This library adds Assert functions which are only checked in debug mode (that is, in the editor).
This lets you create reliable code which has no performance impact once the game is released.
This is because C# has an attribute which can actually remove code if DEBUG isn't defined. It completely disappears.

For a taste about defensive program, please watch the ~9 minutes after this timestamp in this video: https://youtu.be/oitYvDe4nps?t=210
Emphasis on the part at 8:40.

The issue which inspired this project: https://github.com/Facepunch/sbox-public/issues/291
The source code is available at https://gitgud.io/nixx/sbox-debug-assertions

Note: The assertions sit in the Quality.Diagnostics namespace, in case s&box ever add their own.