python - 我怎样才能模拟 sqlite3.Cursor

Question

我一直在努力想弄清楚如何模拟 sqlite3.Cursor 类，特别是 fetchall 方法。

考虑以下代码示例

import sqlite3

from mock import Mock, patch
from nose.tools import assert_false


class Foo:
    def check_name(name):
        conn = sqlite3.connect('temp.db')
        c = conn.cursor()
        c.execute('SELECT * FROM foo where name = ?', name)
        if len(c.fetchall()) > 0:
            return True
        return False


@patch('sqlite3.Cursor.fetchall', Mock(return_value=['John', 'Bob']))
def test_foo():
    foo = Foo()
    assert_false(foo.check_name('Cane'))

运行 nosetests 导致没有有趣的错误

E
======================================================================
ERROR: temp.test_foo
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/koddsson/.virtualenvs/temp/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/home/koddsson/.virtualenvs/temp/lib/python2.7/site-packages/mock.py", line 1214, in patched
    patching.__exit__(*exc_info)
  File "/home/koddsson/.virtualenvs/temp/lib/python2.7/site-packages/mock.py", line 1379, in __exit__
    setattr(self.target, self.attribute, self.temp_original)
TypeError: can't set attributes of built-in/extension type 'sqlite3.Cursor'

----------------------------------------------------------------------
Ran 1 test in 0.002s

FAILED (errors=1)

我不应该模拟 fetchall 方法还是我做错了什么？

Answer 1

我会采用修补模块中导入的 sqlite3 的方法，然后从那里开始工作。

假设您的模块名为 what.py。

我会修补 what.sqlite3 然后模拟 .connect().cursor().fetchall 的返回值。

这是一个更完整的例子:

from mock import patch
from nose.tools import assert_true, assert_false

from what import Foo

def test_existing_name():
    with patch('what.sqlite3') as mocksql:
        mocksql.connect().cursor().fetchall.return_value = ['John', 'Bob']
        foo = Foo()
        assert_true(foo.check_name('John'))