Mock a global variable in python

Question

I have a function in main module which takes in two values and performs opertaions on them.This uses a global variable which is created before calling this function

def calc(keys,values):
    if globalvar == "calc":
        return sum(keys)
    else:
        return sum(values)

Now in unittesting

class Testcalc(TestCase):
@mock.patch('module.globalvar ', "calc")
def test_unit(self,calc):
    keys=[1,2,3]
    values=[4,5,6]
    sum=module.calc(keys,values)
    """
    check asserts
    """

I am getting an type error with invalid arguments.

TypeError('test_unit() takes exactly 2 arguments (1 given)',)

Could anyone show me the correct way of mocking the global variable

Update: This worked for me not sure why

class Testcalc(TestCase):
@mock.patch('module.globalvar')
def test_unit(self,var):
    keys=[1,2,3]
    values=[4,5,6]
    var="calc"
    sum=module.calc(keys,values)
    """
    check asserts
    """

Thank you everyone

TypeError('test_unit() takes exactly 2 arguments (1 given)',) — Ram
– Ram, Commented Jul 27, 2018 at 15:44
Please include the line that calls test_unit(), i.e. where you use it. — GetHacked
– GetHacked, Commented Jul 27, 2018 at 16:05
I don’t think your error is related to the way you’re mocking the global. But without a minimal reproducible example it’s hard to be sure. What you’ve posted here has an IndentationError, and a slightly variation on the same indentation problem could cause an error much like the one you’re seeing, but I doubt that’s your problem. So show us code that actually reproduces your problem instead of a different one. — abarnert
– abarnert, Commented Jul 27, 2018 at 16:13

Gang · Accepted Answer · 2018-07-29 15:14:29Z

9

A module.globalvar = 'anything' should be enough, no need to mock.patch

def test_calc2(self):
    keys = [1, 2, 3]
    values = [4, 5, 6]

    module.globalvar = "calc"
    sum = module.calc(keys, values)
    self.assertEqual(module.globalvar, 'calc')
    self.assertEqual(sum, 6)

    module.globalvar = 'other'
    sum = module.calc(keys, values)
    self.assertEqual(sum, 15)

This works using PropertyMock

@mock.patch('module.globalvar', new_callable=mock.PropertyMock)
def test_calc3(self, mocked_globalvar):

This is syntax right, but will fail the test, since the globalvar has to be set by PropertyMock

@mock.patch('module.globalvar')
def test_unit(self, mock_globalvar):

edited Jul 29, 2018 at 15:14

answered Jul 27, 2018 at 23:53

Gang

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2 Comments

Ram Over a year ago

Thank u for replying @Gang, So can I use module.globalvar = 'anything' in the test_unit function as a paramter and it would work instead of patch?

def test_unit(self,var):     keys=[1,2,3]     values=[4,5,6]     module.globalvar = 'calc'     sum=module.calc(keys,values)     """     check

Gang Over a year ago

@Ram, sorry the module.globalvar is right, I included in the update, the @mock.patch part is wrong, it only works with mock.PropertyMock for globalvars, class attributes etc

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