在Mock上迭代返回的值

Question

我正在尝试Mock返回列表的方法。在设置了return_value之后，它仍然返回一个Mock对象，而不是列表，所以我不能迭代该对象。

我想测试的功能示例：

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list，所以我可以对query_result进行迭代，但这并没有发生。虽然query_result在矩阵return_value中有一个正确的值，但我不能迭代它

Answer 1

您可以在这里找到如何模拟链式调用文档。以下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()

100%覆盖率的单元测试结果：

.
----------------------------------------------------------------------
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%

Python版本：Python 3.7.5