Shift-left testing

Shift-left testing refers to testing software early in the development process, while shift-right testing refers to testing towards the end of the development cycle. The term, "shift-left" is used to describe the idea of moving software testing earlier in the process, which can help catch defects earlier and reduce the cost of fixing them later. In contrast, "shift-right" refers to testing later in the process, which can help ensure that the software meets the intended requirements and functions correctly before it is released. SHift -left is also the first half of the maxim "test early and often",[1] coined by Larry Smith in 2001.[2][3]

Why Shift Left Testing ?

Shift-left testing is used to catch defects earlier in the software development process before they become more costly and time-consuming to fix. This approach helps improve the overall quality of the software, reduces development costs, and shortens the time to market.

One of the main reasons for shift-left testing is to address defects as early as possible in the development process. According to a study by the IBM Systems Science Institute,[4] the cost of fixing defects increases dramatically as they move further along in the development lifecycle. In fact, the cost of fixing defects during production can be up to 100 times more expensive than if the defect had been caught during the requirements phase.

Another reason for shift left testing is to increase collaboration and communication between different teams involved in software development. By catching defects early, development teams can work more closely with other stakeholders, such as testers and business analysts, to identify and resolve issues before they become more difficult to fix.

There are several tools available to support shift-left testing, including those that use artificial intelligence (AI) and machine learning (ML). AI and ML tools can be used to automate testing activities and optimize test coverage. By using these tools, software developers can identify defects earlier in the development cycle and improve the overall quality of their software products.[5]

Risks of testing later

Shift-left testing aims to prevent the following types of harm because of late testing:

  • Insufficient resources allocated to testing.
  • Undiscovered defects in requirements, architecture, and design, along with significant effort wasted while implementing them.
  • Difficulty debugging (including identifying, localizing, fixing, and regression testing defects) as more software is produced and integrated.
  • A “bow wave” of technical debt that can cause a project to fail.

Examples of shift-left testing

Shift-left testing is an approach that involves moving testing activities to earlier stages of the software development lifecycle (SDLC) to catch defects early, improve software quality, and reduce costs. There are four basic ways to shift testing earlier in the life-cycle, leftward on the classic V-model, which include traditional shift-left testing,[6] incremental shift-left testing, Agile/DevOps shift-left testing, and model-based shift-left testing[8]. Traditional shift-left testing involves integrating testing activities into every phase of the process, while incremental shift-left testing gradually moves testing activities to earlier stages of the SDLC. Agile/DevOps shift-left testing involves continuous testing throughout the development process, using automated testing tools and practices like continuous integration and continuous testing (CI/CT). Model-based shift-left testing uses models to simulate software behavior and identify defects early in the development process.

Traditional shift-left testing

Traditional shift left testing involves moving testing activities to earlier stages of the software development process. This approach aims to catch defects as early as possible, ideally during the requirements and design phases, to prevent them from becoming bigger issues later on. The goal of traditional shift left testing is to improve software quality and reduce costs by catching and resolving issues earlier in the development process.

In traditional shift-left testing, testing activities are typically carried out by dedicated testers who work alongside developers to ensure that testing is integrated into every phase of the SDLC. Testers may be involved in activities such as reviewing requirements, writing test cases, performing code reviews, and executing automated tests.

One benefit of traditional shift-left testing is that it allows issues to be caught and resolved earlier in the SDLC, which can reduce the cost and time required to fix defects later on. Additionally, by involving testers earlier in the development process, communication and collaboration between testers and developers can be improved, leading to better software quality overall.

Incremental shift-left testing

Incremental shift-left testing is a software testing approach that gradually moves testing activities to earlier stages of the software development process in a phased manner. This approach enables organizations to implement shift-left testing at a comfortable pace, starting with small changes and gradually increasing the level of testing activity in earlier stages of the development process.

In incremental shift-left testing, testing activities are moved incrementally to earlier stages of the development process, starting with the coding phase and moving backward to earlier stages such as requirements gathering and design. By doing this, issues can be identified and resolved earlier in the development process, leading to improved software quality and reduced costs.

For instance, organizations can start with unit testing and static code analysis during the coding phase, then gradually add more testing activities such as requirements testing and design review in earlier stages of the development process. Unit testing involves testing individual units or components of code to ensure they work correctly, while static code analysis helps to identify potential errors or bugs in the code before it is deployed.

Agile/DevOps shift-left testing

Agile/DevOps shift-left testing is a way of testing software that is often used in Agile and DevOps software development methods. Instead of waiting until the end of the development process to perform testing, testing activities are integrated into the entire software development process.

In Agile/DevOps shift-left testing, testing is performed continuously during the development process. Testers work closely with developers and other team members to catch and resolve defects as early as possible. This method emphasizes communication and collaboration between team members to make sure that testing is integrated into every part of the software development process.

One way of implementing Agile/DevOps shift-left testing is to use automated testing tools and practices like continuous integration and continuous testing. These methods allow organizations to catch defects early and prevent them from causing bigger problems later on.


Model-based shift-left testing

Model-based shift-left testing is a software testing approach that uses models to simulate how the software works. Testers use these models to detect defects early in the development process and make changes to the software design before the actual development begins. This approach can help ensure that the software meets the intended requirements and functions correctly before it is built.

To use model-based shift-left testing, testers create a graphical model that represents the software behavior and use automated tools to test the model. This allows testers to test different scenarios and validate the software design before the actual coding process starts. By identifying defects early in the development process, developers can avoid costly rework later on.

According to an article in "Software Testing Help", model-based shift-left testing "can help to reduce the cost of software development by minimizing the need for rework and improving software quality through early detection and correction of defects."

References

  1. Microsoft (2012). "Test Early and Often". Retrieved 27 March 2015.
  2. Smith, Larry (September 2001). "Shift-Left Testing". Dr. Dobb's Journal. 26 (9): 56, 62.
  3. "Sep01: Shift-Left Testing". 2014-08-10. Archived from the original on 2014-08-10. Retrieved 2019-09-06.
  4. IBM Systems Science Institute (2004). The impact of defects on productivity. IBM.
  5. J. Gao, C. Tao, D. Jie, S. Lu (2019). What is AI Software Testing? and Why. IEEE.{{cite book}}: CS1 maint: multiple names: authors list (link)
  6. Lisa Crispin & Janet Gregory (2014). Agile Testing: A Practical Guide for Testers and Agile Teams. Velocity Partners.
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