Let’s talk about the differences between smoke testing, sanity testing, and user acceptance testing (UAT).

Generally, there is some confusion surrounding the topic of smoke testing vs. sanity testing. You might also be confused about why UAT is next to them. We want to clear it all out in this article.

Since all of them are considered quick checks, sometimes they can get mixed up, so let’s go over the basics. 

Smoke Testing or tester acceptance testing

It is a subset of acceptance testing executed before any detailed functional or regression tests are done. This software testing technique helps verify whether a deployed software build’s critical functionalities are stable.

The main objective of smoke testing is to verify that the important functionalities of the system are working as expected. That means we want to detect early major issues to avoid wasting time and resources in the future. 

In a nutshell, smoke testing is a simple test to show whether the product is ready for testing. Depending on your project’s goals, this can be done by either manual testing or by using an automation tool. 

Real-world Scenario

Imagine a newly deployed online banking system. A smoke test would confirm that users can log in, view their account balance, and log out. These are the most critical paths that the system should handle correctly before any further testing proceeds.

  • Early detection of major issues.
  • Less time and resources are spent on testing.
  • Minimal integration risk.

Smoke testing only verifies the most critical paths, potentially leaving out other important but less critical functionalities, meaning some bugs may go unnoticed.

Cost Considerations

Neglecting smoke testing can lead to expensive, time-consuming issues down the road. If the fundamental functionalities are flawed, then subsequent testing stages might face delays, adding to the total project cost.

Sanity Testing

It is a subset of regression testing. You perform sanity testing to ensure the code changes are working properly. More straightforward, sanity testing is executed after the software product has passed the smoke test. To learn more about creating a comprehensive sanity testing strategy, check out a related article on How to Create A Comprehensive Sanity Testing Strategy.

The main objective of sanity testing is to ensure the changes made are working as expected. 

Real-world Scenario

After updating an existing mobile app with a new feature that allows fingerprint login, sanity testing would confirm that this new feature works as intended without affecting existing functionalities like password-based login.

  • Quickly identify core issues.
  • No need for documentation.
  • Less time spent on regression testing.

You can do both smoke and sanity testing manually or with the help of an automation tool.


Sanity testing is narrow in scope and generally doesn’t cover edge cases or the interaction between the new feature and all existing features, which may lead to some issues being missed.

Cost Considerations

Sanity testing saves time and resources by focusing on specific features, but skipping it can lead to a broken feature going unnoticed, causing customer dissatisfaction and subsequent troubleshooting costs.

User Acceptance Testing (UAT)

It is the last phase of the software testing process. This type of testing is conducted after the product has undergone Unit, Integration, and System testing, and the end-user or the client executes it. 

The main objective of this type of testing is to ensure that the software product is ready for release. An effective UAT should be thorough and reflect the user requirements while identifying potential problems. 

Real-world Scenario

For an online grocery shopping platform, UAT would involve actual users trying to search for items, adding them to their cart, and completing the purchase. This ensures that not only are the requirements met, but the usability and user experience are up to the mark.

  • Keep ongoing maintenance costs as low as possible.
  • Reduces the risk of defects identified in production. 
  • Increase end-user happiness.


UAT can be time-consuming and is highly dependent on the users who are testing. If the user group is not representative or if they don’t thoroughly test all scenarios, issues may arise post-launch.

Cost Considerations

Cutting corners in UAT can be incredibly costly. Bugs found in production are not only more expensive to fix, but they can also damage your brand reputation and result in lost revenue.

To simplify it, we outlined the key differences between smoke, sanity, and user acceptance testing in the table below.

Smoke Testing Sanity Testing User Acceptance Testing (UAT)
It’s performed to check the critical functionalities of the build It’s performed to check the new functionalities or bugs that have been fixed  It’s performed at the end to check whether the software meets the customer’s requirements or not 
It’s performed by developers or testers Testers perform it It’s performed by the end user or the client 
Smoke Testing exercises the entire system from end to end  Sanity Testing exercises only the particular component of the system UAT exercises the system by using random inputs
It’s usually documented and scripted  It’s usually not documented and unscripted  It’s usually documented and scripted


To summarize, sanity and smoke testing are used to avoid wasting time and resources by quickly identifying whether the software build is too defective to start a rigorous testing process. 

In the industry, test cases for sanity testing are typically combined with those for smoke testing to speed up the test execution. As a result, the terms are often confused and used interchangeably. 

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