Why Your ASP.NET Core Tests Suddenly Trigger Azure Authentication

Running integration tests in ASP.NET Core feels simple—until your tests start calling Azure without permission. This usually happens when you use WebApplicationFactory<T> to spin up a real application host. The test doesn’t run only your code; it runs your entire application startup pipeline.
That includes:

• Configuration loading
• Dependency injection setup
• Background services
• Azure clients and authentication providers

If your app registers Azure services during startup, they will also start up during your tests. And if the environment lacks proper credentials (which test environments usually do), Azure returns errors like:

• AccessDenied
• Forbidden

This can be confusing because unit tests work fine. But integration tests behave differently because they load real startup logic.
The issue isn’t Azure being difficult—it's your tests running more than you expect.

Understanding this is the first step to diagnosing configuration problems before Azure becomes part of your test run unintentionally.