Smoke Testing | A Key Tool for Identifying Software Issues

Discover a quick and easy way to test software functionality with smoke testing. Learn the basics of smoke testing and how it can help identify issues with software before further testing.

Kasper Siig
Kasper Siig
Cover Image for Smoke Testing | A Key Tool for Identifying Software Issues

Originating from hardware testing—where the term initially referred to the act of powering on a device to check for smoke emissions—the smoke testing process has become an essential part of modern software development, serving as a valuable tool for software developers, QA engineers, and tech decision-makers, saving both time and resources by identifying critical issues at an early stage.

In this post you’ll get an overview of the underlying principles of smoke testing, the various types, and their inherent benefits. On top of that, we aim to offer valuable insights into how smoke testing can be incorporated into your software development processes.

What is Smoke Testing?

Assessing the stability of a newly developed or modified software build is often the primary aim of smoke testing, focusing on key functionalities and verifying that they operate as intended. If the essential features aren’t functioning correctly—or if significant bugs remain unresolved—there is little rationale for continuing with more comprehensive testing.

Smoke testing is a non-exhaustive testing approach—meaning it does not cover all possible test cases—focusing on the most critical parts of a given application. Typically a smoke test suite is executed using expected scenarios and valid data, as it provides a somewhat reliable measure of the software's stability and readiness for further testing.

It’s crucial to understand that a somewhat reliable measure is perfectly acceptable for smoke tests, as it’s merely meant to avoid wasting time on the more comprehensive tests. For instance, smoke testing can be used to verify that a web app’s login functionality can be used by:

  • Navigating to the login page
  • Entering a valid username and password
  • Clicking the login button
  • Verifying that the user is redirected to the dashboard or home page

You can also think of smoke tests as “verification tests”.

In most applications, smoke testing is going to revolve around functional testing, however, some tools also allow you to perform smoke tests—and other related forms of testing—when it comes to non-functional testing.

It does, however, have its limitations. For example, the heavy reliance on expected scenarios and valid data means that it may not catch all possible issues, especially those that arise from negative testing or edge cases. Additionally, its non-exhaustive nature means that it is not a substitute for more thorough testing methods but rather a precursor to them. But, with that being said, that isn’t the goal of smoke tests in the first place.

Why Smoke Testing is Crucial in Software Development

The smoke testing process serves as a quality gate between different stages of the development pipeline, particularly after the generation of a new build. In DevOps, a smoke test suite is often the first set of automated tests executed, focusing on verifying the most critical parts of the application, allowing development and QA teams to proceed with confidence to more exhaustive testing and, eventually, to production.

Consider a cloud storage service that has recently integrated a new file-sharing feature. A well-designed smoke test could swiftly verify that users can still upload, download, and share files without encountering errors, thereby enabling quicker iterations and more reliable deployments.

It not only ensures that the most critical functionalities are intact but also aids in the early identification of significant issues, thereby facilitating more efficient and effective development processes.

Understanding the Different Forms of Smoke Testing

When diving into the world of smoke testing it’s important to understand the different types you might want to implement.

Manual Smoke Testing

Manual smoke testing allows testers to adapt to different testing conditions and requirements on the fly, which is particularly beneficial in projects where the requirements are not fully defined or where they’re subject to frequent changes.

This is on top of the nuanced evaluation capabilities that manual testing provides. Human testers can assess both the functionality and usability and user experience of an application. They can identify issues that automated tests might overlook, such as inconsistencies in the user interface or problems with the workflow that could affect the end-user experience.

Use-Case: Verifying a New Feature in a Mobile App

When a new feature is introduced in a mobile application, manual smoke testing can be used for initial validations. For example, if a mobile app introduces a new chat feature, manual testers can quickly ensure that the chat functionality works as expected without disrupting other features like notifications or user settings.

Moreover, manual testing allows for a nuanced evaluation of the new feature's impact on the overall user experience, as testers can validate the feature's ease of use, its integration into the existing user interface, and even whether certain design elements follow the brand’s design principles exactly, but somehow still look “off”. This ensures that the new feature not only works as intended but also aligns with the user experience goals of the application.

