Smoke Testing in Software QA: A Complete Guide

Timothy Joseph
Timothy Joseph | February 24, 2023


The phrase “smoke test” was lifted from the construction industry. During this test, water pipelines would be filled with smoke to see if there were any leaks and other underlying issues.

In the tech industry, smoke tests were first used for hardware testing. In this test, hardware boards were tested to see whether they would smoke once they were plugged in and turned on. If they did emit smoke, they would fail the tests and were immediately unplugged. If they didn’t, they’d move on to the next round of testing.

Smoke testing plays a similar role in software development and quality assurance, albeit without the literal smoke.

What Is Smoke Testing in Software Testing?

It is a crucial part of developing applications and quality assurance. It is the first line of defense against faulty code in initial software builds. Smoke tests aren’t used to debug builds; they are used to find out whether the builds are working in the first place.

Unlike other QA tests that are exhaustive and check the overall code, smoke tests are fast and targeted. They are used to test new builds and ensure that the core or critical functions of the written program are working properly.

If any of the key features or functions of the software aren’t working, then the build is immediately rejected or redone. Testing only the main functionalities of the software helps save time, effort, and costs. In short, smoke tests can help improve your return on investment in the product.

After all, if there is an error with the critical areas of the build, it would be a waste of time to check its other, less important functions. It would also be a waste to continue working on the current build.


Features of Smoke Testing

It is also called build verification testing or build acceptance testing. The tests verify whether the main functions of the initial build are working accurately. Based on the results, the build may be accepted for the next series of QA tests or rejected altogether.

Smoke tests are sometimes also referred to as intake tests, as they decide the next round of testing.

There are several aspects involved in smoke testing. These aspects or features differentiate it from other types of QA tests.

Some of the key features of smoke testing are as follows:

  • Scope: A software system's important features and functionalities are the main focus of smoke testing. It tries to rapidly pinpoint significant problems or flaws that can obstruct future testing or production deployment.
  • Rapid Execution: Smoke tests are designed to be executed quickly, providing a high-level assessment of the application's stability and readiness for further testing. It helps in identifying showstopper issues early on.
  • Minimal Documentation: It does not require extensive documentation. It typically involves a predefined set of test cases or scenarios that cover the core functionalities of the application without going into detailed testing.
  • No Detailed Validation: It does not concentrate on completely validating each feature or scenario. It seeks to rapidly verify the application's overall stability and identify any major issues or failures that require immediate attention.
  • Focused on Stability: The main objective of this type of testing is to ensure the overall stability of the software. It helps identify critical defects that might prevent further testing or deployment.

When To Perform the Smoke Tests

Smoke tests are typically performed at specific points in the software development lifecycle to quickly assess whether a build or release is stable enough for further testing or deployment. Here are some common scenarios when you should perform smoke tests:

  • After Every Build: In a continuous integration (CI) or continuous delivery (CD) environment, smoke tests can be triggered automatically after each build. This ensures that basic functionality is intact before the build progresses to more extensive testing phases.
  • Before Integration Testing: Before integrating new code changes into the main codebase, performing smoke tests can catch any glaring issues early. This ensures that the integration process starts with a stable foundation.
  • Before Major Testing Phases: Before starting more comprehensive testing phases such as regression testing, user acceptance testing (UAT), or performance testing, it's a good practice to perform smoke tests. This prevents wasting time on tests if the build is fundamentally broken.
  • Before Manual Testing: If manual testers are involved, they can begin their testing efforts with a smoke test. This ensures that they are not spending time on deeper testing if the build is unstable.
  • Before Deploying to Staging or Pre-Production: Before promoting a build to staging or pre-production environments, conducting smoke tests helps verify that the build is stable enough for further testing by different teams.
  • Before Critical Releases: When preparing for critical releases or deployments to production, performing smoke tests is essential. It helps prevent major issues from reaching the production environment.
  • After Hotfixes or Emergency Changes: After applying hotfixes or emergency patches, running smoke tests can verify that the critical functionality affected by the changes is still working as expected.
  • After Environment Changes: If there have been significant changes to the underlying environment, such as infrastructure updates or configuration changes, running smoke tests can ensure that the application is functioning properly in the new environment.
  • After Code Merges: When code branches are merged, especially in version control systems like Git, running smoke tests on the merged codebase can identify any conflicts or issues introduced during the merge.
  • Before Demonstrations or Reviews: If you're preparing to showcase the application to stakeholders, clients, or during code reviews, conducting smoke tests ensures that the demo will not be marred by obvious bugs.

