Using Dynamic Responses feature, Mocklets allows you to set up multiple responses for your APIs and select an active one on-the-go to test your web/app across various scenarios, which cannot be simulated with your real server environment.
Each response can have its own set of headers(Content-Type, Content-Encoding), response delay and response body.
This feature allows development as well as QA teams to test their applications, across various scenarios starting from the development phase, resulting in a much more robust and stable product.
If you want your API to return any specific response, which is not currently active, you can do that using query params also. Please refer this link for more.