This is an incomplete collection of frontend testing tips, tricks and tools. It's just the stuff I've found useful over the years. Feel free to suggest more stuff. I'll add it if I like it ;)
- MacOS: Xcode Device Simulator: https://unrealnavigation.com/blog/web-inspector-with-ios-simulator
- Inspector for real iOS devices: https://webdesign.tutsplus.com/articles/quick-tip-using-web-inspector-to-debug-mobile-safari--webdesign-8787
- Inspector for real Android devices: https://developers.google.com/web/tools/chrome-devtools/remote-debugging/
- https://www.browserstack.com/