Create tests for the `addition` function

## Task

Create the test for the addition function. This can be seen in `test_operations.py` with the function called `test_addition`.

## Acceptance Criteria

The test should fail if addition is wrong by mathematical logic
The test should succeed if addition is correct by mathematical logic

Open test_operations.py and locate test_addition. Run the existing test suite first to see the current behavior, then create the test so it fails for mathematically incorrect addition and passes for correct addition. Done means the test reliably distinguishes correct from incorrect addition.

Written by the indexing model from the issue text.