Project output doesn't pass test

My project output for the arithmetic formatter project is correct, but it never passes the tests. Here is an example of my project:

I believe this is exactly what the project instructions call for. Why is it not passing the unit tests?

Each failing test should have some information what exactly is different than expected.

Can you help me understand this error please? I don’t know what I’m doing wrong.

The error reads:

+ one output
- other output
? Differences

One and other depend on whatever order inputs got given to the unittest.
However with that in mind: Your output has trailing spaces.

I’m sorry, what do you mean by + “one output” and - “other output.” Does this mean that one of those is right, and the other is wrong, and the difference is indicated by the “?”

Yes ^^
It’s the format such errors are shown in the tests and should help you understand what’s wrong and where to look.

Especially as differences can be trailing spaces, it’s the way to show what’s wrong.