Acceptance testing happens under time pressure, right before go-live, and every fix made during it carries a risk: it might break something that already worked. Re-testing everything by hand after each fix is impractical in that window. This is why automated regression testing during UAT and FAT is not just helpful — it is crucial and, in our view, mandatory.
The problem it solves
During UAT/FAT, defects are found and fixed rapidly. Each fix can have side effects elsewhere. Without automation, the team faces an impossible choice: re-test everything manually (too slow) or spot-check and hope (too risky). Automated regression removes that dilemma.
Automated regression inside the acceptance loop
Why it is mandatory
- Speed — the full suite re-runs in minutes, not days.
- Confidence — every fix is validated against all existing functionality.
- Protects the go-live date — no slow manual re-test bottleneck.
- Reliability — consistent, repeatable checks with no human fatigue.
Conclusion
Fixes during UAT and FAT always risk regressions, and manual re-testing cannot keep up under go-live pressure. Automated regression testing makes re-validation fast, reliable, and repeatable — which is why it is a crucial and mandatory part of modern acceptance testing.