python - How to change return value of mocked obj? -

i have class with

import pandas pd  class foo(object):    def __init__(self):       self.info = pd.dataframe()     def getdata(self):       self.__readcsv()     def __readcsv(self):       self.info = pd.read_csv(self.filename) 

i have unit test class with

class test(unittest.testcase):    def test(self):       mock = patch('foo.pandas.read_csv')       foo().getdata()        ... 

how can change pd.read_csv(self.filename) return value dataframe({'column1': series([1., 2., 3.]),'column2': series([4., 5., 6.])}) test whether self.info assigned, assertequal?

are using python 3 ? python 3 has built in mock library, python 2.x need use third party mock library (http://www.voidspace.org.uk/python/mock/index.html).

to mock pd.read_csv can use following

# python 3.x unittest.mock import patch  # python 2.x # mock import patch import pandas pd  class test(unittest.testcase):     @patch('foo.pd.read_csv')     def test(self, mock_read_csv):         mock_read_csv.return_value = pd.dataframe({'column1': series([1., 2., 3.]),'column2': series([4., 5., 6.])})         assert foo().getdata()