Use-Case: Checking Login Functionality After a Security Update

In the wake of a security update, manual smoke testing is essential for ensuring that core functionalities remain intact. For instance, if a security update aims to enhance password encryption, manual testers can verify that users can still log in using their existing credentials without encountering errors.

Testers can check for specific error messages, verify that two-factor authentication is functioning as expected, and even simulate various login scenarios to ensure that no new vulnerabilities have been introduced. Of course, this may also be possible with some automated testing tools, but it’s important to consider how much time you spent automating something versus how often it’s being done.

Is automation worth it?

At the end of the day, computers are essentially just incredibly intelligent babies. Their capabilities are astounding and incredible but you need to provide them with very specific instructions, which is where humans shine. This is of course without touching on the nuanced debate of AI in testing.

Automated Smoke Testing

When you do get to a point where you’re being limited by manual testing, automated smoke testing can be a highly efficient and capable way of running multiple test cases in parallel, thereby significantly reducing the time required for the testing phase. This is particularly advantageous in larger projects or in environments that prioritize speed, such as DevOps and Continuous Integration (CI) frameworks.

Also, automated tests can be easily scaled up to handle larger test suites, making it ideal for projects that grow in complexity over time. Moreover, once the initial setup is complete, automated tests can be run with minimal human intervention, thereby reducing the likelihood of human error and ensuring consistent test results.

However, as mentioned in the previous section, it’s important that the time saved by implementing automated tests outweigh the effort required to configure them. Because of this, it’s crucial to use a tool that requires as little configuration as possible.

Use-Case: Continuous Integration in a DevOps Pipeline

Automated smoke testing tools can be integrated into the CI/CD pipeline to automatically identify bugs. For example, after every code merge, you can run a series of tests to ensure that the changes haven't introduced any regressions or broken existing functionalities.

The advantage of this automated approach is its speed and efficiency. Because these tests are automated, they can be run in parallel, thereby providing quick feedback to the development team. This is particularly beneficial in a DevOps setting where continuous integration and rapid deployments are the norm.

Use-Case: Validating Multiple Builds in Parallel

Automated smoke testing shines in scenarios where multiple builds need to be validated simultaneously. For instance, if a software company is working on different versions of an application for various platforms, automated tests can validate all these builds in parallel.

Tools like Meticulous further enhance this efficiency by focusing on catching UI bugs without the need for writing or maintaining UI tests, drastically reducing the time to market and allowing development teams to concentrate more on feature development rather than late-stage bug fixing.

Screenshot of the Meticulous app showing some visual differences

Hybrid Smoke Testing

Hybrid smoke testing offers the best of both manual and automated testing, making it highly versatile. It allows teams to leverage automated tests for tasks that are repetitive and time-sensitive, while manual tests can be employed for tasks that require human judgment and contextual understanding.

The adaptability of hybrid testing is another significant advantage. It can be customized to fit the specific needs and constraints of a project, allowing for a more tailored testing strategy. For instance, in a complex project involving multiple microservices, automated tests can validate the interactions between services, while manual tests can focus on end-to-end scenarios and user experience.

Use-Case: E-commerce Platforms

In the context of e-commerce platforms, a hybrid approach offers a balanced testing strategy. Automated tests can swiftly validate database interactions and server logic, ensuring that the backend is robust. For example, automated tests can quickly verify that a new payment gateway integrates correctly with the existing system.

On the other hand, manual tests can focus on the user experience and visual elements, which are critical for customer engagement and satisfaction. Testers can manually navigate through the checkout process to ensure that it is intuitive and that all visual elements like buttons and banners display correctly.

Use-Case: Complex Applications Involving Multiple Microservices

For applications built on a microservices architecture, hybrid smoke testing is often the most effective approach. Automated tests can efficiently validate the interactions between different services. For instance, if a new microservice for user authentication is introduced, automated tests can ensure that it communicates correctly with the existing user database and other related services.