The timing of smoke tests depends on your development process, team structure, and the criticality of the application. Ideally, smoke tests should be automated and integrated into your CI/CD pipeline to provide rapid feedback and reduce the risk of faulty code moving forward in the development lifecycle.


How To Plan a Smoke Test

A smoke test may be manual, automated, or a mix of the two. Regardless of what type of smoke test you choose to conduct, the planning stage remains largely the same.

Here are some key tips for planning and running a smoke test:

  • Prepare for testing: Make sure to set the preferred atmosphere for the smoke test. This involves preparing any files, servers, and licenses you may need for the test. Create copies of your files and build as well, so you have backups in case anything happens.
  • Collect all necessary files: Get all the build or code files you will need for the test.
  • Write a test script: Use a single script to run the tests. Moreover, ensure that your script is written so that it creates and saves a report after each test. This way, any build failures can be properly and accurately reported to the developers.
  • Clean data: Ensure your test runs in a clean environment. Remove any extraneous files that may affect the smoke test. This also includes stopping the server and emptying database tables.

Types of Smoke Tests

There are three ways developers and QA engineers can conduct this type of testing. The type of smoke test used may depend on the builds you need to test, time constraints, or your personal preference.

  • Manual tests

    This is the most common type of testing. This method tests each initial build or any new features added to existing builds. In the manual method, you will have to modify or update your test scripts based on each test requirement. In some cases, you may need to create entirely new scripts.

  • Automated tests

    Automation smoke testing allows you to test batches of initial builds. Using an automation tool for this type of testing is ideal when you have limited time before build deployment.

  • Hybrid tests

    As their name suggests, hybrid tests are a mix of both manual and automated smoke tests. Combining the two types can boost the overall performance of the testing.


Smoke Test vs. Sanity Test

Sanity testing is a subset of regression testing. Its features are very similar to QA smoke testing, with one key difference.

Both tests are conducted quickly and efficiently. However, a smoke test is done on an entirely new build. A sanity test is done on an existing build with new features added or corrected functionalities.

Sanity tests are often performed on builds that have already passed the initial smoke tests. These builds are then modified or restored after a series of tests. As such, parts of the build are already stable, and only the new functionalities must undergo QA.

Smoke Testing Sanity Testing

Checks that critical functionalities or features of new builds are working acceptable

Checks for new functionalities added to existing builds or corrected bugs

Tests the basic end to end features of the system

Tests only a specific component in the system

Verifies the build or system stability before more rigorous testing

Verifies the rationality and originality of the system before more rigorous testing

A subset of acceptance testing

A subset of regression testing

Often documented and scripted

Not written and scripted

May be done on both stable and unstable builds

Only done on relatively stable builds or applications

Conducted by developers and testers

Conducted by testers or users


Advantages of Smoke Testing

  • Early Issue Detection

    QA Smoke tests are designed to catch critical issues early in the development cycle. By quickly verifying if the core functionalities of the application work as expected, smoke tests help identify major defects soon after changes are made, reducing the chances of these issues propagating further.

  • Quick Feedback

    Smoke tests provide immediate feedback to developers after code changes are made. This quick feedback loop accelerates the development process and allows developers to address issues before they become more complex and time-consuming to fix.

  • Reduced Regression Risk

    By ensuring that basic functionalities are intact, smoke tests help mitigate the risk of introducing regressions when new features or changes are added. This allows development teams to focus their efforts on more in-depth testing and innovation.

  • Integration Verification

    Smoke tests can be used to verify that different modules, components, or services of an application integrate correctly. This is particularly important in complex systems or microservices architectures.

  • Streamlined Development Pipeline

    Automated smoke tests can be seamlessly integrated into the continuous integration and continuous delivery (CI/CD) pipeline, automatically validating code changes and promoting a more efficient and reliable development process.

  • Faster Time-to-Market

    Detecting showstopper issues early prevents delays in the development process. With smoke tests, releases can be made with more confidence, leading to faster deployment and time-to-market for new features and updates.

  • Resource Efficiency

    Smoke tests save time and resources compared to running exhaustive test suites by focusing on the most critical functionalities. This is particularly beneficial during the initial stages of testing.

  • Quality Assurance

    Smoke tests contribute to the overall quality assurance process as a gatekeeper, ensuring that only stable and functional code moves forward in the development lifecycle.

  • Documentation of Basic Functionality

    Smoke tests serve as a form of documentation by outlining the essential features and behaviors expected to work consistently. This aids in maintaining a clear understanding of the application's core functions.

