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 on lower level Servlet concerns cannot be directly tested with MockMvc.
However, since mocking occurs at the Spring MVC layer, code that relies on lower-level Servlet container behavor 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.