However, you may still want to get a human perspective of how the parts related to the user experience, in which case testers can manually verify that a new user authentication microservice works seamlessly from the user's perspective, ensuring that the login process is smooth and that all security protocols are followed.

Comparing Different Types of Smoke Testing

Understanding the nuances between different types of smoke testing—manual, automated, and hybrid—is crucial for making informed decisions in your software testing strategy. This section serves as a decision-making guide, focusing on two key criteria: speed and accuracy.

Speed as a Decision Factor

Imagine you're working against a tight deadline, and every minute counts. In such high-pressure scenarios, the speed of your testing process becomes a critical factor. Let's explore how each type of smoke testing process fares when speed is of the essence.

  • Manual Testing: While manual testing allows for targeted, in-depth testing, it is often time-consuming, especially for larger applications.
  • Automated Testing (Meticulous): Automated tests, particularly those run by tools like Meticulous, are exceptionally fast and can run multiple tests in parallel. However, the initial setup time can be significant.
  • Hybrid Testing: A hybrid approach offers a balanced speed, leveraging automated tests for quick validations and manual tests for more complex scenarios. The challenge here is coordinating between the two, which can sometimes lead to delays.

Accuracy as a Decision Factor

Now, picture a scenario where a minor bug could result in a significant security vulnerability. In cases like this, the accuracy of your testing process is non-negotiable. Here's how each testing method measures up in terms of accuracy.

  • Manual Testing: Offers a high level of accuracy for tests that require human judgment but is prone to human error in repetitive tasks, and is generally more time consuming over the course of an application’s lifetime.
  • Automated Testing: Highly accurate for automatable tasks like catching UI bugs. However, it may miss issues that require human intuition or business context understanding.
  • Hybrid Testing: Combines the accuracy of both automated and manual tests but requires careful management to avoid oversight.

Best Practices

  • For Speed: If you're in a race against time, and quick feedback loops are your lifeline, then automated testing stands as your most reliable ally.
  • For Accuracy: When the intricacies of human judgment come into play, and the stakes are high for even the smallest error, manual testing becomes the gold standard for accuracy.
  • Balanced Approach: For projects that require both speed and accuracy, a hybrid approach is often the most effective. It combines the rapidity of automated tests with the meticulous scrutiny of manual tests, offering a well-rounded testing strategy.

Choosing the right type of smoke testing is a nuanced decision that should be based on the specific needs and constraints of your project. Whether it's speed or accuracy that you prioritize, understanding the strengths and weaknesses of each type can guide you in optimizing your testing strategy.

When Should You Perform Smoke Testing?

The timing of smoke testing is a pivotal element that can substantially impact its efficacy. This section explores the optimal timing for creating and executing smoke test cases, segmented by the nature of the project: web development, mobile development, and DevOps environments. Although many more types of projects exists, these three will cover most scenarios that developers will experience.

Web Development

In the fast-paced world of web development, smoke testing emerges as an indispensable asset. It serves as an immediate validation checkpoint, confirming that new code integrations haven't adversely affected existing functionalities. This is especially vital in agile frameworks, where the ability to pivot quickly is a cornerstone of project success.

Mobile Development

For mobile application development, the timing of smoke testing is equally crucial. It's generally advisable to conduct smoke tests immediately after each new build to quickly validate essential features such as navigation, login, and data retrieval. This proactive approach ensures that the application remains both functional and user-friendly, which are key factors in retaining user engagement and satisfaction.

DevOps Environments

Within DevOps ecosystems, particularly those emphasizing continuous integration, the frequency of smoke testing should be synchronized with the rate of new code commits and integrations. This alignment guarantees that any emerging issues are promptly identified and addressed, thereby preserving the integrity and fluidity of the development pipeline.

The timing for conducting smoke tests is not a universal standard; it is contingent upon the specific project type and the development methodology in use. Whether you're engaged in web or mobile development, or navigating the complexities of a DevOps environment, discerning the ideal timing for smoke testing is essential. It plays a significant role in optimizing the test's effectiveness and, consequently, contributes to the overall success of your project.

