Shift Left vs Shift Right: Why You Need Both For Testing

If you are a software engineer, chances are you have heard “Shift Left” tossed around in stand-ups, sprint reviews, and tech talks more times than you can count. It has become a mantra in modern development, and for good reason. Shift left allows catching bugs early, continuous feedback for developers, and delivering clean, reliable code. But is it enough on its own?

Engineers know firsthand that no amount of pre-deployment testing can fully replicate the complexity and unpredictability of live, production environments. This is where “Shift Right” comes in, allowing for testing and fixing bugs that appear in actual user scenarios.

Below, we will explain the essentials of shifting left and shifting right and show how these two approaches complement each other. 

What is Shifting Left in Testing?

"Shift Left" in software testing refers to the practice of moving testing activities to earlier in the software development lifecycle (SDLC). This enables catching and addressing defects, vulnerabilities, and inefficiencies as soon as possible in the development process, before they become full-blown system failures that are complicated and expensive to fix.

For example, shifting left performance testing enables identifying and addressing performance bottlenecks during development, rather than waiting for a full-fledged system to deploy. Developers can then address the root cause of the bottleneck on time, avoiding (for example) a web application crash when real user traffic spikes.

The term “shift left” arises from the left-to-right timeline representation of the SDLC, starting with design and development and ending in deployment. “Shifting left” means transitioning the testing “to the left” of the development timeline, and conducting testing during development rather than in production.

The shift left method is foundational in modern software engineering approaches such as Agile, DevOps, and CI/CD. This is because shift left supports rapid development cycles with minimal delay, drives higher quality code, and can be continuously automated throughout the SDLC. Shift left testing is opposed to the waterfall approach, aka “shift right”, where testing takes place at the end of the SDLC.

Core Principles of Shift Left Testing

• Test Automation - Automation is key to enabling early testing without becoming a bottleneck. API tests, load tests, functional tests, and other types of tests are automated to ensure constant validation as code evolves. Testing tools are often integrated into CI/CD pipelines, and tests are triggered every time there is a new build, every sprint, or when determined by the engineering team. 
• Continuous Feedback Loop - Automated testing generates actionable feedback immediately. Bugs that are found can be quickly prioritized and fixed. This drives higher quality software for customers and accelerates time-to-market.
• Collaborative Culture - With testing being an integral part of the SDLC, testing is no longer the sole responsibility of a QA team. Rather, developers contribute to writing tests and managing test suites and DevOps run test automation. But shifting left goes beyond mere task allocation. Shifting left embodies a shared responsibility culture where testing supports each engineer’s goals and KPIs and encourages working together to build a better product for end-users.

Benefits of Shift Left Testing

Engineering organizations have been incorporating shift left testing practices for the past decade. This is due to the following professional benefits:

• Improved Software Quality - Continuous testing and immediate feedback cycles ensure that issues are addressed before they snowball into system-wide failures.
• Faster Time-to-Market - Early bug resolution minimizes delays caused by late-phase rework, enabling teams to deliver high-quality software to end-users faster.
• Enhanced Team Morale - Developers appreciate the immediate feedback, reducing frustration over last-minute bug hunts.
• Improved Developer Productivity - Faster feedback loops allow developers to address issues before context-switching diminishes efficiency.
• Lower Cost of Fixes - The cost to fix a defect increases exponentially as it moves downstream. Fixing a bug in production can cost significantly more than catching it during coding.

What is Shift Right in Testing?

“Shift Right” in testing refers to the practice of post-deployment testing in production environments. This concept contrasts with the aforementioned "Shift Left" approach, where testing occurs earlier in the software development life cycle.

While Shift Left prioritizes early defect detection during development and design phases, Shift Right aims to validate the application in real-world scenarios. It ensures software performs reliably under actual production conditions, aligns with user expectations, and adapts to evolving requirements.

