Add unit tests for pure functions

[TheTrustedAdvisor]

Problem

The project has zero test coverage. However, several functions are pure (no I/O, no side effects) and immediately testable:

• parse_weekplan_html(html) — HTML → structured data
• parse_favorites_html(html) — HTML → structured data
• parse_shopping_ingredients(shopping_data) — dict → ingredient list
• format_time(seconds) — int → string
• seconds_to_minutes(seconds) — int → int
• format_cookie_header(cookies) — dict → string
• extract_category_name(recipe_data, category_id) — dict → string

Proposed Solution

Add a tests/ directory with pytest tests:

# tests/test_parsing.py
def test_format_time_minutes():
    assert format_time(1800) == "30 Min"

def test_format_time_hours():
    assert format_time(5400) == "1h 30min"

def test_format_time_none():
    assert format_time(None) == ""

def test_parse_shopping_deduplication():
    data = {"recipes": [
        {"title": "R1", "recipeIngredientGroups": [
            {"ingredientNotation": "Salz", "quantity": {"value": 1}, "unitNotation": "TL", ...}
        ]},
        {"title": "R2", "recipeIngredientGroups": [
            {"ingredientNotation": "Salz", "quantity": {"value": 2}, "unitNotation": "TL", ...}
        ]},
    ]}
    ingredients = parse_shopping_ingredients(data)
    salt = [i for i in ingredients if i["name"] == "Salz"]
    assert len(salt) == 1
    assert salt[0]["quantity"] == 3

Impact

• Effort: Low (pure functions, no mocking needed)
• Value: Catches regressions in the parsing logic, enables confident refactoring