Smoke Testing vs Other Types of Testing

Understanding the nuanced differences between smoke testing and other forms of testing—namely sanity and regression testing—is pivotal for crafting an effective testing strategy. This section aims to elucidate these distinctions by offering a criteria-based comparison, thereby enabling you to make informed decisions tailored to your project's unique requirements and challenges.

Objective: More Than Just Semantics

Each type of testing serves a unique objective. Smoke testing functions as a gatekeeper, ensuring that a new build is sufficiently stable and functional to merit more detailed testing. Sanity testing is akin to a surgical strike, focusing exclusively on specific functionalities or components that have recently been modified, while still not moving into full regression testing. Regression testing serves as a comprehensive safety net, ensuring that new code changes have not inadvertently affected existing functionalities.

Testing Type Objective
Smoke Testing Validates that new builds are stable and functional enough for further testing
Sanity Testing Focuses on specific functionalities or components that have undergone recent changes
Regression Testing Ensures that new code changes haven't disrupted existing functionalities

Scope: The Breadth of Examination

Smoke testing is a broad sweep, designed to cover essential functionalities and ensure the application's basic stability. Sanity testing narrows its focus to specific functionalities or components that have been altered. Regression testing is the most exhaustive, scrutinizing all areas of the application to ensure that even untouched segments remain unaffected by new changes.

Testing Type Scope
Smoke Testing Broad, covering essential functionalities
Sanity Testing Narrow, focusing on recently changed functionalities or components
Regression Testing Comprehensive, scrutinizing all areas of the application

Timing: When to Test?

Smoke testing is typically the first line of defense, performed immediately after a new build or major release. Sanity testing is more situational, coming into play after specific changes or bug fixes. Regression testing is a constant companion throughout the development cycle, especially following any code changes or updates.

Testing Type Timing
Smoke Testing Immediately after a new build or major release
Sanity Testing After specific changes or bug fixes
Regression Testing Constantly, especially after any code changes or updates

Depth: A Matter of Complexity

Smoke testing is quick and shallow, designed for early identification of high-level issues. Sanity testing, while also quick, delves deeper into specific functionalities to ensure they are working as intended. Regression testing is the most thorough, meticulously examining the application for unintended side-effects due to new code changes.

Testing Type Depth
Smoke Testing Quick and shallow
Sanity Testing Quick but deep into specific functionalities
Regression Testing Thorough and meticulous

Automating Smoke Testing: A Smart Move

In the ever-evolving landscape of software development, the need for efficient and reliable testing methods is paramount. Automated smoke testing has emerged as an indispensable tool, especially in environments that prioritize DevOps and continuous integration. But what sets it apart from manual methods?

A biased look at automated vs. manual testing can end up producing a comparison table like this:

Criteria Manual Testing Automated Testing
Speed Thorough but time-consuming. Can run in parallel, significantly reducing the time needed for testing.
Accuracy Susceptible to human error. Offers a higher degree of reliability, ensuring that the tests are performed the same way every time.
Reliability Limited by human fatigue and subject to inconsistency. Can be run as frequently as needed without fatigue, ensuring consistent results. Crucial for continuous integration pipelines.

It’s important to note that—as pointed out earlier—manual testing has its place in some organizations. However, with more and more tools becoming available with a focus on easing test automation, it’s becoming tougher and tougher to justify manual testing.

Also, automation in smoke testing is not just a technical upgrade; it's a business enabler.

Technical Advantages Business Benefits
Speed: Tests can run in parallel, reducing the overall testing time. Cost-Efficiency: Automated tests, once set up, can run without additional costs, making them cost-effective in the long run.
Reusability: Test scripts can be reused, ensuring consistency across different stages. Faster Time-to-Market: With quicker testing cycles, products can be released to the market more rapidly.
Accuracy: Eliminates human error, increasing the test's reliability.

