Spiral Testing Approach


The purpose of software testing is to identify the differences between existing and expected conditions, i.e., to detect software defects. Testing identifies the requirements that have not been satisfied and the functions that have been impaired. The most commonly recognized test objective is to identify bugs, but this is a limited definition of the aim of testing. Not only must bugs be identified, but they must be put into a framework that enables testers to predict how the software will perform.

In the spiral and rapid application development testing environment there may be no final functional requirements for the system. They are probably informal and evolutionary. Also, the test plan may not be completed until the system is released for production. The relatively long lead time to create test plans based on a good set of requirement specifications may not be available. Testing is an ongoing improvement process that occurs frequently as the system changes. The product evolves over time and is not static.

The testing organization needs to get inside the development effort and work closely with development. Each new version needs to be tested as it becomes available. The approach is to first test the new enhancements or modified software to resolve defects reported in the previous spiral. If time permits, regression testing is then performed to assure that the rest of the system has not regressed.

In the spiral development environment, software testing is again described as a continuous improvement process that must be integrated into a rapid application development methodology. Testing as an integrated function prevents development from proceeding without testing. Deming’s continuous improvement process using the PDCA model will again be applied to the software testing process.
Before the continuous improvement process begins, the testing function needs to perform a series of information-gathering planning steps to understand the development project objectives, current status, project plans, function specification, and risks.

Once this is completed, the formal Plan step of the continuous improvement process commences. A major step is to develop a software test plan. The test plan is the basis for accomplishing testing and should be considered an ongoing document, i.e., as the system changes, so does the plan. The outline of a good test plan includes an introduction, the overall plan, testing requirements, test procedures, and test plan details. These are further broken down into business functions, test scenarios and scripts, function/test matrix, expected results, test case checklists, discrepancy reports, required software, hardware, data, personnel, test schedule, test entry criteria, exit criteria, and summary reports.

The more definitive a test plan is, the easier the plan step will be. If the system changes between development of the test plan and when the tests are to be executed, the test plan should be updated accordingly.

The Do step of the continuous improvement process consists of test case design test development and test execution. This step describes how to design test cases and execute the tests included in the test plan. Design includes the functional tests, GUI tests, and fragment system and acceptance tests. Once an overall test design is completed, test development starts. This includes building test scripts and procedures to provide test case details.

The test team is responsible for executing the tests and must ensure that they are executed according to the test design. The do step also includes test setup, regression testing of old and new tests, and recording any defects discovered.

The Check step of the continuous improvement process includes metric measurements and analysis. “Quality Through a Continuous Improvement Process,” crucial to the Deming method is the need to base decisions as much as possible on accurate and timely data. Metrics are key to verifying if the work effort and test schedule are on schedule, and to identify any new resource requirements.
During the check step it is important to publish intermediate test reports. This includes recording of the test results and relating them to the test plan and test objectives.

The Act step of the continuous improvement process involves preparation for the next spiral iteration. It entails refining the function/GUI tests, test suites, test cases, test scripts, and fragment system and acceptance tests, modifying the defect tracking system and the version and control system, if necessary. It also includes devising measures for appropriate actions relating to work that was not performed according to the plan or results that were not what was anticipated. Examples include a reevaluation of the test team, test procedures, and technology dimensions of testing. All the above is fed back to the test plan, which is updated.

Once several testing spirals have been completed and the application has been verified as functionally stable, full system and acceptance testing starts. These tests are often optional. Respective system and acceptance test plans are developed defining the test objects and the specific tests to be completed.

The final activity in the continuous improvement process is summarizing and reporting the spiral test results. A major test report should be written at the end of all testing. The process used for report writing is the same whether it is an interim or a final report, and, like other tasks in testing, report writing is also subject to quality control. However, the final test report should be much more comprehensive than interim test reports. For each type of test it should describe a record of defects discovered, data reduction techniques, root cause analysis, the development of findings, and follow-on recommendations for the current and/or future projects.

The methodology provides a framework for testing in this environment. The major steps include information gathering, test planning, test design, test development, test execution/evaluation, and preparing for the next spiral. It includes a set of tasks associated with each step or a checklist from which the testing organization can choose based on its needs. The spiral approach flushes out the system functionality. When this has been completed, it also provides for classical system testing, acceptance testing, and summary reports.
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