Datafetcher – Host by Jane Street

Monday, September 11
5:00 pm - 6:30 pm

Building 34, room 401 - Grier Room

Presented by: James Yu

Writing automated tests for real-world code often involves tediously mocking out dependencies—a problem made more difficult if you haven’t designed your code for testability in the first place. Datafetcher is a library at Jane Street that tries to solve this problem for a large class of programs that fetch and process data. While requiring you to make almost no code changes, it equips your program with a cleanly factored test harness and allows you to mint tests automatically by recording and replaying production requests. Meanwhile, it gives you caching and query batching for free.

In this talk, we’ll show Datafetcher in action and explain how its design evolved, exploring the powerful OCaml features that made it possible.

Food and swag will be provided. Let us know if you plan on coming! Registration is not required to attend but will help us make sure we have enough food and swag.


  • Date: Monday, September 11
  • Time: 5:00 pm - 6:30 pm
  • Location: Building 34, room 401 - Grier Room