  • Support for Agile Practices

    In Agile development environments, where frequent iterations and changes occur, smoke tests align well with the Agile principles of continuous feedback, collaboration, and iterative development.

  • Risk Reduction in Production

    By catching major issues early, smoke tests help reduce the risk of deploying faulty code to production environments, enhancing the stability and reliability of the application.

  • Enhanced Communication

    Smoke tests provide a common ground for communication between development, testing, and business teams. The tests define a baseline of expected behavior that everyone can agree upon.


Tools For Smoke Testing

Here are some tools that were commonly used for writing smoke tests:

  • Selenium

    Selenium is a widely used tool for automating web browsers. It supports various programming languages like Java, Python, and C#. You can create smoke tests by automating interactions with web applications and verifying that critical functions are working as expected.

  • Cypress

    Cypress is a modern end-to-end testing framework specifically designed for web applications. It provides an easy-to-use API for writing smoke tests and other types of tests. Cypress offers real-time reloading, time-travel debugging, and an interactive test runner.

  • JUnit/TestNG

    These are popular testing frameworks for Java applications. They provide a way to write and execute tests, including smoke tests. You can create simple and quick smoke tests using these frameworks.

  • PyTest

    PyTest is a testing framework for Python applications. It's known for its simplicity and extensibility. You can write smoke tests using PyTest to ensure critical parts of your Python application are working.

  • Postman

    Postman is widely used for API testing. You can create smoke tests for your APIs by sending requests and verifying responses. Postman offers a user-friendly interface for constructing API calls and assertions.

  • Jest

    Jest is a JavaScript testing framework commonly used for testing JavaScript applications, particularly in the context of React applications. You can write smoke tests to ensure that components render and behave correctly.

  • SoapUI

    If you're dealing with web services and APIs, SoapUI is a tool that allows you to create and execute smoke tests for SOAP and RESTful APIs. It offers a range of testing features, including assertions and data-driven testing.

  • Robot Framework

    Robot Framework is a generic automation framework that supports both web and API testing. It uses a keyword-driven approach and supports multiple test libraries. You can use it to create smoke tests for various types of applications.

  • Gatling

    Gatling is a performance testing tool that can also be used to create smoke tests. It's particularly suited for testing the performance and load-handling capabilities of web applications.

  • Jenkins/Travis CI/CircleCI

    While not directly for writing smoke tests, these continuous integration (CI) tools can be used to automate the execution of your smoke tests as part of your development pipeline.

The "best" tool can vary based on your specific use case, programming language, and technology stack. Always evaluate the tool's features, community support, and compatibility with your project before making a choice.


Smoke Tests Trends

  • Shift-Left Testing and DevOps

    The trend of integrating testing earlier in the development process, often referred to as "shift-left" testing, was gaining momentum. This includes incorporating smoke tests as part of the development workflow to catch issues earlier and ensure faster feedback.

  • Microservices and API Testing

    With the rise of microservices architecture, the focus on API testing and smoke testing of individual services or microservices was increasing. Tools that supported API testing and integration testing were becoming more important.

  • Automation and Continuous Integration

    Automation was a persistent trend in testing, including smoke testing. Teams were adopting continuous integration (CI) practices and automating their smoke tests to ensure that quick feedback was available on code changes.

  • Containerization and Kubernetes

    As containerization and orchestration platforms like Kubernetes gained popularity, testing strategies needed to adapt. Smoke testing of containerized applications and their deployment pipelines became crucial.

  • Shift to Headless and Cross-Browser Testing

    With the increasing variety of devices and browsers, there was a trend towards headless testing (testing without a visible UI) and cross-browser testing to ensure the application worked seamlessly across different environments.

  • Focus on Performance and Security

    Smoke tests were also evolving to incorporate basic performance and security checks. Ensuring that the application could handle a minimal load and didn't have glaring security vulnerabilities became a part of smoke testing strategies.

  • AI and Test Automation

    The integration of AI and machine learning into testing tools was on the rise. This included using AI for test data generation, test case optimization, and even automated analysis of test results.

  • Non-Functional Testing

    While smoke testing primarily focuses on functional aspects, there was an increasing recognition of the importance of non-functional aspects like usability, accessibility, and user experience even in smoke testing.

  • Collaboration and Communication

    Teams were recognizing the importance of effective collaboration between developers, testers, and other stakeholders. Smoke tests were being designed to provide clear and concise feedback to the development team.

  • Cloud Testing Services

    Cloud-based testing services were gaining popularity, allowing teams to execute tests on a variety of platforms and environments without the need for extensive infrastructure setup.



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