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Shift-Left Testing: The Benefits of Early Stage Software Testing




‍Software development is an intricate process, often marked by unforeseen challenges and time-consuming troubleshooting. A common setback in many projects is the late discovery of bugs, which leads to costly and time-consuming corrections. To address this issue, Shift-Left Testing has emerged as a revolutionary approach. This dynamic strategy pushes the testing phase to the preliminary stages of the software development process, enabling early bug detection and enhancing code quality.

The Need for Shift-Left Testing

Historically, software testing was a phase that came late in the development lifecycle. This often resulted in critical bugs being discovered at the deployment stage, requiring extensive code patching and leading to project delays. The Shift-Left Testing strategy fundamentally shifts this paradigm, promoting frequent and early-stage testing. The results are impressive: fewer bugs, improved code quality, and a smoother deployment process.

The Traditional Software Development Process

In the traditional, sequential model of software development, testing typically occurred towards the end of the project. Stakeholders paid attention to detail and favored quality only at the later stages of the software development lifecycle. This approach often led to costly and time-consuming bug fixes, and in the worst-case scenarios, necessitated a complete redesign of the application.

The Shift-Left Movement

The Shift-Left movement advocates for moving the testing phase earlier in the software development lifecycle. The goal is to avoid the pitfalls of late-stage testing and instead introduce testing in the early stages of software development. The term ‘Shift-Left’ is derived from the fact that we read from left to right in most western languages, and thus, earlier phases of any sequence are represented on the left.

The Intersection of Shift-Left and Agile

Agile methodology emphasizes small code increments and includes testing as an integral part of the shorter development cycle. Therefore, Shift-Left Testing fits seamlessly into the Agile paradigm. After each code increment, often referred to as a sprint, testing is performed to verify the validity of the code.

Test-Driven Development (TDD)

Some organizations go a step further and push Shift-Left Testing even closer to the coding phase by adopting Test-Driven Development (TDD). TDD requires developers to first write the tests for the piece of code they plan to develop, enabling immediate verification of the code’s validity.

Use of Static Analysis Tools

Another way of pushing testing further left includes the use of static analysis tools. A static analysis tool helps identify problems with parameter types or incorrect usage of interfaces, thereby aiding in early-stage bug detection. ESLint, a well-known static code checker within the Node.js community, is one such tool that highlights coding mistakes in real-time.

Behavior-Driven Development (BDD)

Behavior-Driven Development (BDD) is another approach that can accelerate the Shift-Left movement. BDD defines a common design language that all stakeholders, such as product owners, testing engineers, and developers, can understand, enabling simultaneous work on the same product feature and improving team agility.

The Importance of Early Testing

Shifting testing to the early stages of the software development life cycle brings several benefits. Regularly testing code increment results in improved project quality and significant time and cost savings.

When are Most Bugs Introduced?

Approximately 85% of code defects are introduced during the coding phase. If an organization believes testing should only occur after the coding phase, many defects will be discovered during the testing phase, leading to a substantial amount of bugs that need to be fixed.

The Cost of Late Testing

The cost of identifying a bug varies depending on the stage of the software development lifecycle when the bug is discovered. On average, the cost is five to 10 times higher when finding a bug during system testing or even higher during the actual release of a product. The later a bug is found, the more expensive it is to fix, and the higher the likelihood of customer dissatisfaction.

The Benefits of Shift-Left Testing

Adopting a Shift-Left Testing strategy brings several benefits to software development processes. These include:

  • Early detection of bugs: By moving testing earlier in the software development lifecycle, bugs can be identified and addressed sooner.
  • Cost reduction: Detecting bugs early reduces the cost of bug fixes.
  • Improved product quality: The code contains fewer patches and fixes, leading to a higher quality product.
  • Time efficiency: The likelihood of overshooting the estimated timeline reduces.
  • Increased customer satisfaction: Stable code delivered within the budget results in higher customer satisfaction.
  • Maintaining a high-quality codebase: With fewer patches and fixes, the codebase remains high quality.

