Smoke and sanity testing are two of the most common software testing methodologies. While “sanity testing” is often mistakenly used as a synonym for “smoke testing,” the two focus on different aspects. Understanding their key differences is important to avoid confusion.
Smoke testing involves verifying that the key functionalities of an application still work after a new build. In contrast, sanity testing is more focused, checking that specific changes made to an already validated build work as expected.
In this smoke vs sanity article, you will learn what smoke and sanity testing are, how they work, when to use them, and whether they can be effectively combined.
Let’s dive in!
What Is Smoke Testing?
Smoke testing, also called “confidence testing,” “build promotion testing,” or “build verification testing,” is a type of software testing aimed at varying that critical system functionalities work as expected after a new build.
It aims to identify major issues and determine whether the build is stable enough for further testing. As explained in Lessons Learned in Software Testing by Cem Kaner, James Bach, and Brett Pettichord: “The phrase smoke test comes from electronic hardware testing. You plug in a new board and turn on the power. If you see smoke coming from the board, turn off the power. You don’t have to do any more testing.”
The practice gained popularity with the advent of Agile development methodologies, where frequent builds are a priority. Smoke testing ensures stability early in the development lifecycle, helping teams decide whether to continue the deployment.
How to Apply Smoke Testing
At its core, smoke testing follows a straightforward process:
Everything starts with the development of a new feature, update, or an entirely new version of the software. Once the development is complete, a new software build is produced and typically sent to a CI/CD pipeline for deployment.
Next, smoke tests are executed. These tests are a selected subset of test cases — including unit tests, E2E tests, API tests, and more. Their goal is to test the most important functionality of the system, ensuring that core features are still working as intended.
If the smoke tests pass, the deployment process continues with more specific testing phases, such as regression or integration tests. On the contrary, if the smoke tests fail, the deployment is halted. The build is rejected and sent back to the development team to address the identified issues. Once fixed, a new build is created, and the cycle repeats until the software passes the smoke testing phase.
In other words, smoke testing is a critical checkpoint in software development. It acts as the first line of defense to ensure that new builds are stable and ready for deployment. This is particularly effective in an automated testing pipeline, as it helps teams quickly understand whether to proceed with deployment or stop it immediately, saving time and resources.
Example of a Smoke Test Scenario
Imagine an e-commerce platform where a new payment gateway integration has been added to the checkout process. The development team has modified the application to include that new gateway, which allows customers to choose between multiple payment methods.
The key functionalities that should be verified, regardless of the changes made in an e-commerce application, include:
- Login and sign-up workflow: Ensure that users are still able to log in and create new accounts.
- Cart and checkout workflow: Users still need to be able to add items to the cart, proceed to checkout, and fill in necessary details such as shipping address.
- Payment methods: Check that all payment options are available and function correctly.
- Order confirmation: Ensure that after payment — regardless of the chosen payment method — the order is processed and the user receives a confirmation of the successful purchase.
These smoke tests confirm whether the e-commerce application still works correctly after the new build.
Smoke Testing Frameworks and Tools
There are no dedicated tools or frameworks designed specifically for smoke testing. Since every software application is unique, the choice of tools depends on the specific functionalities you need to verify in your smoke tests.
For example, in one application, the key functionalities might involve API endpoints, while in another, it could focus on ensuring that the login workflow functions correctly. For testing API endpoints, tools like Postman or Swagger are highly effective. If your smoke tests target core business logic, unit testing frameworks such as JUnit, Jest, or Mocha are well-suited. On the other hand, when smoke testing involves verifying complete user workflows, tools like Playwright, Cypress, or Selenium are ideal choices.
Ultimately, smoke testing is less about the tools themselves and more about the strategy — selecting the appropriate tests to efficiently verify the build’s stability.
Pros and Cons of Smoke Testing
Let’s discover the main advantages and disadvantages of smoke testing!
👍 Pros:
- Early detection of critical issues
- Can be run frequently and quickly, as it generally involves only a limited subset of test cases
- Improves build quality
- Can be integrated into CI/CD pipelines for testing automation
- Enhances team productivity by saving time thanks to its shift-left approach to testing
👎 Cons:
- Identifying the right smoke tests requires skills and can be time-consuming, especially in larger projects
- Passing smoke tests can create an illusion of stability, as deeper issues may exist in the application
- Requires a lot of maintenance as the smoke testing suite needs regular updates to reflect changes in core functionality
Wonderful! Time to continue this smoke testing vs sanity testing comparison by exploring sanity testing.
