ClassInitialize

ClassInitialize is a method in the MSTest framework used to perform class-level setup before any tests in a test class are executed. It enables initialization of resources that are shared among all tests in the class, such as database connections, external services, or large test data sets. The method is called once per test class and helps avoid repeating expensive setup code for each test method.

For a method to serve as ClassInitialize, it must be public and static, return void, and accept a single parameter of type TestContext. It must be annotated with the ClassInitialize attribute, and the containing class must be marked with TestClass. If the ClassInitialize method throws an exception, the test class may be skipped or marked as failed, depending on the framework configuration.

ClassInitialize runs before any TestMethod in the class and only once per class, which distinguishes it from TestInitialize that runs before every individual test. It is common to store shared state or references in static fields or properties so that individual tests can access the initialized resources.

A ClassCleanup method, annotated with ClassCleanup, often accompanies ClassInitialize to release the resources after all tests in the class have completed. The TestContext parameter can be used to access deployment items, test run data, or other contextual information that may influence setup. Overall, ClassInitialize provides a structured, efficient way to prepare a test environment at the class level within MSTest.