UAT vs Regression Testing: What’s the Difference and When to Use Each

Every software team runs into the same question: What is the difference between UAT and regression testing?

Many people think they are the same because both happen near the end of a project. They are not.

• Regression testing checks that new code did not break old features.
• User Acceptance Testing (UAT) checks that the software actually does what the business needs¹.

Understanding UAT vs regression testing helps QA engineers, developers, project managers, and business users release better software with fewer surprises.

What Is Regression Testing?

Regression testing means you run old tests again to make sure nothing that used to work is now broken.

Think of it like this: You fixed a flat tire on your car, but you still drive around the block to be sure the other three tires are okay. That quick drive is regression testing.

Key Points About Regression Testing

• Done by QA team or automated tools
• Looks only at existing features
• Happens every time code changes
• Usually automated so it can run fast and often
• Runs before anyone from the business starts testing

What Is User Acceptance Testing (UAT)?

User Acceptance Testing is the final check done by real business users or customers.

They try the software the way they will use it every day and say, “Yes, this works for me” or “No, this is not what we asked for.”

Think of it like a test drive before you buy a new car. The customer drives it, not the mechanic.

Key Points About UAT

• Done by business people, product owners, or real end users
• Tests complete business processes (end-to-end flows)
• Based on acceptance criteria written at the start of the project
• Almost always manual
• Ends with an official sign-off (yes, we accept this)

UAT vs Regression Testing – Easy Comparison Table

The Correct Order: Regression First, Then UAT

Correct order in every project (Waterfall or Agile):

1. Developers finish new code
2. QA runs regression testing → build must be stable
3. Only then do business users start UAT

Never send a shaky build to business users. They will waste hours finding bugs that regression testing should have caught — just like getting spam calls when your number is exposed online. Learn how to protect your phone number online the same way you protect your build with regression.

Who Should Do What?

• Regression testing → QA engineers (and automation scripts)
• User Acceptance Testing → People who will actually use or pay for the software

Tip: QA cannot do real UAT. They know the system too well and do not think like a normal user — just like you can’t spot every scam call unless you know what to look for. Check spotting and reporting phone scams to stay safe online and in testing.

Simple Examples

Regression Testing Example

Old feature: User can log in

New change: Added “Forgot password” button

Regression test: Try normal login → still works? Good!

UAT Example

Business rule: A manager must approve an expense in under 5 clicks

UAT test: Real manager logs in, finds expense, approves it → Did it take 5 clicks or fewer? Does email go out? All good²?

Best Practices Everyone Should Follow

For Regression Testing

• Automate as many tests as you can
• Run the most important tests every night
• Connect tests to your CI/CD pipeline
• Keep your test data clean — just like keeping unknown callers out of your phone. Use virtual phone numbers in test environments to avoid real user data leaks.

For UAT

• Write clear acceptance criteria from day one
• Give business testers real-looking data
• Keep the UAT environment exactly like production
• Always get written sign-off³

Common Mistakes That Waste Time and Money

• Starting UAT before regression passes
• Skipping automation “to save time” (ends up costing more)
• Letting QA write UAT scripts — they are too technical
• Treating UAT feedback as optional

4 Most Asked Questions About UAT vs Regression Testing

Does regression testing come before UAT in Agile?

Yes – always. In every sprint, automated regression runs first. Only a green regression build goes to business users for UAT.

What is the difference between UAT and regression testing?

Regression checks technical stability (“nothing broke”). UAT checks business fitness (“does it do what we paid for?”).

Who performs UAT and who performs regression testing?

Regression → QA team + automation

UAT → business stakeholders, product owners, or real end users.

Can UAT ever be automated?

Very rarely. Some teams automate data setup or simple happy-path checks, but real UAT is manual because only humans can judge if something “feels right” for the business.

Final Words: Master UAT vs Regression Testing for Smooth Releases

UAT vs regression testing are best friends, not rivals.

Regression testing keeps the software technically healthy.

User Acceptance Testing makes sure it is useful in the real world.

Run regression first, automate it, keep the build stable, then invite your business users for UAT. Do this and your releases will be smoother, faster, and much less stressful — just like knowing who is really calling from 1-408-521-9478 or any unknown number.

What is the biggest mix-up you’ve seen between regression and UAT in your team? Drop it in the comments – let’s learn together!

References & Further Reading

1. Quora – Which comes first: Regression or UAT? → https://www.quora.com/Which-testing-comes-first-Regression-or-UAT ↩︎
2. Stack Overflow – Unit, Integration, Regression, Acceptance → https://stackoverflow.com/questions/7672511/what-is-the-difference-between-unit-integration-regression-and-acceptance-test ↩︎
3. TechTarget – Testing types explained → https://www.techtarget.com/searchsoftwarequality/answer/The-difference-between-functional-testing-and-regression-testing ↩︎