Agile Methodology

Most software development life cycle methodologies are either iterative or follow a sequential model (as the waterfall model does). As software development becomes more complex, these models cannot efficiently adapt to the continuous and numerous changes that occur. Agile methodology was developed to respond to changes quickly and smoothly. Although the iterative methodologies tend to remove the disadvantage of sequential models, they still are based on the traditional waterfall approach. Agile methodology is a collection of values, principles, and practices that incorporates iterative development, test, and feedback into a new style of development. For an overview of agile methodology, see the Agile Modeling site at http://www.agilemodeling.com/.
The key differences between agile and traditional methodologies are as follows:

• Development is incremental rather than sequential. Software is developed in incremental, rapid cycles. This results in small, incremental releases, with each release building on previous functionality. Each release is thoroughly tested, which ensures that all issues are addressed in the next iteration.
• People and interactions are emphasized, rather than processes and tools. Customers, developers, and testers constantly interact with each other. This interaction ensures that the tester is aware of the requirements for the features being developed during a particular iteration and can easily identify any discrepancy between the system and the requirements.
• Working software is the priority rather than detailed documentation. Agile methodologies rely on face-to-face communication and collaboration, with people working in pairs. Because of the extensive communication with customers and among team members, the project does not need a comprehensive requirements document.
• Customer collaboration is used, rather than contract negotiation. All agile projects include customers as a part of the team. When developers have questions about a requirement, they immediately get clarification from customers.
• Responding to change is emphasized, rather than extensive planning. Extreme Programming does not preclude planning your project. However, it suggests changing the plan to accommodate any changes in assumptions for the plan, rather than stubbornly trying to follow the original plan.

Agile methodology has various derivate approaches, such as Extreme Programming, Dynamic Systems Development Method (DSDM), and SCRUM. Extreme Programming is one of the most widely used approaches.

Agile Testing: Example

Agile methodology with Extreme Programming and test-driven development was used to develop the Smart Client Offline Application Block. The following are highlights of the approach taken on the project:

• The test team and the development team were not formally separated. The developers worked in pairs, with one person developing the test cases and the other writing the functionality for the module.
• There was much more interaction among team members than there is when following a traditional development model. In addition to using the informal chat-and-develop mode, the team held a 30 minute daily standup meeting, which gave team members a forum for asking questions and resolving problems, and weekly iterative review meetings to track the progress for each iterative cycle.
• Project development began without any formal design document. The specifications were in the form of user stories that were agreed upon by the team members. In the weekly iterative review meetings, team members planned how to complete these stories and how many iterations to assign for each story.
• Each story was broken down into several tasks. All of the stories and corresponding tasks were written down on small cards that served as the only source of design documentation for the application block.
• While developing each task or story, NUnit test suites were written to drive the development of features.
• No formal test plans were developed. The testing was primarily based on the tasks or stories for feature development. The development team got immediate feedback from the test team. Having the test team create the quick start samples gave the development team a perspective on the real-life usage of the application block.
• After the task or story passed all of the NUnit test cases and was complete, quick start samples were developed to showcase the functionality. The quick start samples demonstrated the usage of the application block and were useful for further testing the code in the traditional way (functional and integration tests). Any discrepancies found in this stage were reported immediately and were fixed on a case-by-case basis. The modified code was tested again with the automated test suites and then was handed over to be tested again with the quick start samples.