Testing within a mocked environment is usually faster than running with a full Servlet container.
However, since mocking occurs at the Spring MVC layer, code that relies on lower-level Servlet container behavor cannot be directly tested with MockMvc.
However, since mocking occurs at the Spring MVC layer, code that relies on lower-level Servlet container behavior cannot be directly tested with MockMvc.
For example, Spring Boot's error handling is based on the "`error page`" support provided by the Servlet container.
This means that, whilst you can test your MVC layer throws and handles exceptions as expected, you cannot directly test that a specific <<#boot-features-error-handling-custom-error-pages, custom error page>> is rendered.
