TestServer in ASP.NET is a programmatic way to create a web server that can be used to run integration or end-to-end tests for a web application. The TestServer simulates the behavior of a real web server, and allows developers to test the web application in a realistic environment, without the need for a physical web server or a browser. The TestServer can be created and configured using the built-in Web Application Factory (WAF) feature in ASP.NET Core. The WAF allows developers to configure the TestServer to use different services, middleware, and settings, depending on the needs of the application. The TestServer can also be used to test the web application against different configurations, such as different databases, different authentication providers, and different hosting environments.
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