Ruminating on Shadow Testing or Shadow Mirroring

Shadow testing is a software testing technique that involves sending production traffic to a duplicate or shadow environment. This allows testers to compare the behavior of the new feature in the shadow environment to the behavior of the old feature in the production environment. This can help to identify any potential problems with the new feature before it is released to all users.

The following diagram from the Microsoft GitHub site illustrates this concept.

The following blogs/articles explain this concept in good detail:

• https://microsoft.github.io/code-with-engineering-playbook/automated-testing/shadow-testing/
• https://github.com/opendiffy/diffy
• https://blog.markvincze.com/shadow-mirroring-with-envoy/
• https://reshadat.medium.com/test-apis-without-writing-tests-with-twitters-diffy-8dfad1d92b5