What Is Sanity Testing?
Sanity testing, also known as “surface level testing,” is a type of software testing aimed at verifying that specific functionalities or bug fixes in a software build are working as expected. It focuses on checking that minor changes to the application have not introduced unintended issues or caused core features to break.
Sanity testing is a narrow and quick check to confirm that the software is stable enough for more comprehensive testing. In most cases, it is performed after smoke testing.
How to Apply Sanity Testing
The cycle of sanity testing is similar to that of smoke testing. The main difference is that it starts from a more stable build that has already passed smoke testing, rather than from a new build that has yet to be tested.
The main goal of this testing process is to validate changes made to one or a few specific parts of the application. It is a targeted approach that focuses on specific components to ensure they are functioning properly after changes.
Sanity tests perform a quick and superficial check to confirm that the system still works as expected after a modification. Due to its focused and narrow scope, sanity testing tends to be carried out manually by software engineers or QA experts and is often not automated.
Example of a Sanity Test Scenario
Consider again the example of an e-commerce application where the development team has introduced a new payment gateway. After the application has passed smoke testing, sanity tests would focus solely on the feature that has changed — the payment system.
Testers will ensure that all payment methods work as intended, thoroughly validating these features to confirm that the new payment gateway integration functions correctly without affecting other parts of the application.
Sanity Testing Frameworks and Tools
In most cases, sanity testing does not require dedicated frameworks, as it is achieved manually and without scripts. However, in cases where a more robust and/or automated sanity testing process is needed, the same considerations applied to smoke tests also apply to sanity tests.
Pros and Cons of Sanity Testing
Let’s see the main benefits and drawbacks of sanity testing!
👍 Pros:
- Cost-effective, as it is simple and not structured
- Narrow and quick, with focused verification on areas of the application that have changed
- Increases confidence in the robustness of a given build
👎 Cons:
- May require manual effort, as it may not be easily automated
- Effectiveness depends on the tester’s ability (at this exact moment) to accurately identify issues
Can Smoke Tests and Sanity Tests Coexist?
TL;DR: Yes, smoke and sanity tests can be used together.
Sanity and smoke tests can coexist in a software development cycle, as they serve distinct but complementary purposes:
Smoke testing is the first step, verifying that core functionalities are working after a new build. Once smoke testing is successful, builds become more stable, and sanity testing is carried out. That focuses on specific changes to ensure those updates did not introduce new issues and bugs.
While both testing approaches can be used together, they are typically applied in different scenarios. Smoke testing is often automated and integrated into CI/CD pipelines, while sanity testing is generally done manually. In a typical process, smoke tests can be automated, and once they pass, manual sanity tests are performed on the changed features to confirm they work as expected.
If you prefer a fully automated approach, you may rely solely on smoke testing or invest in creating automated sanity tests. At the same time, automating sanity tests can be time-consuming and may not justify the effort, as these tests are extremely specific and hard to re-use.
Smoke vs Sanity Testing: Summary Table
Explore the differences between the two approaches to testing in the smoke vs sanity comparison table below:
AspectSmoke TestingSanity TestingPurposeVerify that the core functionalities of an application are still workingCheck that bugs have been resolved and the introduced changes are functioning as expectedGoalEnsures the build is stable enough for further testingEnsures an application works after changes or fixes to proceed or not with further testingWhen performedOn a new buildOn a new already validated build, usually after smoke testingTest ExecutionAutomated or manuallyTypically performed manuallyExecuted throughA subset of automated test scriptsUsually, manually by testers, developers, or QA expertsCoverageCovers core functionalitiesFocuses on specific modules where changes were madeType of testsUnit, E2E, integration, etc. (based on the key features of an application)Depends on the changes to testFrameworks and toolsCI/CD tools (Jenkins, CircleCI, Semaphore), API testing (Postman, REST Assured), UI testing (Selenium, Cypress, Playwright), unit testing (JUnit, Jest), custom test automation frameworks, and moreManual testing tools (TestRail, Zephyr), bug tracking (Jira, Bugzilla), exploratory testing tools, development IDEs for quick verification, and more
Conclusion
In this smoke vs sanity testing comparison guide, you learned about the differences between the two. While they are often confused and sanity testing is sometimes seen as the same as smoke testing, they are actually distinct methodologies. Both share a similar testing loop, but they are applied at different stages of the development lifecycle.
Originally published at https://semaphoreci.com on January 28, 2025.