Core Principles of Shift Right Testing

• Production Monitoring and Testing - Live testing directly in production, observing application behavior under real traffic and the user experience under real user scenarios.
• Balancing Risk and Reliability - Shift-right testing acknowledges the risks of testing in production while striving for quality assurance. This includes safeguarding critical systems with robust backup and rollback mechanisms (A/B testing or blue-green deployment), conducting tests in controlled production environments (chaos engineering), and gradually deploying and scaling new features to minimize impact (canary testing).
• Continuous Delivery - Integration with DevOps pipelines to ensure swift iteration and deployment cycles. Time is of the essence here since the risk is high.

Benefits of Shift Right Testing

• Higher Confidence in Production Releases - By testing in the actual environment, teams can better understand how the application is performing and ensure it is usable and reliable.
• Improved User-Centric Development - Real-world feedback enables teams to ensure the application addresses actual user needs and behaviors, like user journeys and the user experience.
• Enhanced System Resilience - By proactively addressing live failures, organizations build more robust and fault-tolerant systems.

Shift Left vs Shift Right Testing: Why You Need Both

Both shift left testing and shift right testing sound appealing in their own right. But can organizations simply choose one approach and stick to it? Why should organizations invest resources and efforts in adopting both approaches?

Both Shift Left and Shift Right strategies are required for achieving a robust, holistic approach to software quality. Adopting only one approach creates blind spots that leave the system vulnerable:

Shift Left Alone

• Overemphasis on pre-deployment testing may result in gaps when handling real-world conditions, as certain issues only emerge under production workloads.
• Early testing may miss nuanced user experiences and behavioral trends.

Shift Right Alone

• Sole reliance on production testing risks delivering low-quality software to end users.
• Fixing issues in production can lead to downtime, damaged reputation, high costs, and frustrated users.

A Unified and Complete Testing Strategy: The Left-Right Balance

Forward-thinking organizations should consider implementing testing as a continuum, spanning both ends of the spectrum. This is achieved through continuous testing, a practice that integrates testing across all stages of the software lifecycle, both shift left and shift right.

Benefits of Shifting Left and Shifting Right Together

Engineering organizations that implement both shift left and shift right testing will enjoy:

• 360° Quality Assurance - Testing throughout development, build, release, and production ensures more bugs and issues are caught and reduces the chances of issues affecting end users. This improves software quality and users satisfaction, end-to-end.
• Accelerated Delivery - Continuous feedback accelerates time-to-market before production and enables addressing issues affecting customers in production environments. This reduces bottlenecks in both development and operations.
• Higher Confidence - With shift left teams release updates more frequently and with fewer risks, ensuring both speed and stability. But with shift right they also know that issues in production will be caught and addressed, reducing stress levels and garnering certainty that the highest quality product will be delivered to customers. 

How to Implement Shift Left and Shift Right Testing Together

Ready to kickstart your continuous testing strategy? Here are three practices to get you started:

1. Testing Tools That Support Shift Left and Shift Right - Choose a vendor that enables you to shift left and shift right. This means flexibility and ease when scripting and running tests, support for multiple kinds of tests, integrations into CI/CD pipelines, integrations with APMs, automations, and the ability to collaborate as a team on the tool.
2. Cultural Emphasis - Foster a quality-first culture, where every member (developer, tester, operations) shares accountability and feels responsible for code quality at every phase.
3. Feedback Loops - Incorporate feedback loops at all stages. Create automated workflows that provide developers with reports on code coverage, test results, errors,  incident data, and user experience insights. Integrate these into project management tools (e.g., JIRA) to prioritize fixes.

Bottom Line

Whether you have relied on only shift left testing or only shift right testing, hopefully it is clear now why the two complement each other and employing both in testing strategy will unlock superior software quality.

With BlazeMeter, you get the best of both worlds: shift left testing and shift right testing to create a comprehensive, continuous testing solution. You can get started with BlazeMeter's unrivaled continuous testing platform for FREE today!

Start Testing Now