In 2019, I worked on the Metro app's menu feature, which was a great experience. Although I didn't have the resources available for customer usability testing, I completed it in just one sprint, which was challenging but rewarding. 
I understand the importance of conducting guerrilla testing, so I recommend crowded areas such as canteens 🍔 as ideal locations for you to try it out.
I tested a high-fidelity prototype that the filters implemented as chips below the navigation bar. We wanted to see whether the users recognise the chips and how they drill down the menu items.
Participants were asked to "Please list the various types of Wurst & Schinken products" during a test. Most contributors, precisely 9 out of 11, preferred to use the search bar to locate and list these items. The search bar was a convenient and efficient way of finding the desired products.
During testing, 7 out of 11 participants could quickly find the correct category for the items. However, the other 4 participants struggled a bit, indicating a need for improvement. After another iteration of testing, I refined the category drill down and finalized the process in one sprint 🏁

Prototype not found. Added real app video.

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