HIE files to track dependencies and determine whether a test should be re-run based on source changes.
- ▪Only tests explicitly wrapped with the cacheable function are subject to caching; others run every time.
- ▪The library requires GHC version 9.4 or higher and emits warnings or falls back to running all tests if HIE files are missing or unreadable.
- ▪It is distributed as a Nix flake with support for multiple GHC versions and integrates into Nix-based development workflows.
- ▪Tests involving side effects, network calls, or external state are intended to remain uncached for correctness and reliability.
Opening excerpt (first ~120 words) tap to expand
NoteThis project was built almost entirely with AI; see How this was built for the prompts. A human did, however, read over the readme and find it acceptable. tasty-cache A Tasty ingredient that skips tests whose source hasn't changed since the last passing run, using GHC HIE files for fine-grained dependency tracking. Quick start 1. Emit HIE files — add to both your library and test-suite stanzas in your .cabal file: library -- ... your other fields ... ghc-options: -fwrite-ide-info -hiedir .hie test-suite tests -- ... your other fields ... ghc-options: -fwrite-ide-info -hiedir .hie Both stanzas need these flags because the cache reads the HIE files for your library modules (to follow dependency chains) and your test module (to find the test body source). 2.
…
Excerpt limited to ~120 words for fair-use compliance. The full article is at GitHub.