# Using acceptance tests to catch regression bugs in legacy code before production

DevFeed: [Using acceptance tests to catch regression bugs in legacy code before production](<https://devfeed.tech/articles/slow-releases-production-bugs-and-you-already-automated-31116.md>)

Original publisher: [Read original article](<https://journal.optivem.com/p/slow-releases-production-bugs>)

Author: Valentina Jemuović

Published: 2026-09-16T07:33:58Z

Content type: tutorial

Language: en

Sources: [Optivem Journal](<https://devfeed.tech/sources/optivem-journal.md>)

Topics: [Testing](<https://devfeed.tech/topics/testing.md>), [Requirements](<https://devfeed.tech/topics/requirements.md>), [legacy](<https://devfeed.tech/topics/legacy.md>)

Tags: [automated](<https://devfeed.tech/tags/automated.md>), [bugs](<https://devfeed.tech/tags/bugs.md>), [e2e](<https://devfeed.tech/tags/e2e.md>), [legacy-code](<https://devfeed.tech/tags/legacy-code.md>), [regression](<https://devfeed.tech/tags/regression.md>), [requirements](<https://devfeed.tech/tags/requirements.md>), [testing](<https://devfeed.tech/tags/testing.md>), [ui](<https://devfeed.tech/tags/ui.md>), [unit-tests](<https://devfeed.tech/tags/unit-tests.md>)

## AI overview

This hands-on article explains why automated unit and end-to-end tests may still allow production bugs in legacy code. It presents acceptance test-driven development (ATDD), where requirements and tests describe the same observable behavior, making coverage clearer and reducing dependence on UI steps.

## Source excerpt

You automated, and manual regression testing is still there. Those two facts have the same cause.