In software testing, two terms often used interchangeably are Smoke Testing and Sanity Testing. While they seem similar, they serve different purposes and are used at different stages of the testing process.
Understanding the difference is essential for QA professionals to test smarter and communicate clearly with developers, leads, and stakeholders.
In this post, you’ll learn:
- What smoke testing is
- What sanity testing is
- Key differences between the two
- When and how to perform them
✅ What Is Smoke Testing?
Smoke Testing is a high-level, shallow test done to check whether the critical functionalities of an application work after a new build.
It’s also called a Build Verification Test (BVT).
🎯 Purpose: To check if the build is stable enough for further testing.
If the smoke test fails, QA rejects the build, and no further testing is performed until the issues are resolved.
🔍 Example:
You just received a new build for an e-commerce app. Smoke testing would include checking:
- Login works
- Homepage loads
- Product search returns results
- Add to cart is functional
You don’t go deep, just check if the major pieces are functioning.
🔁 What Is Sanity Testing?
Sanity Testing is a narrow, deep test performed after minor code changes or bug fixes to ensure the fixes work and haven’t broken related features.
It’s done after a regression build, usually when there’s no time for full regression testing.
🎯 Purpose: To verify that specific functionality is working after changes.
If the sanity test fails, QA rejects the specific fix or feature and sends it back to developers.
🔍 Example:
A bug was fixed in the checkout page. Sanity testing would focus on:
- Verifying the bug is actually fixed
- Ensuring payment still works
- Confirming totals are calculated correctly
You test only the affected module, but with full attention to detail.
📊 Smoke Testing vs. Sanity Testing – Comparison Table
| Feature | Smoke Testing | Sanity Testing |
|---|---|---|
| Purpose | Build verification | Quick validation of bug fixes or changes |
| Depth of testing | Shallow | Deep (on a narrow area) |
| Scope | Broad: covers major features | Narrow: focuses on specific functionality |
| Performed on | New build | Regression build or after code changes |
| Time to execute | Fast | Relatively fast, but deeper than smoke test |
| Test cases | Often scripted or automated | Often unscripted or exploratory |
| Decision after test | Accept/reject build | Accept/reject specific fixes or features |
🧪 When to Use Each Type
| Scenario | Type of Test |
|---|---|
| You get a new build from development | Smoke Testing |
| A bug is fixed in the login module | Sanity Testing |
| A major release is deployed | Smoke Testing |
| A hotfix is applied in production | Sanity Testing |
🛠 Best Practices
For Smoke Testing:
- Keep smoke tests lightweight and stable
- Automate them if possible for CI/CD pipelines
- Cover core user journeys (e.g., login, navigation, search)
For Sanity Testing:
- Focus on recently changed modules
- Don’t write full regression test cases—use exploratory judgment
- Prioritize tests that verify functionality and side effects
🧠 Final Thoughts
While both smoke testing and sanity testing are quick-check methods, they differ in scope, purpose, and timing.
Knowing when and how to use them helps QA teams:
- Save time
- Catch critical issues early
- Increase confidence in every build or fix
Clear communication on which test is being performed also helps developers and leads make better release decisions.
