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python - 迭代 Mock 返回值

问题描述

我正在尝试模拟返回列表的方法。设置后return_value，它仍然返回一个 Mock 对象而不是列表，所以我不能迭代那个对象。

我要测试的功能示例：

def func(db_engine):
    query = f"SELECT * FROM table"
    query_result = db_engine.execute(query).fetchall()
    extracted_val = []
    for res in query_result:
        extracted_val.append(res[1])
    return extracted_val

测试示例：

def test_fun():
    query = MagicMock()
    query_res = [("name_1", "value_1"), ("name_2", "value_2")]
    expected_vals = ["value_1", "value_2"]
    db_engine = MagicMock()
    db_engine.execute(query).fetchall().return_value = query_res
    vals = func(db_engine)
    assert expected_vals == vals

总之，db_engine.execute(query).fetchall()必须返回列表，所以我可以迭代query_result，但它不会发生。尽管在attributequery_result中有正确的值return_value，但我无法对其进行迭代。

标签： pythonunit-testingmockingpython-unittestmagicmock

解决方案

您可以在此处找到如何模拟链式调用文档。这是单元测试解决方案：

func.py：

def func(db_engine):
    query = f"SELECT * FROM table"
    query_result = db_engine.execute(query).fetchall()
    extracted_val = []
    for res in query_result:
        extracted_val.append(res[1])
    return extracted_val

test_func.py：

import unittest
from func import func
from unittest.mock import MagicMock


class TestFunc(unittest.TestCase):
    def test_func(self):
        query_res = [("name_1", "value_1"), ("name_2", "value_2")]
        expected_vals = ["value_1", "value_2"]
        db_engine = MagicMock()
        execute = db_engine.execute.return_value
        execute.fetchall.return_value = query_res
        vals = func(db_engine)

        db_engine.execute.assert_called_with("SELECT * FROM table")
        execute.fetchall.assert_called_once()
        self.assertEqual(expected_vals, vals)


if __name__ == '__main__':
    unittest.main()

覆盖率 100% 的单元测试结果：

.
----------------------------------------------------------------------
Ran 1 test in 0.001s

OK
Name                                      Stmts   Miss  Cover   Missing
-----------------------------------------------------------------------
src/stackoverflow/61318070/func.py            7      0   100%
src/stackoverflow/61318070/test_func.py      16      0   100%
-----------------------------------------------------------------------
TOTAL                                        23      0   100%

蟒蛇版本：Python 3.7.5

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