Delivering high-quality, timely software is crucial for any organization that creates digital products and services. However, this can often be challenging with traditional testing approaches that only start after development is completed. Shift left testing is emerging as a new norm to enable more effective testing by starting testing activities earlier in the development lifecycle.
In this comprehensive guide, we will explore what shift left testing is, its benefits over traditional testing, the different types of shift left testing, challenges to be aware of, and best practices for implementation. By the end, you will have a clear understanding of how to leverage shift left testing as a new norm to boost software quality in 2024 and beyond.
What is Shift Left Testing?
Shift left testing is the practice of moving testing activities to earlier stages of the software development lifecycle. Rather than waiting until after code is written to begin testing, testing starts while requirements are being gathered, during design, and through development.
Figure 1: Traditional vs. Shift Left Testing Models (Source: Research.Aimultiple.com)
This shift left in testing aims to detect defects and mitigate risks earlier. Bugs that may have been caught late in development or after launch can now be identified and fixed when they are simpler and less expensive to resolve.
Overall, shift left testing focuses on:
-
Continuous testing – Testing is not a one-time phase but rather ongoing throughout the development process. With continuous testing, tests are executed repeatedly as code changes to catch regressions.
-
Early engagement – Testing team skills are leveraged during requirements, design, and development phases rather than just validating completed code. This enables collaboration on quality earlier.
-
Risk-based – Higher risk aspects, such as security or complex functions, are tested earlier rather than waiting for end-to-end testing.
-
Automated – Automated tests are built early and run often to enable continuous testing. Unit, integration, and regression tests are automated.
-
Collaborative – Cross-functional teams with shared goals and quality culture collaborate closely on requirements, design and testing. Issues are resolved faster.
This methodology represents a cultural shift towards quality and prevents defects rather than simply finding them late. The end goal is to deliver better software faster and more efficiently.
The Growing Costs of Defects
To understand why shifting left is imperative, it is instructive to consider research on the costs of defects over the development lifecycle. Studies have shown that the later a defect is detected, the more expensive it becomes to fix.
For example, IBM found that defects detected post-deployment can be 100 times more expensive to fix than if caught during requirements and design phases, as shown in Figure 2.
Figure 2: IBM Data on Cost of Fixing Defects Increases Over Time (Source: ResearchGate)
Similarly, a study by CAST Software found the cost to fix bugs found during production was over 15 times more than during the design phase, as shown in Figure 3.
Figure 3: CAST Software Data on Cost of Fixing Defects Over Development Lifecycle (Source: Dzone)
The data clearly shows the significant costs organizations incur by delays in defect detection. Shifting testing left enables earlier detection and considerable cost savings.
4 Types of Shift Left Testing
There are several ways shift left testing can be applied based on the development methodology being used. Here we explore the 4 main types of shift left testing.
1. Traditional Shift Left Testing
This approach aligns with the traditional V-Model of development. Testing activities are shifted earlier within each phase of development as shown below.
Figure 4: Traditional Shift Left Testing V Model (Source: Wikipedia)
Testing is integrated into requirements analysis, system design, software design and coding, and system integration. For example, API testing and unit tests would be added during coding rather than after.
This model is straightforward to implement but may not take full advantage of continuous testing across the lifecycle.
2. Incremental Shift Left Testing
With large and complex projects, using an incremental model can make shift left testing more manageable. In this approach, the project is broken down into smaller increments that build on each other.
Figure 5: Incremental Shift Left Testing Model (Source: Wikipedia)
Testing is shifted earlier and becomes continuous within each increment. Requirements, design, build, and test steps are repeated for each increment. This allows for incremental deliveries and feedback.
3. Agile/DevOps Shift Left Testing
For teams using Agile, Scrum, or DevOps practices, shift left testing aligns with iterative delivery. Testing is integrated into development sprints and build/test automation pipelines.
Figure 6: Agile DevOps Shift Left Testing Model (Source: Wikipedia)
Rather than waiting for full build/test cycles, testing happens continuously as part of development. Automated unit, integration, and regression tests are emphasized to enable continuous testing.
4. Model-Based Shift Left Testing
In this approach, testing is shifted all the way to the left of the lifecycle during requirements gathering and architectural modeling.
Figure 7: Model Based Shift Left Testing (Source: Wikipedia)
Testing activities focus on models and simulations of the requirements, architecture, and design. Defects in requirements and design can be detected before full implementation begins. This provides the earliest feedback but requires modeling expertise.
Benefits of Shift Left Testing
Adopting a shift left testing strategy provides many benefits compared to traditional testing approaches:
Finds Defects Earlier
Bugs are detected earlier in the lifecycle rather than late in development or post-launch. This makes them cheaper and faster to fix.
