How to Create Custom Responses

Environment

Product	Fiddler Everywhere
Product Version	1.0.0 and above

Description

As developers, you frequently need to simulate and test various user conditions to ensure the client-side experience doesn't suffer due to unexpected issues. With Fiddler Everywhere, you could modify the current response (HTML, JS, JSON) previously returned by the server. This article explains how to achieve that via Return manually crafted response or via Choose saved response file... actions of the Auto Responder.

Manually crafted response

1. Open the Auto Responder

2. Create a new rule via the Add new rule button.

3. Add the MATCH condition (e.g., https://www.example.com)

4. Add the ACTION rule. In this case, choose Return manually crafted response from the dropdown and enter the content, as shown below.

   HTTP/1.1 502 Unreachable Server
   Date: Fri, 25 Jan 2013 16:49:29 GMT
   FiddlerTemplate: True
   Content-Type: text/html
   Content-Length: 114
   
   Fiddler: HTTP/502 unreachable server.      
   
   {"errors": "Hey, hey - the server is unreachable at this moment!"}
   

   The newly created rule should look like this:

5. Finally, enable the Auto Responder, activate the newly created rule, and send the request. As a result, the request to https://www.example.com will now return status code 502 with your custom error message. Congratulations - you have just mocked a 502 status code response!

   

DAT Files

Using the above action is handy, but we need a better workflow to automate multiple mock responses. For this reason, Fiddler Everywhere provides the functionality to provide a file (with the mocked response content) via the Choose saved response file... action. The files that will contain the custom response needs to be in DAT format.

A DAT file is a generic data file created by a specific application. It may contain data in binary or text format (text-based DAT files can be viewed in a text editor).

1. Open your favorite text editor.

2. Enter the custom response content. For example:

   HTTP/1.1 403 Access Denied
   FiddlerTemplate: True
   Date: Fri, 25 Jan 2013 16:49:29 GMT
   Content-Length: 520
   
   Fiddler: HTTP/403 Access Denied. 
   

3. Save the file with dat extension . For example save as action-403-status.dat.

4. Add the ACTION rule via Choose saved response file... and in the popup window, choose the newly created DAT file (action-403-status.dat).

5. Finally, enable the Auto Responder, activate the newly created rule, and send the request. As a result, the request to https://www.example.com will now return status code 403 with your custom error message. Congratulations - you have just mocked a 403 status code response while using a DAT file!