Meticulous as a Benchmark for Automated Smoke Testing

Screenshot of the Meticulous app showing visual differences

Meticulous stands out as a popular tool for automated smoke testing, particularly for UI bug detection. It integrates seamlessly into CI/CD pipelines and offers unique features like replaying user traffic to catch UI bugs. Below is a sample configuration for integrating Meticulous into your CI/CD pipeline:

# Sample Configuration for Meticulous in a CI/CD pipeline
  - name: Run Meticulous Smoke Tests
    uses: meticulous-action@v1
      api_key: ${{ secrets.METICULOUS_API_KEY }}

The decision to automate smoke testing is not merely a technical one; it's a strategic choice that has far-reaching implications for both the quality and business aspects of a project. By understanding the comparative advantages and integrating tools like Meticulous, organizations can significantly enhance their testing efficiency and overall software quality.

Final Thoughts

Smoke testing stands as a cornerstone in the edifice of software quality assurance, serving multiple roles from gatekeeper to early-warning system. Its versatility is evident in its adaptability to various forms of testing—manual, automated, and hybrid—each with its unique set of advantages and limitations. The choice between these forms is not binary but rather a nuanced decision that should be tailored to the specific requirements and constraints of your project.

The timing of smoke tests is another pivotal factor that varies depending on the nature of the project and the development methodology in use. Whether you are engaged in web development, mobile application creation, or operating within a DevOps framework, the strategic timing of these tests can significantly influence their effectiveness.

Moreover, understanding the nuanced differences between smoke testing and other types of testing—such as sanity and regression testing—is indispensable for crafting a comprehensive and effective testing strategy. Each serves a unique purpose, scope, and depth, and understanding these can guide you in optimizing your overall testing approach.

Automated smoke tests, especially in fast-paced DevOps and CI/CD environments, is not just a technical decision but a strategic one. Tools like Meticulous offer a streamlined approach to automated testing, reducing both time and human error, thereby acting as significant business enablers. The initial investment in setting up automated tests is quickly offset by the gains in speed, reliability, and overall efficiency.

Final Recommendations

  1. Assess Your Needs: Before implementing any form of smoke testing, conduct a thorough assessment of your project’s specific needs, constraints, and objectives. This will guide you in choosing the most appropriate form of testing—manual, automated, or hybrid.
  2. Prioritize Timing: Align the timing of your smoke tests with your development cycle. Immediate testing after new builds or major releases can provide quick feedback, enabling timely corrections.
  3. Choose the Right Tools: If you opt for automated or hybrid testing, invest in reliable and user-friendly tools that require minimal setup but offer maximum efficiency. This not only speeds up the testing process but also ensures more accurate results.
  4. Continual Review: Given the dynamic nature of software development, it's crucial to continually review and update your testing strategies to adapt to new challenges and requirements.
  5. Integrate into CI/CD: If you are operating in a DevOps environment, integrate your automated smoke tests into your CI/CD pipeline for seamless and automated quality checks.

By implementing smoke testing in your software development processes, you not only ensure the quality and reliability of your product but also contribute to more efficient and effective development cycles. It is an investment in quality that pays rich dividends in both the short and long term.


Meticulous is a tool for software engineers to catch visual regressions in web applications without writing or maintaining UI tests.

Inject the Meticulous snippet onto production or staging and dev environments. This snippet records user sessions by collecting clickstream and network data. When you post a pull request, Meticulous selects a subset of recorded sessions which are relevant and simulates these against the frontend of your application. Meticulous takes screenshots at key points and detects any visual differences. It posts those diffs in a comment for you to inspect in a few seconds. Meticulous automatically updates the baseline images after you merge your PR. This eliminates the setup and maintenance burden of UI testing.

Meticulous isolates the frontend code by mocking out all network calls, using the previously recorded network responses. This means Meticulous never causes side effects and you don’t need a staging environment.

Learn more here.

Authored by Kasper Siig

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Kasper Siig
Kasper Siig

Kasper is a seasoned technical professional with experience ranging from DevOps engineering to specialized content creation, currently leveraging his deep understanding of technology to lead Siig Marketing, a firm dedicated to crafting high-converting, developer-focused marketing content.

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