Opinions on inverting tests

Does inverting a test work? Could the line that shows up (if one does) still be an indent or does it mean it has colour if a line is showing up after it's inverted?

Minefield 🤯

This is my cheap internet strip from today, 10dpo. I did one yesterday and a frer which were both negative. I'm trying to wait a few days before using my second frer...