Summary of experience in using.Net test framework xUnit, mstest, specflow

Catalog

Preface

unit testing

Unit test is to give input to the program , Judge whether the output meets the expectation

Not all code can write unit tests

EF unit testing

xUnit and MSTest

Specflow 

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Preface

xUnit and MSTest Both belong to the unit test framework , and Specflow Belong to BDD ( Behavior driven development ) frame .

In fact, the application of the three is very simple , But if you have never been exposed to specific examples , You may be confused from scratch .

I previously wrote an experimental distributed event bus , The above three frameworks are used , Want to learn .NET Students who test technology can go directly to  MaH.EventBus - Repos (azure.com) See the sample .

Another two are recommended .NET Class libraries that are almost necessary for unit testing ：NSubstitute,Shouldly. Both can help us conveniently Mock Interface or data , And making assertions .

unit testing

Brush over Leetcode All of my classmates know that , When we submit our answers , The system will tell us whether it is correct ; If it's wrong , There will be examples of data that cause errors , In fact, behind it is the function of unit testing .

Unit testing is ： A given input , Judge whether the output meets the expectation

For specific algorithms ( Whether business algorithm or mathematical algorithm ) It is very useful to write unit tests with high coverage , It can find problems in the development process , It can also provide assurance for future code refactoring .

People often ignore the role of unit testing , In fact, the value of unit testing also meets the 28 law ,80% Test cases of may be like decorations , After writing, you never need to maintain . and 15% The test cases need to be modified with the change of business code , Perhaps only 5% Unit tests can really play a role in code refactoring .

Of course , There is no castle in the air , You can't build a house with only the second floor but no first floor , You can't just write that “5%” Test cases for .VS perhaps SonarQube Can provide us with unit test coverage analysis , Generally more than 80% Coverage is considered healthy .

Not all code can write unit tests

The object of unit test should be pure function , such as int Add(int a, int b) => a + b; This result is completely determined by the input function . stay VS2022 in , For functions that do not access any instance variables ,VS You will be prompted to change it to static, This kind of function belongs to pure function , It will also be very easy to write unit tests .

But for business projects , Non pure functions are unavoidable , for example , Anything that contains I/O The methods of operation are all non pure functions .

common I/O Operations include database connections , Network request , as well as Task.Delay,DateTime.Now etc. . We should try to encapsulate impure methods in a minimum range .

In addition, methods that rely on specific instances rather than interfaces are also non pure methods .

Unit testing should ensure purity , It means that the execution results must be consistent at any time , So we often need Mock Some data interfaces .

If you use it directly in your code DateTime.Now To make logical judgments , Then you have to refactor the current code , Wrap up the method of getting the current time , It is provided to the specific business logic through the interface , Otherwise, there is no way to write unit tests .

EF unit testing

Suppose you use EF Words , Then it will be very simple to write unit tests , You can use it directly Sqlite perhaps InMemory To create a memory based database , This makes it easy to use real DbContext To write test cases ：

        private static DemoDbContext CreateInMenoryDatabase()
        {
            var connection = new SqliteConnection("Filename=:memory:");
            connection.Open();

            var contextOptions = new DbContextOptionsBuilder<DemoDbContext>()
                .UseSqlite(connection)
                .EnableSensitiveDataLogging()
                .Options;

            var context = new DemoDbContext(contextOptions);

            context.Database.EnsureCreated();

            return context;
        }

xUnit and MSTest

These two project types can be found in VS Found in and created directly , After the creation, we can Test Explorer Find the created project and test cases .

If you are using VS Enterprise version , You can also use Live Unit Testing The function of , It will compile and run unit tests in real time when you write , And a blue or red check mark will be used on the left side of the code line to indicate whether the current line is overwritten , And whether the corresponding test cases are successful .

You can also generate and export containing branches , Test and analysis report of code line coverage and other information .

xUnit and MSTest The biggest difference in use lies in the different characteristics of test case methods , No more details here , Interested friends can go to the preface Code warehouse see . 

Specflow 

Specflow It aims to write test cases in natural language , So that non-technical personnel can understand . But it still needs technical implementation , And compared with unit testing , Often the test process and implementation are more complex .

establish Specflow The project needs to arrive first VS Install in the expansion Specflow plug-in unit

Let's show you Specflow Test Code style , It is recommended that you create Specflow Test Do it according to my project format , Writing Scenario,Steps It will be convenient when .

  

 Specflow It is not only applicable to the test process , For example, based on Camunda BPMN Project created , And business scenarios that contain any process , It can be used for testing in any scenario .

I have this on top Demo The warehouse is right Specflow It's easy to use , Just made a LocalEventBus Usage scenarios of , A is given Specflow The structure of the project .

You can learn the usage of other commonly used keywords by yourself ：

Given、When、Then、And、Background、Examples...

And placeholders that will be used when passing parameters ：

'(.*)'

also Table Type parameters and the use of parsing methods ：

        [Given(@"Hello '(.*)'")]
        public void Hello(string name, Table table)
        {
            var rows = table.CreateSet<T>();
        }

I'm just here to show , No specific explanation .