Regression Testing with Diffy

Your team has just finished a major refactor of a service and all your unit and integration tests pass. Nice work! But you are not done just yet. Now you need to make extra sure that you didn’t break anything and that there are not any lurking bugs that you have not caught yet. It’s time to put Diffy to work.

Diffy is an open source tool developed by Twitter to find potential bugs in software services. Unlike tools that ensure that your code is sound, like unit or integration tests, Diffy compares the behavior of your modified service by standing up instances of your new service and your old service side by side, routing example requests to each, comparing the responses and provides back any regressions that have surfaced from those comparisons.

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