SASaser·May 21, 2026
I love Cram tests, they can be so readable! Being essentially shell scripts, though, they can be a bit hard to integrate into any given language's regular testing framework though.
I get the sense that "expect tests", also known as "inline snapshots tests", are becoming more and more popular. I think that many, including myself, first learned about it from the Jane Street blog post "What if writing tests was a joyful experience?" (https://blog.janestreet.com/the-joy-of-expect-tests/) because I keep seeing references to it. Indeed, the blog post points to Cram as prior art in this space. I also think Ian Henry's article "My Kind of REPL" (https://ianthehenry.com/posts/my-kind-of-repl/) makes a very convincing case for why expect tests are useful.
Jane Street has published their `ppx_expect` library for OCaml and you can use it today: https
Read the rest
://github.com/janestreet/ppx_expect. For other languages, here's an incomplete list of similar libraries I'm vaguely aware of:
- Rust: expect-test, (https://github.com/rust-analyzer/expect-test, quite old), insta (https://insta.rs/) and k9 (https://github.com/boujeepossum/k9)
- JavaScript: Jest has inline snapshot testing: https://jestjs.io/docs/snapshot-testing#inline-snapshots
- Python: inline-snapshot (https://15r10nk.github.io/inline-snapshot/latest/). Also discussed in this post from Pydantic: https://pydantic.dev/articles/inline-snapshot
- Go: https://github.com/hexops/autogold. I like it and use it daily at work. It has some shortcomings around working with strings as the expected value, so I'm fiddling with my own library that will be much more similar to `ppx_expect`.
- Zig: TigerBeetle has an internal `snaptest.zig` library in their codebase (https://github.com/tigerbeetle/tigerbeetle/blob/588123f219f1...), also discussed in their blog post "Snapshot Testing For The Masses" (https://tigerbeetle.com/blog/2024-05-14-snapshot-testing-for...).