Jane Street Blog - What if writing tests was a joyful experience?

At Jane Street we use a pattern/library called “expect tests” that makes test-writing feel like a REPL session, or like exploratory programming in a Jupyter ...

At Jane Street we use a pattern/library called “expect tests” that makes test-writing feel like a REPL session, or like exploratory programming in a Jupyter notebook—with feedback cycles so fast and joyful that it feels almost tactile. Having used them for some time now this is the only way I’d ever want to write tests. Other languages call these “snapshot” tests—see for example Rust’s expect-test, which seems to have been inspired by our library, or Javascript’s Jest. We were first put onto the idea ourselves by Mercurial’s unified testing format, and so-called “cram” tests, for testing…

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• Kian Kasad
• Mukul A

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