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Thursday, December 12, 2013

Some white box testing techniques – part 1

In this article we shall give a brief description of the various techniques that are used in white box testing.

- Control flow testing: This is more of being similar to structural testing and is based on the control flow model of the application that is being testing. In control flow testing certain paths among all are selected judiciously so as to provide maximum coverage. The paths are chosen so that a decided thoroughness in the testing process is maintained. This means that paths that have been selected should be enough so as to cover all the statements at least once. It is usually applied to the new software systems that have to be put under unit testing (unit level white box testing). This technique assumes that there are correct specifications, correctly assessed and defined data, no bugs in the program except those in the control flow. The number of control flow bugs is fewer in the programs that are written using object – oriented or structured programming languages. This technique makes use of a flow graph usually called the control flow graph that represents the control structure of the program.

- Data flow testing: Flowing data in a program is what keeps a program active. If there is no data flow, the program won’t be able to perform any operation. The program’s data flow needs to be tested to ensure that it is constant and efficient. Data flow testing also requires a data flow graph. This graph is required to know where and why the data is going or if it is going to correct destination or not. This testing helps in uncovering any anomalies that might restrict the flow of data in a program. Knowing these anomalies also helps in branch and path testing. A number of methods and techniques go in to data flow testing for exploring various events that are taking place in the program, whether right or wrong. It is used for checking whether all the data objects have been initialized or not and makes sure that they are used at least once in the whole program. Arrays and pointers are considered to be the two major elements that play a critical role in data flow testing. These two elements cannot be neglected. Data flow testing might include static anomaly detection, dynamic anomaly detection and anomaly detection through compliers.

- Branch testing: As the name suggests, this testing technique is used for testing all the branches of all the loops within a program. Here branch coverage plays a great role. It has to be made sure that each and every branch in the program is executed once. Thus the test cases are designed in such a way that all the branches are covered. This technique is just for complementing the white box testing at unit testing level. The programmers aim that their test cases must provide 100 percent branch coverage. Also the coverage has to be proper otherwise it can lead to other potential problems such as removal of the code that was actually correct and insertion of faulty code. But providing 100 percent coverage is not possible and we are always left with some bugs and errors that never come to the scene. Branch testing lets you uncover errors which lie in those parts of the program that are least executed or never executed. But there is a potential drawback too; which is; that it is very ineffective in uncovering errors in interactions of structures and decisions. Because of this drawback, the testers usually prefer to go for path testing.

Read more about this in Part 2 - White Box testing techniques.

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