Integration tests in ASP.NET Core

Integration tests ensure that an app's components function correctly at a level that includes the app's supporting infrastructure, such as the database, file system, and network. ASP.NET Core supports integration tests using a unit test framework with a test web host and an in-memory test server.

Integration tests evaluate an app's components on a broader level than unit tests. Unit tests are used to test isolated software components, such as individual class methods. Integration tests confirm that two or more app components work together to produce an expected result, possibly including every component required to fully process a request.

These broader tests are used to test the app's infrastructure and whole framework, often including the following components:

Database File system Network appliances Request-response pipeline Unit tests use fabricated components, known as fakes or mock objects, in place of infrastructure components.

In contrast to unit tests, integration tests:

Use the actual components that the app uses in production. Require more code and data processing. Take longer to run. Therefore, limit the use of integration tests to the most important infrastructure scenarios. If a behavior can be tested using either a unit test or an integration test, choose the unit test.

In discussions of integration tests, the tested project is frequently called the System Under Test, or "SUT" for short. "SUT" is used throughout this article to refer to the ASP.NET Core app being tested.

Don't write integration tests for every permutation of data and file access with databases and file systems. Regardless of how many places across an app interact with databases and file systems, a focused set of read, write, update, and delete integration tests are usually capable of adequately testing database and file system components. Use unit tests for routine tests of method logic that interact with these components. In unit tests, the use of infrastructure fakes or mocks result in faster test execution.