The Role of Test Automation in Shift Left Testing

Test automation plays a pivotal role in Shift-Left Testing. Given the frequency and early onset of tests, test automation tools can provide quicker feedback on the stability of new code, reducing the workload on the testing team and facilitating Shift-Left Testing. For instance, Testim offers a solution to record tests codelessly via UI interactions, accelerating the testing process.

Implementing Shift-Left Testing

If your organization is considering adopting Shift-Left Testing, the following steps can guide you through the process:

Agree on Coding Standards

Your development team needs to agree on the same coding standards. This ensures quicker code reviews and guarantees a higher quality of code, reducing the number of bugs.

Integrate Testing in Early Stages of Development

Select tools that are relevant for your codebase. Static code analyzers like ESLint can help detect bad coding practices and bugs during the development process. Consider adopting the Agile methodology, which works with small code increments, also known as sprints.

Embrace Test Automation

Frequent testing necessitates the adoption of test automation tools. Automating the running of tests for each code increment reduces pressure on the testing team and provides quicker feedback on the stability of the code. Test automation speeds up the development lifecycle, reduces time to market, and ensures fewer bugs are found later in the software development lifecycle.

The Impact of Shift-Left Testing

Implementing Shift-Left Testing can significantly transform your software development process. Here are some changes you’re likely to observe:

Reduced Waiting Time

Shift-Left Testing reduces waiting time related to testing activities. Traditional, non-agile settings see testers having to wait until developers finish implementing their features to commence testing activities. With Shift-Left Testing, testing becomes an early and frequent activity, reducing idle time for testers.

Increased Customer Involvement

Many Agile approaches state that customer involvement is essential for the success of a software project. Including customer involvement in your testing process can provide valuable insights and improve the overall quality of the software.

Adherence to the Testing Pyramid

The test automation pyramid is a concept in test automation that helps teams decide how to prioritize between different types of automated software tests. If your organization practices Shift-Left Testing, you’re likely to end up with more unit tests than any other type of test, meaning you’ll be following the testing pyramid.

Shift Left vs Shift Right Testing

Shift Right Testing is the practice of testing later in the development process, usually in production environments. While it may seem counterintuitive, Shift Left and Shift Right Testing are complementary. Shift Right Testing allows us to identify production issues before customers do, while the shorter feedback loops from Shift Left Testing give us the ability to respond to and remediate these production issues rapidly.

Is Shift-Left Testing the Future?

The decision to adopt Shift-Left Testing depends on your organization. Although every organization can theoretically move toward Shift-Left Testing, the benefits are clear. By detecting and reducing the number of bugs early in the software development lifecycle, we can ensure a higher quality of code and save time and money.

The Role of Agile Methodologies in Shift Left Testing

Adopting Agile methodologies can greatly enhance the effectiveness of Shift Left Testing. Agile practices enable faster and more frequent testing, allowing for early detection and correction of bugs. Using Agile methodologies in conjunction with Shift Left Testing can lead to significant improvements in software development processes and outcomes.

The Importance of Automated Testing in Shift Left Testing

Automated testing is a critical component of Shift Left Testing. Automation allows for more frequent and efficient testing, enabling bugs to be detected and fixed earlier in the development process. Implementing automated testing as part of your Shift Left Testing strategy can significantly reduce the time and resources required for bug fixes.


Shift-Left Testing is a transformative strategy that can significantly improve the efficiency and effectiveness of software development processes. By moving testing earlier in the development lifecycle, bugs can be detected and fixed sooner, reducing costs and improving the overall quality of the software. While implementing Shift-Left Testing requires a shift in mindset and practices, the benefits it brings to software development processes make it a worthwhile investment. As the software development industry continues to evolve, Shift-Left Testing stands as a powerful approach to enhance software quality and streamline the development process.







Mehdi Shokoohi

Software Quality Engineer

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