Diagnosing Test Failures at Scale: Correlating Execution Evidence Across Ephemeral Runners

Intermittent test failures in a distributed CI/CD environment can slow down development and make failures harder to investigate. When an automated test suite fails on a local dev or staging machine, an engineer can view local logs, attach a debugger, or manually follow state changes. But when tests execute in a temporary container, AWS Lambda, or an agentless runner, post-mortem debugging is significantly more involved.

In a traditional setup, a failed build only shows a generic assertion error (504, ElementNotFoundException, etc.). An engineer may need to manually sift through CloudWatch log groups for an approximate timestamp, query Splunk, or reason about state changes across downstream microservices to understand why the test failed. Once the log retention period expires or if the execution did not have a shared, identifiable correlation ID, the engineer has no further information about the cause of the failure.