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Testing Rest APIs Using Fiddler

by (October 8, 2015)


Fiddler is considered to be a really powerful web debugging proxy which logs all HTTP(S) traffic between the computer and the internet. It allows you to inspect traffic, set breakpoints, and lets you “fiddle” with the incoming or outgoing data. It helps the developers in identifying potential scalability issues and eventually, evaluates application performance in various production scenarios. Developers are able to configure multiple load test parameters like number of test iterations or test execution time, think times, virtual users, load patterns, web browsers, network type and warm-up times. When it comes to debugging HTTP on your local machine, Fiddler is the best. It can intercept HTTP requests and responses. Fiddler has a very powerful IDE that adds a lot of extra advanced features which further, helps you to monitor and troubleshoot your HTTP calls.

Testing Rest APIs Using Fiddler

  • REST is defined as a set of architectural principles by which you can design Web services that focus on a system’s resources including how resource states are addressed and transferred over HTTP, by a wide range of clients, written in different languages.
  • REST, typically, runs over HTTP. The idea is that rather than using complex methods, simple HTTP request are used to make calls between the machines.
  • RESTful applications use HTTP requests to post data (create and/or update), read data (e.g., make queries), and delete data.
  • This basic REST design principle establishes a one-to-one mapping between create, read, update, and delete (CRUD) operations and HTTP methods. According to this mapping:
    • To create a resource on the server, use POST.
    • To retrieve a resource, use GET.
    • To change the state of a resource or to update it, use PUT.
    • To remove or delete a resource, use DELETE.

To learn more, download this document on Testing REST APIs using Fiddler, which explains Fiddler in more detail, how to test REST APIs using Fiddler, Testing Get Calls and Testing Post Calls through real experience, while working on a project.


Salu K.S.

Application Testing Engineer, RapidValue Solutions

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