The shift-left testing approach helps meet the demands of faster iteration cycles with smaller testing windows. Teams need to adopt proper tools and processes to reap the benefits.
Testing code prior to deployment is a crucial aspect of the software development lifecycle. As development speeds increase, so does the importance of efficient testing that yields productive results.
Up to 85 percent of defects are introduced during the coding phase of development, as articulated by Capers Jones in his book on applied software management. When developers perform more testing earlier in the process, they can improve code quality and lessen the time to fix flaws later in deployed code. Cost also plays a role: a defect in production can cost exponentially more to find and fix than if developers identify and correct the defect in development.
With the right tools and testing approaches, dev teams can use shift-left testing to streamline the development process, improve code quality and cut costs. When teams target low-level functionality, utilize specific testing methods and emphasize standards and communication, shift-left testing can be a valuable addition to the development cycle.
How shift-left testing and tools improve results
Software products are composed of a myriad of small parts: modules, routines, algorithms and interfaces. Developers build each part separately, sometimes in different teams; integrate these parts; and subject them to extensive testing.
The shift-left testing approach focuses testing on the project parts the team completes early in the process, such as modules and other sub-components of the software. Shift-left testing is most effective when looking for granular, low-level code structure and functional/unit trouble.
When developers catch and squash low-level bugs, the project can enter its mid- to later stages of testing -- such as integration and user-acceptance testing -- with greater confidence and faster results.
The most appropriate tools for shift-left testing emphasize more granular, low-level functionality. Other tools for integration, user acceptance testing and performance benchmarking are useful in their roles and belong in the testing toolset alongside the lower-level testers.
Types of shift-left testing
Implementing the shift-left testing approach is more a matter of workflow and timing than a large shift in technology or tools. Many popular testing concepts suit early, frequent and low-level functional testing. Test types associated with shift-left testing include the following:
Static testing. Static testing checks a codebase before it's built. One or more code checkers, also called linters, analyze different aspects of the code for problems such as vulnerabilities, incorrect parameter types and incorrect interface use. Even IDEs provide real-time feedback about code structure, content and common coding punctuation/spelling errors. There are dozens of static code checkers available, such as ESLint and Apache Yetus, and most programming languages have at least one static code checker.
Unit testing. Unit tests offer functional testing for small pieces of code, such as modules or routines. Developers test the pieces of code before those pieces become part of the application. As such, unit testing tools are a good fit for shift-left testing approaches.
Test-driven development (TDD). With TDD, developers write tests before they develop the code. Developers then run the completed code against the tests to validate the code.
Behavior-driven development (BDD). An extension of TDD, BDD establishes a common design language to foster collaboration and understanding among developers and other software project stakeholders. When everyone uses the same terms and concepts, communication is better. Fewer misunderstandings should lead to fewer code defects.
Tools rarely work alone in a shift-left approach. Development teams that successfully shift left implement well-considered and proven coding standards. Coding standards include the organization's common requirements and rubrics for writing code and modules, naming conventions for variables, or subroutines and other guidance. When all developers write code the same way, they can reduce inconsistencies that cause mistakes and defects.
Shift-left testing tools
Since shift-left is a concept rather than a specific technology, organizations can choose from countless testing tools in accordance with their shift-left testing goals. Certain existing tools in their toolkit may already support shift-left testing initiatives. Many tools cater to the shift-left movement:
- Katalon Studio. A low-code test automation tool for continuous testing.
- Ranorex Studio. A codeless test automation tool with multi-language support for shift-left testing.
- Sauce Labs. A pass-or-fail testing tool for every framework, browser, OS, mobile device and API.
- TestLeft. A tool by SmartBear that targets shift-left automated testing with any IDE.
- Testsigma. A cloud-based test automation tool for web, Android and iOS apps and APIs.
Shift-left approaches must fit within DevOps or other CI/CD paradigms. Tool selection should, therefore, include a close assessment of automation and workflow support as well as integration with other CI/CD pipeline tools.
The benefits of shift-left testing
An effectively implemented shift-left initiative can have several effects on the developer environment, including faster testing, quality code and developer engagement.
Faster overall testing. Even CI/CD pipelines can experience delays during the test phase of an iteration cycle. Developers build code, tests run on the code, and then the team gathers results and makes changes as needed. Completing more tests earlier in the process distributes testing between developers and the dedicated testers as well as catches bugs before the team runs extensive/complete test suites.
Better code quality. By moving more of the testing to earlier parts of the cycle, developers have fewer errors and can be more confident in the delivered code. In addition, because more developers are writing tests, shift-left creates plentiful and diverse tests to validate the codebase.
More developer involvement. Testing is a developer activity, but it's often performed by select staff. Shift-left places more of the testing responsibility on coders, which can create better coders with more sensitivity to testing activities and coding standards.
Shift-left testing demands attention to test development and maintenance. With developers writing tests, management of test logic and test data is critical. Teams should add test review and maintenance tasks to the existing development cycle to ensure that they don't overlook changes in test requirements.