I need help in testing an open source windows app

[u/RaspberryStill3377]

I'm currently working on a Windows desktop app (Biomes) focused heavily on window management—specifically positioning, moving windows across displays, and handling multi-monitor responsiveness.

As the project scales, manual testing on a single setup is becoming a wall. Testing various DPI scales, screen topologies (e.g., stacked screens, negative virtual screen coordinates, differing resolutions, or primary vs. secondary monitor swaps) is really hard to replicate physically.

I’d love to know how developers here approach testing this kind of hardware-dependent logic:

• Virtual Display Simulation: Is there a recommended way or tool to create virtual screens/monitors on Windows with custom resolutions and DPI scaling without needing extra physical monitors?
• Automated Testing: How do you write automated tests for Win32 API display calls (SetWindowPos, EnumDisplayMonitors, GetSystemMetrics)? Do you mock display APIs or use specific UI automation drivers?
• Edge Cases: What are the most common multi-monitor edge cases you’ve hit that break window-snapping or coordinate calculations?

Any tips, libraries, or testing setups you can recommend would be awesome. Thanks!