Summary

Unified tests for Retryable Reads & Writes of the form "[command] succeeds after retryable handshake [error type]" intermittently fail the assertion on `ConnectionCheckoutStarted` events (expected 4x, got 3x) in multiple drivers (Node - NODE-6832, Python - PYTHON-5323, and Rust confirmed). We should investigate how to make these tests reliable.

Motivation

Who is the affected end user?

Driver devs

How does this affect the end user?

Flaky tests are distracting and can mask true failures.

How likely is it that this problem or use case will occur?

Very; e.g., weekly in Node

If the problem does occur, what are the consequences and how severe are they?

Time is wasted

Is this issue urgent?

No

Is this ticket required by a downstream team?

No

Is this ticket only for tests?

Yes

Acceptance Criteria

• Update the retryable reads and writes tests for retryable handshake errors to eliminate flakiness (as tested by the affected drivers: no occurrences in 1000x iterations after the fix)