Sanity Testing vs. Smoke Testing

The world of software development is ever-evolving, and software testing is indispensable to ensure robust, stable, reliable, and high-performing software. Testing professionals use various testing strategies and techniques across the software development life cycle (SDLC). Among the vital testing techniques used in the early phases of software testing are sanity testing and smoke testing.

These two techniques serve different purposes and are applied at various stages in the testing process. However, they are often confused due to their apparent similarities and overlapping objectives. While smoke testing and sanity testing are both initial testing methods, smoke testing verifies the basic functionality of the new build. In contrast, sanity testing verifies recent changes made to the application to rule out any defects.

Let us delve deeper to understand the meaning of smoke and sanity testing. This article also explores the difference between smoke and sanity testing and explains each technique’s practical use cases and importance.

What is Sanity Testing?

Sanity testing in software testing checks that the specific components or functionalities of a software application are working as expected after changes or fixes. Think of sanity testing as a form of regression testing that verifies the correctness of specific functionality or a feature after a minor change or a bug fix.

Key Objectives

Key objectives of sanity testing are as follows:

• It is targeted and not exhaustive like regression testing.
• To quickly verify that the specific functionality or feature affected by the change is working as expected.
• To verify that the changes made to the software have not introduced any imminent new bugs or issues in the specific component or functionality.
• To ensure the logical correctness of operations after changes.

Timing and Scope

Sanity testing is performed after a stable build obtained as a result of minor changes passes the smoke test. It focuses only on the specific area that has changed and ensures the application’s stability and rationality are intact after the changes.

Sanity testing, primarily exploratory or manual, deals with the working and correctness of specific application parts.

Example

If the login page of an application had a bug where password validation failed, a sanity test would:

• Check the password validation bug fix.
• Ensure login works as intended.
• Validate any related functionality affected by the fix, like session management.

Thus, a sanity test would test and verify only related functionality and not the entire application.

Benefits and Limitations

The benefits and limitations of sanity testing are shown in the following table:

What is Smoke Testing?

Smoke testing, also known as build verification testing, confidence testing, or initial checkout, is a testing technique that checks whether the primary functionality of the application is working as expected. Smoke testing is performed after the new build of the application is available, and it ensures that the application is functioning correctly and stable enough for further testing.

Note: The smoke test gets its name from hardware testing, where a device is said to be passed if it doesn’t emit smoke on its first power-up.

Using smoke testing, the application’s basic functionality is checked by giving it a quick, shallow check to verify that the application has no critical defects and the build is stable. Testers or developers perform smoke testing before any detailed testing is performed.

Key Objectives

Some of the key objectives of smoke testing are:

• It is performed to verify that the critical functionalities of the application are working after a new build.
• It determines whether the build is stable enough for further, more detailed testing.
• As a result of the smoke test, severely broken, unstable builds are directly rejected. This saves time and effort.

Timing and Scope

Smoke testing is performed early in the development cycle, after a new build is ready. It is a broad, high-level check of core features of the application performed to ensure that the new build is ready for further testing. This technique catches the defects early on and prevents further testing on unstable builds. It acts like a gatekeeper; if the build passes the smoke test, it proceeds to more detailed testing, such as functional, regression, or integration testing. Otherwise, the build is rejected. Read more about how smoke testing differs from regression testing: Smoke Testing and Regression Testing – the Differences Between

Example

For example, consider a login application. A smoke test would check:

• Whether the application launches.
• If the login form is displayed, and the input fields accept values.
• If clicking the login button sends a request, and a valid login redirects to the dashboard.

If any of these steps fail, the testing is halted and the build is rejected. If all steps pass, the build is passed for detailed testing.

Benefits and Limitations

The following are the benefits and limitations of smoke testing:

Smoke Testing vs. Sanity Testing: Key Differences

The following table provides the detailed differences between smoke and sanity testing:

Smoke testing ensures the entire build is generally stable and key functionalities work. Sanity testing takes it a step further and focuses on those specific changes that were made to see if they are working fine.

Sanity and Smoke Testing in a CI/CD Pipeline

Software undergoes continuous and rapid changes in a modern Continuous Integration/Continuous Deployment (CI/CD) environment. Sanity and smoke testing ensure faster feedback and improved quality. Explained below is how both techniques fit in:

Smoke Testing in CI/CD

In a CI/CD environment, smoke testing:

• Quickly identifies broken, unstable builds.
• Rejects bad builds right away and prevents unnecessary regression runs on these bad builds.
• Integrates seamlessly with build tools and automated test suites to provide quick results.

Sanity Testing in CI/CD

Sanity testing performs the following tasks in a CI/CD environment:

• Validates bug fixes and minor changes without running complete regression suites.
• Detect side effects, if any, for small changes made.
• Carries out rapid cycles of fix-and-verify.

Smoke and sanity testing are critical “fail-fast” mechanisms that ensure higher confidence in deployments and prevent wasted effort.

Practical Use Cases and Scenarios

Here are some scenarios for smoke and sanity testing techniques.

Scenario 1: New Build Deployment

• Action: Deploy a new version of the application.
• Testing: Smoke test execution.
• Outcome: The build is either accepted for further testing or rejected because it is unstable.

Scenario 2: Bug Fix in Checkout Process

• Action: Fix a bug causing incorrect tax calculation.
• Testing: Run a sanity test focused on tax computation.
• Outcome: The bug fix was validated before moving to complete regression.

Scenario 3: New Feature in Application

• Action: Add a new feature like “dark mode”.
• Testing:
  • Smoke test: Ensure the new build is stable and the app loads and menus are rendered.
  • Sanity test: Verify the dark mode toggle and related UI components.
• Outcome: The new feature added is validated.

Best Practices for Smoke and Sanity Testing

For the success of smoke and sanity testing, some best practices should be followed.

Best Practices for Smoke Testing

• Maintain a set of test cases that are critical yet minimal.
• Automate smoke tests using intelligent tools like testRigor.
• Integrate with CI/CD pipeline.
• Use tagging to differentiate smoke tests from complete regression tests.

Best Practices for Sanity Testing

• Document bug fixes and minor changes clearly.
• Design sanity test cases that only target affected areas.
• Maintain historical records of previous sanity tests.
• Understand the change scope by communicating closely with developers.

Automation Tools for Smoke and Sanity Tests

Automating test cases using test automation tools make it easier to include smoke and sanity tests in the SDLC. Although, sanity tests are mostly conducted manually, automating them using advanced test automation tools can save lot of testing time.

Some of the popular tools for automating smoke and sanity tests are:

• testRigor: This is a no-code automation tool that supports fast authoring of smoke and sanity tests.
• Selenium: Is an open-source tool for automated browser testing.
• JUnit/TestNG: These are the frameworks for writing unit and integration smoke tests in Java.
• Jenkins/GitHub Actions: These CI tools can trigger smoke and sanity tests automatically.

Automating smoke and sanity tests significantly reduces regression cycles and ensures consistent quality in fast-paced release environments.

Conclusion

Smoke testing and sanity testing are the techniques that are foundational to a mature software quality assurance strategy. Although they seem to be similar in terms of scope and speed, their application differs significantly. Smoke testing verifies the suitability of a build, while sanity testing verifies the accuracy of a specific functionality after changes are made.

Embracing both smoke and sanity testing allows software teams to deliver high-quality software faster with confidence. Both these testing techniques contribute to shorter feedback loops, more resilient software systems, and better collaboration between developers and testers.

Use them as proactive tools to maintain high standards and deliver customer value at high speed.