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Overestimated test driven development?

2022-07-29 03:35:00 【Luo Zhaocheng CSDN】

Test-driven development （TDD） It began in the last century 90 years , From time to time, from time to time , Only a few developers are still practicing . From the perspective of software developers , Once again, it helps us define test driven development , Answered many development questions TDD Common fallacies .

author | Tylor Borgeson, Authorized by author
translator | Luo Zhao Cheng
original text | “Test Driven Development is overrated”
This article was first published in CSDN WeChat （ID：CSDNnews）

The following is the translation ：

This is me 「 Popular software development practices 」 The second part of the series , In this series of articles , My plan includes a series of methods for software engineers to improve software development by improving development processes and practices . I was there ThoughtWorks As a software consultant , Now I work in a large retail company in Germany , These methods have been studied and tested in my career .

I once discussed with a customer's developer about software development . Our discussion is a little too much , He mentioned , As a software developer, I'm very lucky , because “ We can cheat the company into paying a considerable income for our basic work ”…… In my submission , Regardless of your programming level , You can't belittle so many software development engineers .

We talked like silk , The discussion gradually goes deep into the practice of agile software development . For the methods mentioned in agile development , They said they could try , Used to improve the current way of working , however , When I mentioned test driven development , They all feel ：

Test driven development doesn't live up to its name .

Hear their comment , I was shocked . meanwhile , They also made me realize , In many people's minds , Test driven development is just a way of agile development practice , In the hearts of more people , It is more like a mirage , It looks beautiful , But it's just like this . In order to let more people know about test driven development , I want to use this article to tell you what is test driven development .

First , Let me define what is test driven development （TDD）.

seeing the name of a thing one thinks of its function ,TDD Is a software development strategy , It guides the development process by writing tests .Kent Beck 2003 In his 《 Test-driven development 》 This concept is mentioned in the book （ translator's note ：Kent Beck, Famous American software engineer and writer , He has made great contributions to software engineering . He is Smalltalk Software developers , A pioneer of design patterns , Supporters of Test Driven Development , It is also one of the founders of extreme programming .）, The implementation of test driven development mainly follows the following three steps ：

Write a failed test case for a small part of the function you want to write .
Realize your functional logic , Let your test case pass .
Refactoring code , Ensure the structure and readability of the code .

This process can be simplified to “ Red , green , restructure ”.

below , I will use the pattern of test driven development , use Python Realize the calculation of oblique boundary value in Pythagorean theorem .

△ Write the test code first , Don't worry about the implementation of the method

△ Run test code , A red error appears

△ Implement code logic , Let the test code pass

△ Refactoring code , Make code logic more elegant

This year is already 2020 Years. ,17 Years have passed , For many developers , The benefits of test driven development are still uncertain , therefore , Most developers have never used TDD .

all the time , I am keen to recommend it to my friends TDD , But there are still many people who choose to refuse , When I asked why , Here are some of the answers I hear most ：

We have a testing team , Writing tests is their job .
When writing test cases , need mock Context object , So we need to spend more time and energy .
It doesn't bring me much benefit .
It's too slow .

below , Let me analyze these answers .

scene 1：“ We have a testing team , Writing tests is their job ”

I always thought , Who wrote the code , Who should ensure that it can work normally , So every time I think of this answer, I feel funny . If you think that only writing logical code is your job , Then your ability will stagnate .

The code written by every programmer should have the following properties ：

Choose and use the right technology stack according to business needs
The code is easy to understand
Testable
Scalable
Simple

In my submission , Give the unit tests that developers can do to the testing department , Is a very unwise act . The testing department has more and more important things to do , Instead of wasting time doing black box tests .

scene 2：“ When writing test cases , need mock Some context objects ”

Your thoughts and feelings of helplessness , I can understand , I used to be like you . There is a way in front of you , This method has three different parameters , And every parameter is an object , meanwhile , Their properties are not empty . Now you need to test this method , Meet the test conditions , A lot of... Needs to be done Mock, This can lead to a lot of extra code written to test a method .

Now? , I have been able to deal with this problem well , And I think it's worth doing these things .

Whenever I think about how to reduce the cost of writing tests , These two things will haunt my mind , Namely SOLID（ translator's note ：S Refers to the principle of single responsibility ,O Opening and closing principle ,L Richter's principle of substitution ,I Interface isolation principle ,D The principle of Dependence Inversion ） And test pyramid .

It's important to note that ,S —— Principle of single responsibility , This principle tells us , A class or a method can only do one thing , This prevents them from having side effects on other parts of the system .

That's true. , The code logic in a company is certainly not as simple as adding two integers , however , If we can simplify the responsibilities of these methods , Then it will become very easy to write tests .

