Is it possible to simulate a multi-monitor setup with only one monitor?

Let's face it: I'm a cheapskate. How else can I put it? OK, yeah, I also have a limited budget. But that's not the point. Here's what the point is:

A lot of people make a lot of ado about multi-monitor setups. Many people have desktops that span two monitors; I've seen some who use a 4 x 4 grid of monitors, for a total of 16 display outputs!

People also tend to expect their desktop and applications to integrate nicely with their multi-monitor setups, at least fairly simple setups (like two or three monitors in a horizontal line). So for example, the desktop and applications should be able to cope with being moved from one monitor with one refresh rate to another monitor with a different refresh rate, and different dimensions to boot.

Or, maybe somebody has a laptop that they use with the built-in monitor when they're traveling, and all other times of the year, they attach it to a nice, big 32" 8K monitor for easy viewing. But every time they do that, their desktop icons shift over unexpectedly, and they have to spend several minutes just moving everything back over! How annoying is that?

I have the skills to write code patches to deal with these issues, but there's one problem: How do I test my code? I don't have a spare monitor I can use for the purpose of testing these things out. And even when I write code that doesn't directly relate to multi-monitor setups -- for example, tracking the width of the Caja "extra pane" -- the upstream developers insist that the code be guaranteed to work even if you move the window from one monitor to another. Fair enough, but how do I test that?

I then thought that, given the Linux philosophy (to tweak is human, to hack is even more so), that there might be a hack or something so that I can simulate a second monitor even if I don't have a real one available for use. The problem is, I've looked around and can't seem to find a good solution.

So, I came here to ask any and all: Does anybody have any suggestions?

Thanks in advance to anybody who can help me.

I think xrandr can create virtual monitors.

(second link explains the numbers, first link does not)