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Improving Subjective Testability with Fiddler

Note: There are prerequisites for attending this workshop. Please see the prerequisites section.

Most modern software is built as a communication between a local computer and a server. Web debugging proxy software such as Fiddler allows testers to take an active role in this communication. This workshop will teach participants how to see what information is being exchanged, as well as how to take control over what is being said - in other words, improving Visibility and Controllability that is available to the tester.

Fiddler is a free web debugging proxy, which can be used regardless of what other software you are using. The instructor is not associated with Fiddler or the company that is offering it in any way. Some other alternatives will also be mentioned.


Short introduction to http requests and the role of proxy servers. Several sets of live demos followed by open activity. Participants will be asked to form small groups in order to enable peer to peer learning and interaction. Participants are encouraged to share their own unique contexts, so that we may figure out how they could put what they have learned to use right away.

Key takeaways:

  • Learn to capture traffic between your app and the server.
  • Learn to change the communication that takes place.
  • Hear some of my favourite use cases that helped me supercharge my testing.



Bring a windows laptop, ideally with Fiddler installed. Fiddler is not guaranteed to work on Macs.