In short
Fixing one thing often breaks another. Regression testing re-checks what already worked, so last month's features don't quietly break with this week's change.
Re-testing previously working functionality to confirm a new change hasn't broken it — a discipline that becomes increasingly important, and increasingly automated, as an application grows.
Think of it like this
The plumber's surprise
The plumber fixes the leaking kitchen tap. That evening the bathroom geyser has no water pressure, because he touched a shared pipe. Checking the bathroom too, after a kitchen fix, is regression testing.
Watch it happen
A change in Coupon, a break in Pay
1/4A developer changes how coupons round the discount. Only the Coupon code was touched.
The big ideas
What you need to know
It grows every release
Each new feature adds tests to the suite. That's why regression is the first thing teams automate.
Choose by risk
When time is short, run tests for changed areas and anything sharing code with them first.
Every fixed bug gets a test
Add a regression test for each bug you fix so it can never quietly return.
See it in code
Walk through the code
1# Quick check on every build: only tests tagged @smoke2npx playwright test --grep @smoke3 4# Full safety net every night: tests tagged @regression5npx playwright test --grep @regression1/2--grep filters tests whose title contains @smoke. Fast feedback on each build.
Tag tests by suite in their titles, then run the right set at the right time.
Save yourself the pain
Common mistakes
Oops
Only retesting the exact bug that was fixed.
Do this instead
Also check features that share code or data with the change. That's where regressions appear.
Oops
Running the full manual regression suite every day by hand.
Do this instead
Automate stable, repetitive regression checks and spend human time on new and risky areas.
Your mission
Build a mini regression list
Quick check
Why is regression testing usually the first thing teams automate?
Go deeper
- 1Identify 5 critical workflows that should always be included in regression testing for a hypothetical app.
- 2Learn why regression test suites tend to grow over time and need periodic pruning.
- 3Understand why manual regression testing doesn't scale well, motivating Phase 7's automation.
More topics at this stop
Types of Testing (Functional, Non-Functional)
Black Box vs White Box vs Gray Box Testing
Test Case Design Techniques
Equivalence Partitioning & Boundary Value Analysis
Test Case Writing
Exploratory Testing
Smoke & Sanity Testing
Test Data Preparation
Bug Life Cycle
Writing Effective Bug Reports
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