One 、 The basic elements of test cases

The test case （Test Case） It is a set of sets provided to the tested system for the purpose of implementing the test , This set of collections contains ： Test environment 、 Operation steps 、 Test data 、 Elements such as expected results .
A good test case is that a person who is not familiar with the business can also test quickly according to the use case
Criteria for evaluating test cases ： Compare the evaluation criteria of good and bad code

• Use cases are clearly expressed , No ambiguity .
• The use case has strong operability .
• The input and output of use cases are clear . A use case has only one expected result .
• The maintainability of use cases is good .
• Use cases have high coverage of requirements .
• Exposure procedures Bug Your ability is strong .

Two 、 Design method of test case

2.1 The overall design method of test cases

Demand based design
RBT( Requirements-Based Testing) It is a requirement based testing method , Will make the test more effective , because It enables testing to focus on the root causes of quality problems , Demand .
Requirements based testing is one of the most fundamental software testing , Focus on the following two key issues .
（1） Verify that the requirements are correct 、 complete 、 No ambiguity , And the logic is consistent .
（2） From you to “ Black box ” The angle of , Design sufficient and necessary test sets , To ensure that the design and code can fully meet the requirements .

2.2 Specific design method （ Black box testing ）

2.2.1 Equivalence class

Input... As required （ The output will be considered in special cases ） Divided into several equivalent classes , Select a test case from the equivalence class , If this test case passes the test , It is considered that the test of the equivalent class represented passes , In this way, you can use fewer test cases to achieve as many functional coverage as possible , Solved the problem of not exhaustive testing .

• Effective equivalence class ： The specification of the procedure is reasonable 、 A collection of meaningful input data , Use valid equivalence classes to verify whether the program has achieved the functions and performance specified in the specification
• Invalid equivalence class ： According to the requirement specification , A collection that doesn't satisfy the requirements .

Equivalence classes only consider the classification of input fields , The combination of input fields is not considered , Other design methods and supplements are needed .

2.2.2 The boundary value

Boundary value analysis is a kind of black box test method to test the input or output boundary value . Generally, the boundary value analysis method is used as a supplement to the equivalence class division method , In this case , Its test case comes from the boundary of equivalence class .

2.2.3 Cause and effect diagram

Cause and effect diagram is a simplified logic diagram , It can intuitively show the program input conditions （ reason ） And output actions （ result ） The interrelationship between . Causality diagram method is a systematic method to design test cases with the help of graphics , It is especially suitable for the program under test with a variety of input conditions 、 The output of the program depends on the input conditions .

The steps of designing test cases by causality diagram method are as follows ：
(1) Analyze all possible inputs and possible outputs .
(2) Find out the correspondence between input and output .
(3) Draw a cause and effect diagram .
(4) Turn the cause and effect diagram into a decision table .
(5) Match the decision table to each test case .

2.2.4 Orthogonal arrangement

The purpose of orthogonal method is to reduce the number of use cases . Cover pairs of inputs with as few use cases as possible .
Orthogonal test design (Orthogonal experimentaldesign) It is a design method to study multi factors and multi levels , It is based on orthogonality , Some representative points are selected from the total level combination of test factors for the test , Through the analysis of this part of the test results, we can understand the overall test situation , Find the best combination of levels . Orthogonal experimental design is a method based on orthogonal table 、 high efficiency 、 Fast 、 An economic experiment .

• factors （Factor）： In an experiment , The variables to be investigated are called factors （ Variable ）
• level （ Bit level ）（Level）： Within the scope of the test , The value of the factor being investigated is called the level （ Value of variable ）
  Composition of orthogonal table ：
• Row number (Runs)： The number of rows in an orthogonal table , That is, the number of tests , use N representative .
• Factor number (Factors)： The number of columns in an orthogonal table , use C representative .
• Horizontal number (Levels)： The maximum number of values that can be obtained by any single factor . The values contained in the orthogonal table are from 0 To count “ Horizontal number -1” Or from 1 To “ Horizontal number ”, use T representative .
• The representation of an orthogonal table ： L= Row number ( Horizontal number * Factor number ) L=N(TC)
• Two properties of orthogonal table ：（1） The numbers in each column appear the same number of times .（2） Each ordinal pair of any two columns has the same number of occurrences .

The steps of designing test cases by orthogonal method ：
1、 What are the factors （ Variable ）
2、 What are the levels of each factor （ Value of variable ）
3、 Choose a suitable orthogonal table
4、 Map the values of variables to the table
5、 Consider the combination of factor levels in each row as a test case
6、 Add use case combinations that you think are suspicious and do not appear in the table

2.2.5 Scene design method

Today's software almost uses event triggering to control the process , When the event is triggered, the scene is formed , Different triggering sequence and processing results of the same event form event flow . This method can vividly describe the scene when the event is triggered , It is helpful for the test designer to design test cases , Test cases are easier to understand and execute .
A typical application is to use business flow to connect isolated function points , Build an overall business sense for testers , So as to avoid falling into the wrong tendency of ignoring the key points of business process in functional details .

2.2.6 Wrong guess

Error guessing is a test method that experienced testers like to use .
Based on experience and intuition , Find out what you think may be wrong in the program , Design test cases purposefully . Experience may come from more testing of a business , It can also come from the feedback of after-sales users , Or sort it out from the fault management library bug. Sort out where the product was prone to problems in the past , The more problems there are , Potential bug The more .
Testers can use other methods of designing test cases to design test cases of requirements , Use error guessing as a supplementary way .

2.2 What is the validity of test cases ？

1、 The function corresponding to the test case has been deleted , Inoperable
2、 Executing a test case does not find BUG, Actually there are BUG
3、 Executing a test case found BUG
4、 Executing a test case does not find BUG, Actually BUG The modified