Orthogonal test method and function diagram method for test case design

Concept of orthogonal test method

basis Galois theory , From a lot of （ experiment ） data （ Test case ） Choose the right amount of , Representative points （ example ）, So as to arrange the experiment reasonably （ test ） A scientific experiment design method . Similar methods include : Cluster analysis method , Factor method, etc .

Orthogonal test method

When using cause and effect diagrams to design test cases , The causal relationship between the cause as an input condition and the output result , Sometimes it's hard to get from the software requirements specification . Often the causality is very large , So that the number of test cases obtained from the cause and effect diagram is amazing , It brings a heavy burden to software testing , In order to effectively , Reasonably reduce the test time and cost , The orthogonal experiment design method can be used to design test cases .

The steps of designing test cases by orthogonal experiment ：

1. Extract function description , Structural factors -- State table

The conditions affecting the experimental indexes are called factors . The condition that affects the experimental factor is called the state of the factor . When using orthogonal experimental design method to design test cases , First, find out the operation objects and external factors that affect the function realization according to the specification of the tested software , Think of them as factors , The value of each factor is regarded as the State . Divide the functional requirements in the software requirements specification , Decompose and expand the overall outline functional requirements layer by layer , Decompose into specific basic functional requirements with relative independence .

In this way, all factors in the software under test can be determined , Provide a reference for determining the weight of . Determining factors and states is the key to designing test cases . Therefore, it is required to determine the value as comprehensively and correctly as possible , To ensure that the design of test cases is complete and effective .

2. Weighted screening , Generating factor analysis table

The selection of factors and states can be weighted according to their importance . According to the action of each factor and state , The frequency of occurrence and the need for testing , Determine the size of the weight .

3. Using orthogonal table to construct test data set

The derivation basis of orthogonal table Galois theory （ It is omitted here , If necessary, you can check the textbooks on Mathematical Statistics ）.

Using orthogonal experimental design method to design test cases , It's better than using equivalence classes , Boundary value analysis , Methods such as cause and effect diagrams have the following advantages : Save testing time ; The number of test cases generated can be controlled ; Test cases have a certain coverage .

Concept of function diagram method

Function diagram consists of state transition diagram and Boolean function . The state transition diagram is described by state and transition . A status indicates where the data is entered （ Or time ）, Migration indicates a change in state . At the same time, it depends on the logical functions represented by the decision table or cause and effect diagram . example , A simplified automatic teller ATM Function diagram of .

Application of function diagram

1. Function diagram introduction

The functional description of a program usually consists of dynamic description and static description . Dynamic description describes the order of input data or the order of transfer .

Static description describes the corresponding relationship between input conditions and output conditions . For more complex programs , Because there are a lot of combinations , therefore , Specifications composed of static specifications are often not enough for testing . The function description must be supplemented by a dynamic description . The function diagram method is to use the function diagram FD Formally represent the functional description of the program , And generate test cases of function diagram mechanically .

The function diagram model consists of state transition diagram and logical function model . The state transition diagram is used to represent the input data sequence and the corresponding output data . In the state transition diagram , Output data and subsequent status are determined by input data and current status . The logical function model is used to represent the corresponding relationship between input conditions and output conditions in the state .

The logical functional model is only suitable for describing static descriptions , The output data is determined only by the input data . A test case consists of a series of states that pass through the test and must rely on input in each state / The output data consists of a pair of conditions . Function diagram method is actually a black box and white box mixed use case design method .

（ In the function diagram method , The concepts and methods of logical coverage and path testing are used , It belongs to the white box test method The content of . Logic coverage is a test case design method based on the internal logic structure of the program . This method requires testers to have a clear understanding of the logical structure of the program . Because the objectives of coverage testing are different , Logical coverage can be divided into : Statement override , Determine coverage , determine - Conditional coverage , Conditional combination covering and path covering . The logical coverage and paths we refer to below are at the functional or system level , To distinguish it from the internal of the program in the white box test .）

2. Test case generation method

Generate test cases from Functional Diagrams , The number of test cases obtained is acceptable . The key problem is how to select test cases from the state transition diagram . If node is used instead of state , Replace migration with an arc , Then the state transition diagram can be transformed into the control flow diagram of a program . The problem is transformed into the path test problem of the program （ Such as white box test ） Problem. .

3. Test case generation rules

In order to move the State （ Test path ） Test cases and logical models （ Partial test cases ） Test cases are combined , Generate practical test cases from function diagrams , The following rules must be defined . Migrate in a structured state （SST） in , Define three forms of loops : The order , Selection and repetition . But it is difficult to distinguish all cycles in a state transition .（ It indicates that the graphics are omitted ）.

4. The process of generating test cases from functional diagrams

a. Generate local test cases : In each state , Generate local test cases from cause and effect diagrams . Local test cases consist of cause values （ input data ） Combine with the corresponding result value （ Output data or status ） constitute .

b. Test path generation : Use the rules above （ Three ） Generate test path from initial state to final state .

c. Test case synthesis : Composite test paths and local test cases in each state in the functional diagram . The result is a sequence of states from the initial state to the final state , And a combination of input data and corresponding output data in each state .

5. Test case synthesis algorithm : Construct a tree with conditions .

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