Reduces Costs
Studies show the cost to fix defects grows exponentially later in development. Shift left testing greatly reduces costs by preventing accumulation of defects. Each bug found earlier saves significant time and money.
Improves Quality
Continuously testing and fixing defects produces higher quality code and user experiences. Issues are fixed incrementally rather than accumulating.
Enables Faster Delivery
Early testing facilitates rapid feedback to developers that leads to faster defect resolution. Incremental builds stay on schedule.
Increases Customer Satisfaction
Higher quality software delivered faster and without cost overruns satisfies customers. Quality drives loyalty.
Supports Innovation
By preventing defects upfront, teams can focus on creating business value rather than fire-fighting bugs.
Facilitates Collaboration
Cross-functional teams work together towards shared quality goals. Knowledge is shared across roles leading to collective ownership.
Challenges with Shift Left Testing
While the benefits are compelling, adopting shift left testing also poses some challenges that must be addressed:
Requires Mindset Shift
It represents a significant change for developers and testers accustomed to more traditional workflows. Without proper change management, teams may resist altering existing practices.
Increased Collaboration Needed
Developers may see testing as not their responsibility. Siloes must be broken down through more integrated teamwork and collective code ownership.
Demands New Skills
Testers need skills to engage earlier and developers must own quality. Training on new tools, automation, and processes may be required.
Not All Testing Can Be Shifted
Certain types of testing still need to happen later in development or post-release, such as exploratory and usability testing. Balance is required.
Can Increase Test Maintenance
More automated tests to maintain through code changes may burden teams without the right regression test processes. Balance automation with manual testing.
Potential for Waste
If foundational code is not ready, some early test creation efforts could be wasted rework. Ensure readiness before testing dependencies.
Metrics and Reporting Changes
Traditional defect and test coverage metrics may not work the same. KPIs need to be adapted based on new processes.
With the proper change management, communication, and phased introduction, these challenges can be effectively mitigated. The key is taking steps tailored to your organization‘s culture and project characteristics.
Best Practices for Shift Left Testing Success
Based on industry experience, here are 5 best practices I recommend to enable effective shift left testing:
1. Phase in Change Gradually
Trying to overhaul all testing processes at once is unlikely to succeed. Introduce changes incrementally over time. Pilot shift left on lower risk projects first.
2. Involve the Team
Collaborate with testers, developers and other roles to get buy-in. Make it clear how they benefit rather than a top-down mandate. Address concerns transparently.
3. Start with Unit Testing
Work with developers to build out automated unit tests early in development. Fixing code issues here prevents cascading defects down the line.
4. Automate Regression Testing
Automate repetitive system and integration testing to enable continuous regression as code changes. Automation is key for speed.
5. Continuously Inspect and Adapt
Analyze results of shifts quantitatively. Keep adapting the processes based on lessons learned. Create a feedback loop for continuous improvement.
6. Foster Collaboration
Break down siloes between roles through collaborative rituals like specification workshops, design reviews, and daily stand ups.
7. Provide Hands-On Training
Don‘t just tell teams to shift left. Provide hands-on training for new skills like test automation, infrastructure coding, and exploratory testing.
8. Design Reusable Tests
Create modular, data-driven tests that can evolve as code changes without maintenance overhead. Leverage test libraries.
9. Integrate Testing Tools
Use tools that integrate across the lifecycle and provide traceability as code moves left. Leverage test management capabilities.
10. Update Metrics and Reporting
Go beyond traditional coverage and defect metrics. Track new KPIs for continuous testing, collaboration, quality trends, and prevention.
Conclusion and Future Outlook
Shift left testing is fast becoming crucial for digital transformation success by delivering higher quality applications faster. As technology trends like cloud, DevOps, AI, and customer experience evolve, shift left enables software teams to adapt through early and continuous testing.
This new culture and mindset will require organizations to rethink roles, invest in collaboration and skills, and embrace test automation. The effort pays major dividends in preventing defects and the exponential costs associated with finding them late. Companies that master shift left testing will gain real competitive advantage.
2022 has seen shift left adoption expand, but 2023 will likely see it become the new norm. As shift left testing proves its value, digital leaders across sectors will need to make this a priority to keep up. Built-in quality through shift left testing represents the next frontier for software excellence.
Based on my experience helping organizations implement shift left, I expect this trend to accelerate in 2024. As more turn the corner on digital transformation, uptake of agile, DevOps and advanced QA will continue rising. This will make shift left pivotal for success. I foresee shift left becoming integral to enterprise software development within the next 2 years.