△ Test pyramids , source ：martinfowler

This test pyramid is usually used to measure the priority of different test types .

UI Testing and service testing can take a lot of time , Cost is very high , Unit tests can run in milliseconds , So a system should have more unit tests , Less service testing and UI test . Doing so and DevOps Consistent goals , It can increase the feedback cycle in the whole system development process .

Unit testing requires the new code to be coupled with the original code in the system as little as possible , This makes it easier to code unit tests .

Test driven development is a development mode based on unit testing .

Of course , It's much easier to say than to do . For all types of tests , There will be costs , Unit testing is no exception . If one day , You find that the cost of writing unit tests has increased a lot , You can ask yourself , Are there the following two questions ：

Whether the current test is within the scope of unit test , Whether it is necessary to upgrade to the scope of service testing ？
Is your code structure reasonable , Whether your classes and methods have a single responsibility ？

If you are writing unit test code , Need to constantly invest a lot of costs , That means , There are some problems with your code , You need to refactor it , Make the code structure clearer .

scene 3：“ It doesn't bring me much benefit ”

It's funny , Most people who say so , Are people who don't really use the test driven development mode . It's on paper , We must know that we must do it .

below , I'll show you how to use TDD Two big benefits ：

The first one is obvious , according to TDD The definition of , Before writing real logic code , All need to be tested before writing , The code produced in this way is self-test . just as Martin Fowler（ translator's note ：Martin Fowler, Famous British Software Engineer , He is also a writer and internationally renowned speaker in software development , Focus on object-oriented analysis and Design , Unified modeling language , Domain modeling , And agile software development methods , Including extreme programming .） said ：

If your code is self testing , So as long as you run a series of automated tests against the code , Wait until it passes , You can guarantee that your code will not show any real defects .

let me put it another way , Your code can run normally according to the process you defined in the test code .

Unit tests are very useful , It can make you confident in your code . In refactoring , It can find the problems caused by refactoring at the first time , also , And unit testing can also let you know whether there is Bug .

Self testing code can benefit the whole team in the process of development and integration .

Use TDD Another benefit is , It allows developers to write logical code before , Think carefully about what kind of code to write , And how to write code . Thinking before coding , It allows developers to really go deep into business needs , Consider possible boundary problems and possible challenges , This process is time-consuming and painful , But it's not a waste of developer's energy . More Than This , Writing the test first , It will also encourage developers to write code from the beginning , Consider the design and architecture of the system , This can greatly improve the system scalability .

scene 4：“ It's too slow ”

In my experience , People who have this idea , Most of them are those who try to use TDD People who , However, they use the previous development mode , Write code first. , Finally, let's write the test . This is also the reason why most developers cannot adhere to the implementation TDD One of the most common reasons .

I deeply understand the thoughts of these developers , Before writing code , Think first , Then spend time writing test code , Compared with not writing tests , It really takes more time . occasionally , simulation mock It is not only troublesome to generate effective data in the scene , It will also make people feel very depressed .

Although I say a lot TDD The advantages of , But it doesn't help , Many companies' business departments take the time of development and delivery as a measure , The whole team is working hard to develop new requirements .

In Agile Development , There are four key indicators to measure software development （ I often refer to these indicators ）, Two of them are change failure rate and deployment frequency . As I said above , Suppose the system uses TDD structure , When you submit code , The whole team will know whether the modification of the code will lead to the collapse of other functions of the system , At the same time, it can improve the efficiency Bug The speed of being found . The locality of unit testing , Developers can quickly find the cause of the problem . So back and forth , The possibility of causing abnormal functions will be smaller and smaller , Thus reducing the change failure rate .

The code passed unit tests , It can also make us have stronger confidence in the robustness of software functions , The whole team can decide whether to deploy through the unit test results , Anyone can deploy on demand .

《 Phoenix Project 》 Four types of work are listed in , One of them is “ Unplanned work or fire fighting work ”. This kind of work is usually caused by mistakes , Developers must stop working and give priority to . Self testing code can minimize such errors , That means , It can help us minimize “ Unplanned work or fire fighting work ”, It can also maximize the satisfaction of developers . Happy development is good development .

When developers don't have to worry about online problems , They can focus more on the development of new functions . Before they write code , Have considered how to write code , Can write in line with SOLID Code for principles . The code will be refactored constantly in the development , Technology debt will also be minimized . The team is confident in code quality , It can be deployed online at any time , This will make the whole team run faster .

Everything is difficult at the beginning , Like other tools and practices , At the beginning of test driven development , It may be very uncomfortable , And it will reduce your development efficiency , however , Just like the father of continuous delivery Jez Humble said ：

Do things that make you feel painful early and often .

Now start your test driven development journey , Until it makes you feel comfortable . Thanks for reading .

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