单元测试模拟函数输出

Question

我刚刚在 Python2.7 中找到了一个模拟库，想对我的函数进行单元测试。无论我读什么教程，它总是关于类。我无法使用模拟功能。该项目的结构方式是，我有一些帮助功能可用于从数据库中收集和解析数据的一个功能。我想模拟数据库功能和查询功能。对于简单的情况，它看起来像这样：

import unittest
import mock

def queryFnc(arg=0):
    # imitate returned result from a query
    if arg == 0:
        return "queryFunc 0"
    else: return "queryFunc 1"

def parsingFunc():
    # function will parse result returned from a query
    myString = queryFnc().upper()
    return myString

class Test(unittest.TestCase):
    def test_queryFunc0(self):
        self.assertEquals("queryFunc 0", queryFnc(arg=0))
    def test_queryFunc1(self):
        self.assertEquals("queryFunc 1", queryFnc(arg=1))
    @mock.patch('.queryFnc', return_value='queryMock')
    def test_queryMock(self, queryFnc):
        self.assertEquals('queryMock', queryFnc())

    def test_parsingFunc(self):
        self.assertEquals('QUERYFUNC 0', parsingFunc())
    @mock.patch('.queryFnc', return_value='queryMock')
    def test_parsingFuncMock(self):
        self.assertEquals('QUERYMOCK', parsingFunc())

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

我预计 @mock.patch 会替换调用中的函数，但我可以让它工作。我有这个错误：

======================================================================
ERROR: test_queryMock (__main__.Test)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "\site-packages\mock\mock.py", line 1297, in patched
    arg = patching.__enter__()
  File "\site-packages\mock\mock.py", line 1353, in __enter__
    self.target = self.getter()
  File "\site-packages\mock\mock.py", line 1523, in <lambda>
    getter = lambda: _importer(target)
  File "\site-packages\mock\mock.py", line 1206, in _importer
    thing = __import__(import_path)
ValueError: Empty module name

有没有办法在另一个函数中使用不同的函数结果？我不得不使用 Python2.7

Answer 1

The basic principle is that you patch where an object is looked up。您可以使用 mock 赋值、with 比赛管理器和 @mock.patch 装饰器。我附上了几个案例的代码，其中包含 print 语句，向您显示函数何时查找原始对象以及在哪里查找模拟对象。

# CASE 1 taking query as mock inside test_ function
def test_queryMock1(self):
    queryFnc = mock.Mock(return_value = 'case1')
    print("Case 1 inside test_ after mock assignemnt", queryFnc(), queryFnc(1))
    self.assertEquals('case1', queryFnc(1))
print("Case1 after outside", queryFnc(), queryFnc(1))

# CASE 2 contest management with
def test_queryMock2(self):
    print("Case 2 inside test", queryFnc(), queryFnc(1))
    with mock.patch('__main__.queryFnc', return_value='case2'):
        print("Case 2 after with", queryFnc(), queryFnc(1))
        self.assertEquals('case2', queryFnc())
print("Case 2 outside", queryFnc(), queryFnc(1))  

# CASE 3 patching
@mock.patch('__main__.queryFnc', return_value='case3')
def test_queryMock3(self, *args):
    self.assertEquals('case3',queryFnc())

# CASE 4 using contest management for nested function
def test_InsideWith(self):
    print("Case 4 inside test_", queryFnc(), queryFnc(1)) 
    #with mock.patch('__main__.queryFnc', side_effect=mockText) as mock_function_obj:
    with mock.patch('__main__.queryFnc', return_value='case4'):
        print("Case 4 inside with", queryFnc(), queryFnc(1))
        self.assertEquals('CASE4', parsingFunc())
print("Case 4 outside", queryFnc(), queryFnc(1))

# CASE 5 using patch decorator
@mock.patch('__main__.queryFnc', return_value='case5')
def test_Patch(self, *args):
    print("Case 5 inside test_ after patch", queryFnc(), queryFnc(1))
    self.assertEquals('CASE5', parsingFunc())
    print("Case 5 inside test_, assert", queryFnc(), queryFnc(1))
print("Case 5 outside", queryFnc(), queryFnc(1))

请注意，在补丁中，模块被指定为 __main__ 您想要修补的地方。如果您尝试使用模块名称，您可以看到它如何改变补丁行为。

单元测试模拟函数输出

unittest mock function output

mocking

python-unittest

python-mock