tdd-guard

### Code Review Feedback

**Code Snippet:**
```python
def add(a, b):
    return a + b
```

**Feedback:**
- **Test Coverage:** The function `add` lacks corresponding unit tests. Ensure that there are tests verifying its behavior for various inputs, including edge cases (e.g., negative numbers, zero).
- **Improvements:** Consider implementing tests like:
  ```python
def test_add():
    assert add(1, 2) == 3
    assert add(-1, 1) == 0
    assert add(0, 0) == 0
  ```
- **Recommendation:** Enforce writing tests before implementing the function to adhere to TDD principles.