What if writing tests was a joyful experience?
Summary
Jane Street's blog post advocates expect tests, a snapshot-testing approach that lets tests resemble a REPL or Jupyter session, providing fast feedback and diffs to guide test creation. The piece argues this reduces test-writing toil, shows real examples across UI testing (Bonsai), low-level symbol demangling, and state-machine tests, and situates expect tests as a broader testing philosophy alongside property-based testing. It also covers the tooling around producing plain-text outputs via ppx_sexp_conv, and why the approach can improve maintainability and readability of tests.