Unit test concept and purpose

Why do we need unit testing ？

   Imagine an old system that has been used for more than ten years , When you need to modify the code , The developer in charge of the modification has just taken over , In this case , Presumably most people dare not modify the original code , Because it is often changed A Code at , The results showed that there were hundreds of thousands of miles apart after the launch Z The function is affected .

   Why does this happen ？ The essential reason is that the developers do not have enough knowledge of the system code ？ Obviously not . A system developed by many people , Often the style is not uniform , The internal calling relationship is complicated . We need a means , That is, the code style can be standardized at a certain level , More importantly, you can find the impact of code changes on functions as soon as possible .

   unit testing , Formal means , It can help developers and testers improve code quality 、 Find code problems earlier .

What is unit testing

   unit testing （unit testing）, It refers to the inspection and verification of the smallest testable unit in the software . as for “ unit ” Size or range of , There is no clear standard , Mainly based on the language used . If you are using functional programming , A unit most likely refers to a function . Your unit test will call this function with different parameters , And assert that it returns the expected result ; In object-oriented languages , Go to the next method , Up to a class can be a unit , From a single method to an entire class can be a unit .

   Unit testing in a broad sense , There are three aspects ：

• 1. Code day reading （Code review)： Observe whether the input parameters of the code are verified 、 Whether the algorithm is correct 、SQL sentence 、 Exception handling and so on ;
• 2. Static code analysis （Static analysis)： Bring in assumed parameters , Infer whether the code can execute normally , Whether the analysis results are correct ;
• 3. Dynamic code analysis （Dynamic analysis)： By writing test scripts , Actually call the tested code , To verify code execution ;

   The first two depend mainly on the human brain , It's limited . So when we talk about unit testing , It mostly refers to the third way of dynamic code . Dynamic code is not only more efficient 、 The results are more accurate , And can be preserved for a long time 、 Multiple runs , You can run away every time you submit code , Test and verify the new functions , It can also return to the original functions .

Who does the unit test

   There are two options ： Developers do or The tester does

   Developers do unit tests ：

• advantage ： Stronger development and coding ability , Have a better grasp of the system , So writing test scripts is faster ;
• Inferiority ： Weak test concept , The coverage scenario is not comprehensive ; Test your own code , There is the possibility of lazy water ;

   Testers do unit tests ：

• advantage ： Be able to design more comprehensive test cases , Higher coverage ; More strictly , Put an end to water drainage ;
• Inferiority ： Coding ability is weak , The efficiency of test script writing is low ;

   My point of view is that unit tests are done by testers . First, in daily work , Discover and develop unit test and waterproof verification , To increase test coverage , resort to every conceivable means , Coverage data is up , But in fact, it is not really detected . Then I think highly of TDD Pattern , stay TDD In the mode of , The tester writes the test case first , Developers will implement , This model can not only make the requirements more explicit 、 Reduce late requirement modification , And the test left shift is realized , Better guarantee code quality .

   Unit tests are done by testers , It is not only a test of the coding ability of testers , It is also a test of the workflow . For most people who are used to traditional waterfall programming IT people , Pair programming 、 Test driven development needs a clear feasibility precedent and adaptation process , I'm also doing exploratory practice in the company's microservice project .

The purpose of unit testing

   Unit tests can help us solve 、 Prevent certain problems , But that alone is not enough , Is the value of unit testing big enough for us to do it ？ For businesses , Benefits , Always first . Unit testing is popular in the enterprise , Its primary purpose , Is to improve the efficiency of the enterprise ！

   How can unit testing improve efficiency ？ Most people have their first feelings about unit testing , It will increase the workload of developing code , before 7 The need to be able to develop in the future , With unit testing, you may have to 14 days .

   But we have to look at it as a whole , The life cycle of software goes far beyond “ Development ” This one link . Although the introduction of unit testing increases the cost of development , But from “ Test pyramids ” In theory , The sooner you find an error , The lower the cost of correction , So the more tests at the bottom , On the contrary, the more efficiency can be improved ！