MSTest lifecycle

MSTest provides a well-defined lifecycle for test classes and test methods, allowing for setup and teardown operations to be performed at various stages of the test execution process. The lifecycle can be grouped into the following three stages:

• Assembly-level lifecycle
• Class-level lifecycle
• Test-level lifecycle

The execution of the lifecycle events occurs from the highest level (assembly) to the lowest level (test method). The order of execution is as follows:

1. Assembly Initialization
2. Class Initialization (for every test class)
3. Test initialization (for every test method)
4. Test Execution
5. Test Cleanup (for every test method)
6. Class Cleanup (for every test class)
7. Assembly Cleanup

Assembly-level Lifecycle

The assembly lifecycle describes the lifecycle of the entire assembly, which includes all test classes and methods. To manage the assembly lifecycle, MSTest provides the AssemblyInitialize and AssemblyCleanup attributes. To learn more about these attributes, refer to the AssemblyInitialize and AssemblyCleanup documentation.

Class-level Lifecycle

The test class lifecycle refers to the lifecycle of individual test classes within the assembly and can be implemented using the ClassInitialize and ClassCleanup attributes. These attributes allow you to define setup and teardown methods that are executed before and after all tests in a class, respectively. For more information on these attributes, refer to the ClassInitialize and ClassCleanup documentation. The class level lifecycle is only run once per class, regardless of the number of tests in a class.

Test-level Lifecycle

The test level lifecycle is executed for every test method. For parameterized tests, each set of parameters is treated as a separate test method, and the lifecycle is executed for each set of parameters. Test level lifecycle can be grouped into setup, execution and cleanup with setup and cleanup supporting multiple ways to be implemented.

Setup

The setup phase of the test level lifecycle is responsible for preparing the test environment before the execution of each test method. This can be achieved using the TestInitialize attribute or by implementing a constructor in the test class. In the case of inheritance, execution of TestInitialize methods follows the order from the base class to the derived class. If a test class implements a constructor, it is executed before the TestInitialize method. To learn more about the TestInitialize attribute, refer to the test level attribute documentation.

Note

Unlike the class constructor, TestInitialize methods can be async and also support attribute usage such as the TimeoutAttribute.

Execution

The execution phase is the phase where the actual test method is executed. If a test method returns a Task or ValueTask, the test method will be awaited.

Warning

In the case of asynchronous test methods, no SynchronizationContext is provided. This does not apply to UITestMethod tests for UWP and WinUI as they run on the UI thread which has a SynchronizationContext.

Cleanup

The cleanup phase of the test level lifecycle is responsible for cleaning up the test environment after the execution of each test method. This can be achieved using the TestCleanup attribute or by implementing the IDisposable/IAsyncDisposable interface in the test class. If a test class implements IDisposable or IAsyncDisposable, its Dispose/DisposeAsync method is executed after the TestCleanup method. In case of inheritance, execution of TestCleanup methods follows the order from the derived class to the base class. To learn more about the TestInitialize attribute, refer to the test level attribute documentation.

Order

The complete order of the test level lifecycle is as follows:

1. Create instance of test class
2. Set TestContext property if present
3. Run TestInitialize (if implemented)
4. Test method execution
5. Update TestContext with test results (such as Outcome property)
6. Run TestCleanup if implemented
7. Run DisposeAsync if implemented
8. Run Dispose if implemented