V model
The V model is an improvement of the well-known waterfall model. It was first proposed by Paul Rook in 1980 and appeared in the publication of the British National Computing Center in 1990 to improve the efficiency and effectiveness of software development. The waterfall model divides the software life cycle into six stages: planning, analysis, design, coding, testing, and maintenance. Since early errors may not be discovered until the later testing stage of development, they may bring serious consequences.
The V model improves the waterfall model at this point. During the life of software development, development activities and testing activities begin almost at the same time. These two parallel dynamic processes will greatly reduce the chance of bugs and errors.
From left to right, the process in the V model describes the basic development process and testing behavior. The phases are roughly divided into requirements analysis, outline design, detailed design, coding, unit testing, integration testing, system testing, and acceptance testing. It clearly indicates the different levels that exist in the testing process, and clearly describes the correspondence between these testing phases and the various phases during the development process.
The system test corresponds to the requirement analysis link, that is to say, the test cases of the system test are designed according to the requirement specification. The developer designs the software according to the requirement specification, and the tester designs the system test case according to the requirement specification. . After the outline design, the developers design the software in detail according to the outline design, and the testers design integration test cases according to the outline design. After the detailed design, the developers code according to the detailed design, and the testers design unit test cases according to the detailed design. After the coding is completed, the tester tests the set test unit according to the unit test case. After the unit test is completed, the integration test is performed, then the system test is performed, and finally the acceptance test is performed.
Limitations: Treat the testing process as a stage after requirements analysis, system design, and coding. Ignoring the requirements analysis and verification of the system design by the test, it was not discovered until the later acceptance test.
The solution is that testing will have test case tracking while the software is doing demand analysis, so that program errors and demand deviations can be found as soon as possible, so as to improve program quality more efficiently, reduce costs as much as possible, and satisfy users at the same time. The actual software requirements.
Applicable project scope:
Generally suitable for the development of some traditional information system applications, and some high-performance and high-risk systems, Internet software, or when a system is difficult to be specifically modularized, it is more difficult to make the various components required by the V mode, and more Emphasize iterative development model or agile development model.
W model
The W model was proposed by Evolutif and is a development of the V model.
The W model is composed of two V-shaped models, which represent the testing and development process respectively. The figure clearly shows the parallel relationship between testing and development. Compared with the V model, the W model is more scientific. It is emphasized that testing accompanies the entire software development cycle, and the object of testing is not only the program, but also the requirements, functions, and designs. Testing and development are carried out simultaneously, which helps to find problems as early as possible.
limitation:
Both the W model and the V model regard software development as a series of serial activities such as requirements, design, and coding, and cannot support iteration, spontaneity, and change adjustments.
X model
The basic idea of the X model was proposed by Marick. Mr. Robin F. Goldsmith defined his idea as the X model in his own article. The goal of the X model is to make up for some of the defects of the V model.
Marick's main criticism of the V model is that the V model cannot guide the entire process of the project. He believes that a model must be able to handle all aspects of development, including handover, frequent and repeated integration, and the lack of requirements documentation.
The left side of the X model describes the separate coding and testing for individual program fragments. After that, frequent handovers will be carried out, and finally executable programs will be integrated through integration, and then these executable programs will be tested. The finished product that has passed the integration test can be packaged and submitted to the user, or it can be used as a part of a larger scale and scope of integration. Multiple parallel curves indicate that changes can occur in various parts.
It can be seen from the figure (bottom right) that the X model also locates exploratory testing, which is a special type of test that is not planned in advance. This method can often help experienced testers find more than the test plan. Software error.
Limitations: It may cause a waste of manpower, material resources and financial resources for the test, and the proficiency of the tester is relatively high.
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