In this post, I will explain the basics of xUnit and how to write unit tests with it. Net framework and was written by the inventor of NUnit v2. Net core as the default testing framework and its major advantage over NUnit is that every test runs in isolation, which makes it impossible that test influence each other. Keep in mind that the tests are only for the demonstration of xUnit. The tests are barely useful. For each class I want to test, I create a separate class to which I add tests in the name, for example, if I want to test the Employee class I name my test class EmployeeTests.
To create a test method, you only have to add the Fact attribute to the method. You can run the test and if the constructor of your Employee class sets the salary tothe test will pass. I like to name the object I want to test testee. Another common name is sut which stands for system under test. In the intro, I mentioned that every test runs in isolation in xUnit. This is done by creating a new instance for each test.
Therefore the constructor is called for each test and can be used to initialize objects, which are needed for the tests.
Getting Started with xUnit.net
Sometimes you have to do some cleanup like a database rollback or deleting a file after the tests were executed. Like the constructor, this can be done in a central place for all tests. To do that implement the IDisposable interface and implement the Dispose method. This method is called every time a test is finished.
Often you want to execute a test with different parameters, for example, if a valid age for your employee has to be between at least 18 and maximum 65 years, you want to test the edge cases 17, 18, 65, Additionally, you might test negative numbers.
You could write several asserts but this would be a lot of typing and not really practical. The solution for this is the Theory attribute in xUnit. A Theory allows you to pass values from different sources as parameters to your test method.
With the InlineData attribute, you can add values for the parameter. Executing the same method with several input variables. To ignore tests, add the Skip attribute and provide an info message. I barely use this feature but sometimes you want to group certain tests together. This can be for example all tests from one class and only some tests from another class. To do that use the Trait attribute and provide a name and category.
You can apply this attribute to a class or to a single test.
An Introduction to XUnit, Moq and AutoFixture
Applying the Trait attribute to a test method. Applying the Trait attribute to a test class. If you run the tests and group the output by category, all traits with the same category will be grouped together. By default, no output is generated when a test finished. For reporting reasons, it can be useful to add some information on what the test did to the output of the test. This can be done with the ITestOutputHelper.
Pass it as parameter in the constructor of your test class and initialize a private field with it. Creating a custom message for the test result.It is common for unit test classes to share setup and cleanup code often called "test context". When to use: when you want a clean test context for every test sharing the setup and cleanup code, without sharing the object instance.
This makes the constructor a convenient place to put reusable context setup code where you want to share the code without sharing object instances meaning, you get a clean copy of the context object s for every test that is run.
For context cleanup, add the IDisposable interface to your test class, and put the cleanup code in the Dispose method. This structure is sometimes called the "test class as context" pattern, since the test class itself is a self-contained definition of the context setup and cleanup code. You can even name the test classes after the setup context so that it's easier to remember what your starting point is:.
At a high level, we're writing tests for the Stack class, and each context is a Stack in a given state. To reflect this, we've wrapped all the testcontext classes in a parent class named StackTests. When to use: when you want to create a single test context and share it among all the tests in the class, and have it cleaned up after all the tests in the class have finished. Sometimes test context creation and cleanup can be very expensive.
If you were to run the creation and cleanup code during every test, it might make the tests slower than you want. You can use the class fixture feature of xUnit. We already know that xUnit. When using a class fixture, xUnit. Just before the first tests in MyDatabaseTests is run, xUnit.
For each test, it will create a new instance of MyDatabaseTestsand pass the shared instance of DatabaseFixture to the constructor. Important note: xUnit. It will do this whether you take the instance of the class as a constructor argument or not. Similarly, if you add the constructor argument but forget to add the interface, xUnit. If you need multiple fixture objects, you can implement the interface as many times as you want, and add constructor arguments for whichever of the fixture object instances you need access to.
The order of the constructor arguments is unimportant. Note that you cannot control the order that fixture objects are created, and fixtures cannot take dependencies on other fixtures. When to use: when you want to create a single test context and share it among tests in several test classes, and have it cleaned up after all the tests in the test classes have finished. Sometimes you will want to share a fixture object among multiple test classes. The database example used for class fixtures is a great example: you may want to initialize a database with a set of test data, and then leave that test data in place for use by multiple test classes.
You can use the collection fixture feature of xUnit.Some of these concepts are implemented differently enough that automating the migration from one to the other would be very difficult if not impossible. However, some of it really is that simple. Before we look at the difficult examples, I thought it would be useful to illustrate how some of the simple concepts map from MSTest to XUnit using an example 2. Clearly, I cheated by not actually making the tests do anything, but the content of the test methods is mostly irrelevant; you set some stuff up, you do something, and you assert a result—it's all the same regardless of the test framework.
