Service Design · interview question

If you wrote a test around dependency injection, what should the test prove first?

Multiple choiceMediumchapter-13-curatedpremiumservice-designdependency-injection

python

from fastapi import Depends

def get_repo() -> OrderRepository:
    return OrderRepository()

@app.get("/orders")
def list_orders(repo: OrderRepository = Depends(get_repo)) -> list[dict]:
    return repo.list_recent()

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

Answer and explanation

Correct answer

C. 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 dependency injection, what should the test prove first?

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