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How to Mock a Function Call in Python with unittest.mock

Use unittest.mock.Mock to wrap a function and spy on its call count and arguments in Python.

import random
from unittest.mock import Mock, patch


def select_n_plus_one(numbers: list[int]) -> int:
    """Return the first number that appears more than once, if any."""
    seen = set()
    for num in numbers:
        if num in seen:
            return num
        seen.add(num)
    return -1


def detect_mock(se…

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