Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the mutation and copying bugs pattern
Assignment does not copy, a shallow copy still shares its contents, and mutating methods return None.
What went wrong: append() always adds exactly one item. Given a list, it adds the whole list as one item.
The fix: cart.extend(new_items)
Remember: append() adds one item. extend() adds each item from another list.
The pattern behind it: mutation and copying bugs.
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<iframe src="https://trybughunt.com/embed/61a47b8e-175e-4771-8dc5-765a25fe58ec" title="Debugging challenge: Adding two items puts a list inside the list" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe>
<p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/61a47b8e-175e-4771-8dc5-765a25fe58ec">TryBugHunt</a></p>