This seems to be well implemented. It's actually running the commands and then checking for the necessary post conditions.

The command editor has serious problems. When you try to insert a character into the middle of a command line, everything to the right disappears. I'm referring here to a command line recalled with up arrow. I can't reproduce this on the current line because I can't use the left arrow key at all to move left. Left arrow is treated as submitting the command for testing.

This would be a good area to concentrate on.

I'm currently on mobile, Android phone with Chrome, using Hacker's Keyboard. Maybe on desktop things are different.