Coined by Larry Smith in 2001, Shift-left testing is defined as a transformative software testing technique that emphasizes integrating testing throughout the entire software development lifecycle. For some, it’s simply another industry buzzword pushed by technical marketers. 

In theory, shift-left testing sounds great, but what does it really mean? Is it just another Agile buzzword, or can it genuinely enhance software quality? In this article, we'll explain what shift-left is, what it means for developers and testers, and how to implement it into your team. 

In the early 2000s, the SDLC was largely approached in a sequential, or Waterfall way, where development and testing were carried out in different phases.  Shift-left on the other hand, entails testing at the end of a sprint or release at each stage of the development process. Rather than waiting until the end of a sprint to test, QA and developers work together from the start to build testable code and test requirements as soon as possible.

Let’s have a look at how testing in traditional linear SDLC looks versus how it looks in the agile shift-left testing approach.

Shift-left testing is a continuous practice that requires a collaborative approach between the development and QA teams. 

Let’s break down the concept of shift-left testing for different roles. 

As a developer, the shift-left approach encourages you to prioritize testability and quality right from the start, rather than focusing solely on the speed of delivery. It's all about thinking ahead and considering scalability, security, and user experience with each new feature you build. 

In other words, shift-left encourages a broader perspective among developers. It's not just about writing code that works; it's also about understanding how that code fits into the larger system, how easy it will be to maintain in the future, and how vulnerable it might be to security breaches. So, by embracing shift-left, you're not only ensuring functionality but also considering the bigger picture. The key is recognizing that writing code is only part of the job—you also need to think about how that code will function long-term. Shift-left means working to build it right the first time.

For QA testers, shift-left means working hand in hand with developers to conduct unit, integration, and system tests as new features are being built. During the requirements-gathering stage of the SDLC, you collaborate with developers to define acceptance criteria and spot any potential issues before any code is written. After that, you do test planning where you work with developers to figure out the overall test strategy and plan specific test cases needed for development testing.

By the time the development phase is finished, you and the stakeholders ensure that the product meets all the requirements and is ready for release by conducting user acceptance testing (UAT).

Shift-left testing for QA testers results in higher quality product releases and fewer bugs making it into production. Your input as a QA professional helps developers build code of higher quality, reducing wasted effort caused by defects discovered later on.

When done right, shift-left can save a lot of money and time. Here are several benefits of shift-left testing that everyone can appreciate:

Improved Software Quality: By testing requirements and use cases upfront, you build quality into your code from the start. Shift-left helps you meet customer needs and ensure a good user experience. You gain insight into how people will really use your software, enabling you to optimize performance and head off accessibility issues. As a result, you are guaranteed a more stable and reliable final product.

Faster Development Cycles: Shift-left testing can actually accelerate development. It helps you uncover and fix bugs early on hence avoiding the need for extensive debugging later, ultimately saving time.

Reduced Costs: The earlier a bug is detected, the less time wasted rewriting code and the lower the cost to fix it. According to research by the Systems Sciences Institute at IBM, the cost to fix a bug found post-deployment is four to five times as much as one uncovered during staging phases, and up to 100 times more if identified during the maintenance phase.

In fact, did you know test data can help you uncover many meaningful insights to prevent costly defects and bugs, application crashes, and even downtime?

Shift-left testing works by starting testing at the requirements phase, not waiting for development to end. Testers and developers work together to review requirements for ambiguities and testability. They plan tests and even automate some. By the time the code is written, much testing is done.

Although shift-left isn't a one-size-fits-all approach, there are some key practices to transform your development workflow:

Shift-left testing demands clear communication and collaboration between developers and testers. Regular interaction fosters a common knowledge of project objectives and potential impediments. Working together allows them to understand the code better, identify problems faster, and build better solutions. This collaboration promotes a sense of shared responsibility for quality, resulting in higher-quality software. Adopting a testing tool with a centralized communication capability across stakeholders is a great starting point when implementing a shift-left testing culture in your team. 

Shift-left testing is based on the principles of speed and continuous testing, which are challenging to achieve manually. QA teams should therefore adopt automated testing to enhance the rate of performance. For example, if you were building a SaaS healthcare solution, it would be challenging and time-consuming to cover all the use cases and modules solely via manual testing. You can employ automated regression testing that can incrementally perform sanity and smoke tests during development. Automated performance tests can also simulate high-demand scenarios to assess the application's performance under stress, which gives the dev and QA teams real-time feedback and a better perspective on any major trends popping up during testing. 

Continuous Integration and Continuous Delivery/Deployment (CI/CD) are tools and techniques for automating, accelerating, and streamlining the software development lifecycle (SDLC). When combined with testing, they improve a company's agility, flexibility, and adaptation to business requirements. CI pipelines automatically test and validate new code changes before they are merged into a common repository. CD pipelines go even further, ensuring that the application can be deployed consistently and reliably in the given environment.

CI/CD pipelines are critical for shift-left testing because they enable rapid and continuous code integration and testing. This speeds up feedback loops, allowing defects to be spotted and fixed early in the development process, thereby improving software quality and efficiency. To effectively implement shift-left testing, you need to adopt a test orchestration solution that accelerates test execution speed and supports efficient CI/CD pipelines. 

Shift-left testing requires developers to focus on creating high-quality, secure code from the very start. Don't merely write code to meet deadlines. Understand how your code will be maintained, scaled, and safe in the future. Code reviews are a critical step to sustaining secure and high-quality code. In shift-left testing, you should constantly review your code as you go, rather than at the end. You can use static analysis tools and review code with peers to identify any bugs that you may have overlooked before. The sooner you detect and repair a bug, the less time you'll waste.

Additionally, you must build with the end in mind. Consider the end user and how your code will function in the overall system. Will it be easy to upgrade and secure over time? Implement quality through explicit architecture, modular components, and security best practices. Avoid accumulating technical debt which will slow the team down later.

At its core, shift-left is a cultural shift that emphasizes quality from the get-go and requires buy-in from everyone involved to reap the benefits. Developers need to embrace a broader responsibility for code quality, and testers need to be involved earlier in the development process. By working collaboratively and adopting the right practices, you can leverage the power of shift-left testing to deliver higher-quality software, faster.

The migration to shift-left is challenging, but by focusing on mindsets over tools and taking an iterative approach, it can be achieved. The rewards of faster delivery of higher quality, more secure software make the investment worthwhile. Shift-left is the future of software development, so take steps now to make the cultural transformation in your organization.