UI Testing Essentials: Understanding Smoke and Sanity Testing

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In the dynamic world of software testing, Smoke and Sanity testing often stand out as two pivotal methodologies, guiding quality assurance teams to early defect identification. Both hold unique places in the testing lifecycle, offering distinct advantages and presenting specific challenges. In this article, we'll delve into these testing techniques, exploring their benefits and potential drawbacks to help your team gain maximum benefits from your testing efforts.

What is Smoke Testing?

Smoke testing concentrates on the most crucial aspects of your application. These are the early UI tests executed when a new build becomes available.

Purpose: Smoke Tests are quick, high-level tests to ensure that the most important parts of your application work. You're not digging deep, but you want to ensure that your basic features are operational. These tests evaluate the build's stability and determine if it is ready for further testing.

Let's understand it with an example. Let's say you want to write smoke tests for an e-commerce website like Amazon.

Sample Smoke Tests for an Amazon-like Website:

  • Can you open the homepage without any errors?
  • Can you search for a product?
  • Can you add a product to the cart?
  • Can you go to the checkout page?

Why is Smoke Testing important?

If any of these primary functionalities fail, there's no point in moving forward with more detailed testing because the basic user experience is broken.

So, you should run the Smoke tests early and quickly and communicate any issues or problems encountered to the developers ASAP. This allows your development team to resolve any issues promptly before your team invests time in testing the application further.

Smoke testing is a subset of acceptance testing. It is performed before any detailed functional or regression testing. Smoke Tests are run in the early phase of the software development lifecycle, often on builds that are not very stable. Sometimes, this type of testing is also called Build Acceptance testing.

To get the best results from your Smoke testing efforts, keep a few things in mind when designing and executing your tests:

1. Keep the tests focused on the most critical functionality of your application.

2. Schedule smoke tests early and often. Ideally, these tests should integrate with your CI pipelines to automatically run when a new build is ready.

3. Smoke tests should be completed quickly, offering developers prompt feedback so they can address the problems efficiently. Automate Smoke tests whenever possible to minimize the feedback time for developers.

Advantages of Smoke Testing

1. Catch major issues early: Smoke tests are designed to catch any big, show-stopping bugs early in the development cycle. These tests help identify and address any significant flaws before diving into detailed testing by ensuring that the primary functionalities are working.

2. Efficient use of QA time and resources: Smoke tests are typically run as soon as a new build is ready. This means that any fundamental flaw in the build can be detected immediately without wasting time on extensive testing.

3. Facilitates Continuous Integration: In modern development practices like Continuous Integration/Continuous Deployment (CI/CD), smoke tests play a pivotal role. Every time changes are integrated into the main branch; smoke tests can be triggered automatically, ensuring that the system remains stable with the new additions.

Disadvantages of Smoke Testing

  1. Surface Level Testing: Since smoke tests are designed to be broad in nature and cover only the main functionalities, they don't dive deep into the application. As a result, while they can identify major issues quickly, they might miss out on nuanced or intricate bugs that might be present in the system. Detailed and comprehensive tests will still be required after smoke tests to ensure the software's quality.
  2. Repetitive: If your team primarily relies on manual testing, running Smoke tests can be time-consuming and potentially frustrating, as stabilizing the build may involve multiple cycles of testing the same features repeatedly. This might not be the most efficient use of a QA's time.

The good news is that Smoke tests serve as an excellent starting point for automation. With fewer and generally simpler tests, they offer an excellent opportunity to evaluate and take advantage of the benefits of test automation for your team. We recommend utilizing test automation platforms such as Shaztra to address the issues associated with smoke testing.

What is Sanity Testing?

Sanity testing is a more focused form of testing of specific features. These tests serve as a targeted check post for any significant code alterations or deployments.

Purpose: Once you've determined that the main features work with the smoke test, sanity testing focuses on verifying that a specific section or functionality of the application works fine after recent changes.

Let's explore our example of an Amazon-like e-commerce website further. Let's say your developers just updated the 'Review' section of the product page. In Sanity testing, you won't test the entire application; instead, you'd focus solely on the 'Review' section of the product.

Sample Sanity Tests for the 'Review' section of an Amazon-like Website:

  • Can users submit a review?
  • Do star ratings appear correctly?
  • Can users see previous reviews?

and so on...

Why is Sanity Testing important?

Sanity testing helps confirm that recent changes or fixes in the application didn't unintentionally break related functionalities.

So, sanity tests are run whenever there is a need to ensure that specific changes or fixes to the software have not negatively impacted its immediate functionality. A few examples of such situations include:

After Bug Fixes: When a particular defect or issue has been resolved, you can run sanity tests to ensure that the fix works as intended and has not inadvertently affected other functionalities.

Before Releasing the Software: Before releasing the software to a wider audience or advancing it to the next phase, such as moving from staging to production, sanity tests can be performed to verify the functionality targeted by recent code changes.

After Build Deployment: When a new build is deployed, especially if it includes numerous changes, sanity tests are beneficial in confirming that the core features work as expected and that the build is stable enough for further, more comprehensive testing.

Sanity testing is a subset of regression testing. However, in Sanity testing, you are focusing only on the functionality related to the new changes and fixes introduced in the latest build rather than running the complete regression suite for your application.

Advantages of Sanity Testing

  1. Quick Feedback: Since sanity testing is focused on a specific functionality or a section, it can be executed quickly, giving immediate feedback to the development team. This helps in faster turnarounds when fixes or changes are needed.
  2. Resource-Efficient: Sanity testing doesn't require the comprehensive coverage that other testing types might need. This means fewer resources (time, personnel, and sometimes infrastructure) are used, making it cost-effective for your organization.
  3. Confirms Fix Integrity: When a defect is identified and fixed, sanity testing helps ensure the particular fix works as intended. It confirms that the recent changes have been implemented correctly and haven't adversely affected existing functionalities.

Disadvantages of Sanity Testing

  1. Limited Coverage: Since sanity testing is focused on a specific functionality or area, it doesn't provide a holistic view of the entire application or system. There's a risk that while the targeted functionality works perfectly, other areas of the application or integrations might have issues that go unnoticed during sanity testing.

However, leveraging test automation can help your team overcome the issues associated with Sanity testing. By running a complete automated regression test suite after sanity testing, you can ensure that all aspects of your application are thoroughly tested and meet your high-quality standards.


In essence:

  • Smoke Testing is your preliminary check. Think of it like ensuring your application's "engine" runs smoothly.
  • Sanity Testing is a focused check, ensuring that a recent "upgrade" or "repair" was done correctly without affecting its immediate surroundings.

Smoke testing and Sanity testing lay the foundation of your team's testing efforts. These tests identify problems early in the development process and guarantee that your users enjoy a seamless experience. Both types of testing establish the groundwork for a solid testing strategy and contribute to the overall quality of your application.