However, this is a simple example of a test class written for the MSTest framework. There are attributes to tell the framework that the class is a test class, which methods inside of it are test methods, and which methods should be called before and after each test. In this case, our test initialization creates a stream, which is then disposed of in the cleanup method; each test method would get sandwiched in the middle.
Overall, I love how the XUnit syntax works with C syntax and. NET idioms in declaring tests. Not only does this reduce the ceremony around defining tests by reducing the various decorators, but it also allows for cleaner coding practices. For example, we can now correctly mark our memory stream member variable as readonly. By relying on C syntax and standard interfaces in this way, the lifecycle of a test is clearer too; XUnit will construct and dispose the class for each test in the class, making it easy to see how each test will run.
This idiomatic way of declaring tests allows for separation of concerns, keeping test classes light and focused. Regarding your 3rd comment.
Since the test runner uses reflection to find the tests it can reduce that time by not checking every method of every class — instead just the methods in a class marked with a specific attribute. Also don't underestimate group mentality — this is the way it's usually done throughout many unit testing frameworks and programming languages. Great series. I've been struggling on how to implement setup and cleanup after each test. Thanks a lot. I guess you didnt actually understand what TestInitialize actually does to thing that a constructor can be a replacement.
The XUnit2 documentation even calls out this correlation:. Is it perhaps plausible that you may not understand what a constructor does in XUnit2 such that you do not think it is an appropriate replacement for MSTest's TestInitialize? What if we need to initialize once for all testes? Yes, you can definitely do that. Checkout this post on ClassInitialize and sharing data. Your email address will not be published.
This site uses Akismet to reduce spam. Learn how your comment data is processed. The class no longer has an attribute. XUnit knows the class is a test class because it contains tests 3. Thank you for your comment, Paco. Leave a Reply Cancel reply Your email address will not be published.In this article, we will demonstrate getting started with xUnit. Note: The examples were done with xUnit. The version numbers, paths, and Visual Studio UI may differ for you, depending on which version you're using.
Let's start by creating a class library project, targeting. NET 4. This package xunit is what's called a meta-package ; that is, it's a package that exists just so you can get references to several other packages.
In particular, it brings packages that include the core unit testing framework and the assertion framework. If you open packages. When creating a new project with Visual Studioyou may not end up with a packages.
That's okay: newer versions of Visual Studio place the NuGet package references directly into your. The advantage is that you not only have one fewer file, but you also only have packages listed for which you've taken direct references. That makes it easier to differentiate between the packages you've chosen to install and the dependencies they bring with them. When you created the project, Visual Studio automatically created a file named Class1. Inside this class, add a couple tests:.
Build the solution to ensure that the code compiles. Now that you've written the first test, we need a way to run it.
Let's install the NuGet package with the console runner. This time, you're going to search for and install a package named xunit. Unlike the previous package which added references to the unit testing frameworkthis package is what's known as a solution-level package.
Instead of having assemblies to reference, it adds some tools in your solution folder. We will use one of these tools—the console runner—to run your unit tests. Open a command prompt or PowerShell command window. In the window, navigate to the root folder of your solution.In this article, we will demonstrate getting started with xUnit.
Note: The examples were done with xUnit. The version numbers, paths, and JetBrains Rider UI may differ for you, depending on which version you're using. In our example, we have a solution with a single project called Sandbox, which has a class that implements a primitive calculator. To test our calculator, let's start by creating a project for our xUnit. Choose the Unit Test Project template targeting. NET 4. When you click Createthe new test project with all necessary configurations and references will be added to our solution.
When you created the test project, JetBrains Rider automatically created a file named Tests. Let's edit the test stub to target our calculator class:. Note: If you copy-pasted the above code to the Tests. Build the solution to ensure that the code compiles.
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Now that you've written the first tests, let's run them. You can click the unit test icon next to the test class and choose Run All to run all tests in that class. Rider will start the tests and bring up the Unit Tests window where you can see test status and results.
As expected, the PassingTest has passed and the FailingTest has failed. You may have wondered why your first unit tests use an attribute named [Fact] rather than one with a more traditional name like Test. When describing the difference between facts and theories, we like to say:. So you will need a theory to write a data-driven test — a test that can work with multiple data sets. For example, we can test our calculator with different input values and expected sums. Note that feeding an incorrect sum value into such test would cause it fail, and not because the calculator or test is wrong.
Let's add a theory to our existing facts including a bit of bad data, so we can see it fail :. This time when we run our tests, we see a failure for our theory when it was given a sum of 5 for 2 and Although we've only written 3 test methods, the test runner actually ran 5 tests; that's because each theory with its data set is a separate test.
