Regression Testing vs Integration Testing: Key Differences
Here is a situation most backend teams have lived through. A developer changes how the user service formats dates. It is a tiny change: one line, a cleaner ISO format, every unit test still green. The pull request gets approved in five minutes. Two days later, the billing service starts failing to generate invoices, because it was still expecting the old date format from the user service. Two kinds of testing could have caught that, and they are the subject of this post.