Type Hints · interview question

If you wrote a test around optional and collections, what should the test prove first?

Multiple choiceEasychapter-10-curatedpremiumtype-hintsoptional-and-collections

python

from typing import Optional

def normalize_coupon(code: Optional[str]) -> str:
    return code or ""

That the rule behaves correctly at the boundary cases the lesson is trying to make explicit.Keep optional and collections implicit so the script stays short and hope the next engineer infers the rule.Solve the symptom with comments only and avoid changing the code shape around optional and collections.Delay clarity until production traffic reveals the edge case and then patch it under pressure.

Answer and explanation

Correct answer

A. That the rule behaves correctly at the boundary cases the lesson is trying to make explicit.

Why

Good tests make the design safer to change because they lock in the meaningful behavior rather than surface-level implementation details.

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If you wrote a test around optional and collections, what should the test prove first?

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