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Introduction to software engineering

The concept of software engineering

Establish and use sound engineering principles , A series of methods to obtain reliable software that can run effectively on real machines by more economical means .

Three elements of software engineering

1. Software engineering methods
2. Software tools
3. Software engineering process

Common software development models

1. Waterfall model
2. Rapid prototyping model
3. Incremental model
4. Spiral model
5. Fountain model

Software Crisis

20 century 60 years , Computer research and development , function , During maintenance and management , The appearance of a series of serious problems .

The difference between software and program

Software = Program + file = data structure + Algorithm + file .

The difference between program and software is , Software is designed to perform specific functions , A set of command sequences written in computer language to solve a specific problem , It can be understood as a collection of applications . And applications are an integral part of software , It is a necessary element of software .

Feasibility analysis task

1. Technical feasibility analysis
2. Economic feasibility analysis
3. Social feasibility analysis

Requirements analysis 3 A hierarchical

1. Business needs
2. The user needs
3. functional requirement

E-R chart

Data flow diagram

Software design principles

1. modularization
2. abstract
3. Progressive refinement
4. Module independence
5. Information concealment

Modularity and modularity

Modules are the basic components of a software system , Mainly explained by data , Execute statements and other program objects

Modularization is the process of dividing complex software into modules with relatively independent functions and easy to handle

Information concealment

Information concealment refers to the “ Process and data ” Information , Other modules need to be hidden

Coupling and cohesion

Criteria for measuring module independence ： Coupling and cohesion

The criteria for maintaining module independence ： High cohesion and low coupling

Common coupling types and strengths

1. Indirect coupling
2. Data coupling
3. Control coupling
4. Feature coupling
5. Public environment coupling
6. Content coupling

The coupling is gradually enhanced

Detailed design tasks

1. Module algorithm design
2. The internal data structure design of the module
3. Module interface design
4. Other relevant designs
5. Module test case design
6. Prepare detailed design documents
7. Detailed design review and implementation scheme

PAD chart 、 flow chart

Note classification

1. Preambular notes
2. Intermediate notes ( Functional notes )

The purpose of software testing

Find as many errors in the software as possible , Instead of proving the correctness of the software

The concept of acceptance testing

After the software product has completed the function test and system test 、 Software testing activities before product release . It's the last stage of technical testing , Also known as delivery testing .

Basic path testing

Definition ： Basic path testing is also called independent path testing , It is based on the program control flow chart , By analyzing the loop complexity of the control structure , Export the collection of basic executable paths , So as to design the corresponding test case method .

1. According to the result of program design, the control flow chart of program flow chart is derived
   

2. Calculate the loop complexity
   

   The number of regions in the flow graph is equal to the ring complexity
   Flow chart G Ring complexity of V(G)=E-N+2, among ,E Is the number of edges in a flow graph ,N It's the number of knots .

   Flow chart G Ring complexity of V(G)=P+1, among ,P Is the number of decision nodes in the flow graph .

3. Export basic path set , Determine the independent path of the program
   Basic test path :

   • 1-2-6
   • 1-2-3-6
   • 1-2-3-4-2
   • 1-2-3-5-2

4. Design corresponding test cases

The basic path	arr	objectValue	return
1-2-6	[ ]	1	-1
1-2-3-6	[1,2,3]	2	1
1-2-3-4-2	[1,2,3,4,5]	2	1
1-2-3-5-2	[1,2,3,4,5]	4	3

Equivalence class division

Equivalence partitioning is a black box testing technique , The input field of the program is divided into several data classes , Export test cases accordingly .

Divide equivalence class

1. Effective equivalence class : reasonable , Meaningful input data forms a set
2. Invalid equivalence class : unreasonable , Meaningless input data forms a set

The principle of equivalence class division :

1. The input condition specifies the range , Define a valid equivalence class and two invalid equivalence classes
2. The input condition is Boolean , A valid equivalence class and an invalid equivalence class
3. Specify that the input data is a set of values , The program processes each input value separately . Each input value establishes a valid equivalence class , Establish an invalid equivalence class for this set of values
4. Stipulate that the input data must comply with the rules , Define a data valid equivalence class ( Conform to the rules ) and Several invalid equivalence classes ( Breaking the rules from different angles ).
5. Divided equivalence classes Each element is handled differently in the program , Further divide equivalence classes into smaller equivalence classes

Establish test case principles

1. Specify a unique number for each equivalent class
2. Design a new test case , Cover as many valid equivalence classes that have not been covered as possible , Until all valid equivalence classes are overridden

Classification of maintenance

1. Integrity maintenance 50%
2. Adaptive maintenance 25%
3. Corrective maintenance 21%
4. Preventive maintenance 4%

Maintenance side effects

1. Coding side effects : Modifying the code may introduce new errors
2. Data side effects : Modify the data structure , It is easy to cause incompatibility between design and data
3. Document side effects : To data flow , Software architecture , When the module logic is modified , The document should be modified accordingly , Otherwise, errors such as mismatch between document and program functions will occur

The basic characteristics of object-oriented

encapsulation , Inherit , polymorphic

Basic concepts ： object 、 class 、 encapsulation 、 Inherit

Use case diagram 、 Class diagram

Class diagram :

Use case diagram :

Draw a villain

This will cause errors such as mismatching between the document and the program functions

The basic characteristics of object-oriented

encapsulation , Inherit , polymorphic

Basic concepts ： object 、 class 、 encapsulation 、 Inherit

Use case diagram 、 Class diagram

Class diagram :

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Use case diagram :

Draw a villain

Picture source network