Method of test case design -- move combination, causal judgment

introduction

The first part talks about the equivalence class division and boundary value analysis , These two methods only consider a single input condition , Various combinations of input conditions are not considered 、 The scenario of mutual restriction between input conditions . Based on this short board , Cause and effect diagram method and decision table method came into being .

Cause and effect diagram

Concepts and principles

Definition

A graphical tool that describes the combination of input conditions and the corresponding output of each combination , It is suitable for checking various combinations of program input conditions .

Principle of method

When drawing the cause and effect diagram , The reason is on the left , The result is on the right , Arranged from top to bottom , And according to the relationship between causes and results specified in the functional specification , Connect with the following basic symbols , Some intermediate nodes can also be introduced into the cause and effect diagram .
The basic graphic symbol of cause and effect diagram

• Identity
• Not
• or
• And
  Constraints in the cause and effect diagram
• different
• or
• only
• requirement
• mandatory
  In terms of reasons, there are mainly 4 Two constraints ：
• E( Mutually exclusive 、 Exclusive )：a、b Two reasons don't happen at the same time , At most one appears
• I( contain 、 or )：a、b、c At least one of the three reasons appears
• O( only )：a、b There must be one of two reasons , And only one appears
• R( demand )：a When it appears b There must be
  In terms of results, there are mainly 1 Two constraints ：
• M( shielding )：a When it appears ,b There must be no ;a When it doesn't appear ,b Not sure

Methods and steps

• Find out all the reasons , The reason is the input condition or the equivalent of the input condition ;
• Find out all the results , The result is the output condition ;
• Clarify the restriction relationship and combination relationship between all input conditions ; What conditions can't be combined , What conditions can be combined ;
• Clarify the restriction relationship and combination relationship between all output conditions ; Which output results cannot be output at the same time , Which output results can be output at the same time
• Find out what combination of input conditions will produce what output results ;
• Draw a cause and effect diagram ;
• Turn the cause and effect diagram into a decision table / Decision table ;
• Design test cases for the situation represented by each column in the decision table ( Each column is a test case ).

Decision table method

Concepts and principles

Definition

Decision table is a tool to analyze and express different operations under multiple logic conditions , It means a form , Used to display conditions and sets of actions caused by conditions .

Principle of method

It consists of five parts ：

• Condition stake ： All the conditions of the problem
• Condition item ： Value combination of all conditions
• Action post ： All possible operations
• Action items ： In the case of each condition value combination , Perform which actions in the action pile
• The rules ： A conditional value combination and its corresponding action combination, a conditional value combination and its corresponding action combination （ That is, a column of condition items and action items in the decision table ） A rule constituting the decision table

Methods and steps

• List all condition piles and action piles ( Input and output );
• Fill in the conditions ( Input item );
• Fill in the action items , Get the initial decision table ;
• Simplify the decision table （ Merge similar rules （ Same action ））

Explain and summarize

Method	Cause and effect diagram / Decision table method
The core	Consider the trust relationship between output conditions and input conditions , Causality
advantage	1. It is helpful to select an efficient set of test cases in a systematic way ;2. By converting specifications into Boolean logical networks , You can point out the incompleteness and ambiguity of the specification
shortcoming	1. For scenarios with a large number of conditional combinations , A large number of test cases will be generated ;2. Usually it cannot generate all the valid test cases that should be determined ;
Applicable scenario	There are multiple controls in the interface , There are combinations or restrictions between controls , Different input combinations will correspond to different output results

But cause and effect diagram and decision table method have many variable values 、 In a scene with a large number of permutations , It will generate very large and redundant test cases , At this time, it is difficult for us to cover all the combined scenarios with full test cases , This is the time for the orthogonal test method to show its magic , Let's study together ~