How can I get Firefox to use my proxy for connections to localhost?

Question

I'm writing some proxy-related software and I want to test it using Firefox on Linux (Ubuntu).

My proxy is running at localhost:8080 and I've pointed Firefox at it. It works fine for external websites, but when I attempt to access my test application at localhost:8090, I notice the proxy is bypassed.

In the Connection Settings dialog, there is a "No Proxy for" section, but it's empty already.

How can I force Firefox to push all traffic through my proxy?

I've seen similar questions that suggest adding a synonym for localhost (say local) in my /etc/hosts file. This works at the Firefox end, but it's a difficult solution because my proxy (and several related services) are running inside Docker and it's proving painful to dynamically get my hosts IP address to add a similar local definition inside my proxy container.

Answer 1

In typical fashion, I found an answer mere moments after posting this.

The FoxyProxy add-on allows me to force all traffic through a proxy, including localhost.