Note also that the runner tells you exactly which set of data failed, because it displays the argument values. As you write more tests, you may end up having a lot of files or directories in your test project, or you can even have multiple test projects in your solution. In such situation, using editor controls as demonstrated above will not be the most convenient way to run multiple tests. Instead, you can locate a solution, project, or any node containing unit tests in the Solution Explorer, right-click on it and choose Run Unit Tests.
Or alternatively, you can browse all tests in the solution on the Explorer tab of the Unit Tests window and run tests from there.When it comes to unit testing.
NET applications, there are various frameworks, test runners and libraries available. Teams often undergo meticulous efforts to write the right testing strategy for their applications. These technologies fulfil our needs for writing test suites that are much easier to understand, are robust and are quicker to write.
XUnit is a.
NET test runner created by the developers that built NUnit. The features that XUnit has to offer came from the lessons learnt from using NUnit 2. They aimed at improving test isolation and trying to codify a set of rules to establish a testing standard. Start by creating a new class project and installing XUnit by running install-package xunit in the package manager console. Various other runners are readily available. The setup code in XUnit is much more succinct than that found in NUnit test suites.
Tests can be broken down into Fact or Theory. Facts are always true, testing the invariant conditions. Theories are only true for certain sets of data. To improve test isolation, it is recommended that context is not shared between tests. If you still want to share context between tests, then you can do so in two different ways.
In more complex scenarios, developers often create fixtures several times per file catering the needs of their test suites, however using the above example ensures that fixture is created once per test file. This is extremely useful for when the creation of the fixture is expensive.
These are some of the main differences that we found moving from NUnit, their documentation is a great resource to begin with. Moq was chosen as the mocking framework for its simplicity, providing a clean api for mocking and verification.
AutoFixture supports it out of the box and its simplicity means it has a very fast learning curve. To get started with Moq run i nstall-package moq in the package manager console. The following example shows a product service with one dependency of IDatabase.
IDatabase is used for interacting with a data store via commands and queries. To test this class I have mocked the interactions with the data store. Moq allows you to parameter match using the It class. This allows us to assert that our system under test is calling out to its dependencies in the way we expect, with the parameters we expect.Unit testing .NET Core Project using xUnit in Visual Studio 2017 - xUnit 101
This is a very brief example of how we can use Moq for setup and verification. Further examples of its capabilities can be found in their documentation.
The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. This question is about the unit testing framework xUnit. I need to run some code before any test is executed, and also some code after all tests are done. I thought there should be some kind of attribute or marker interface to indicate the global initialization and termination code, but couldn't find them.
Alternatively, if I invoke xUnit programmatically, I can also achieve what I want with the following code:. However, it is easy to create one. Just create a base test class that implements IDisposable and do your initialization in the constructor and your teardown in the IDisposable. Dispose method. This would look like this:. However, the base class setup and teardown code will be executed for each call.
This might not be what you want, as it is not very efficient. This will result in the constructor of TestsFixture only being run once for every class under test. It thus depends on what you want exactly to choose between the two methods. This is in line with the answer from Geir Sagberg, and gives good skeleton implementation to illustrate what it should look like.
Collection Fixtures When to use: when you want to create a single test context and share it among tests in several test classes, and have it cleaned up after all the tests in the test classes have finished. Sometimes you will want to share a fixture object among multiple test classes. The database example used for class fixtures is a great example: you may want to initialize a database with a set of test data, and then leave that test data in place for use by multiple test classes.
You can use the collection fixture feature of xUnit. Create the fixture class, and put the the startup code in the fixture class constructor. If the fixture class needs to perform cleanup, implement IDisposable on the fixture class, and put the cleanup code in the Dispose method.
Create the collection definition class, decorating it with the [CollectionDefinition] attribute, giving it a unique name that will identify the test collection. Add the [Collection] attribute to all the test classes that will be part of the collection, using the unique name you provided to the test collection definition class's [CollectionDefinition] attribute.
If the test classes need access to the fixture instance, add it as a constructor argument, and it will be provided automatically. Here is a simple example:. Test collections also influence the way xUnit. For more information, see Running Tests in Parallel.
It's a nuget package and when you install it it adds a new file called ModuleInitializer. There is one static method in here that gets weaved into the assembly after build and is run as soon as the assembly is loaded and before anything is run. I use this to unlock the software license to a library that I have purchased.
I was always forgetting to unlock the license in each test and even forgetting to derive the test from a base class which would unlock it. The bright sparks that wrote this library, instead of telling you it was license locked introduced subtle numerical errors which causes tests to fail or pass when they shouldn't. You would never know if you had correctly unlocked the library or not. So now my module init looks like.
Learn more. Ask Question. Asked 7 years, 5 months ago.