How to pytest local variable like dict inside function?

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For example I have a function like below:

def func(val):
    dict = {}
    # some logic to fill in dict
    dict['a'] = val

Then how can I pytest the the contents of dict? Is it possible?

pytest python
1 Answers

You can actually replace the dict constructor, for the tested module, if you can change your code slightly. Suppose that your module name is my_module.py and you can make the following changes:

  1. Initialize the dictionary using dict() instead of {}
  2. Rename dict into my_dict (or any other name so it doesn't shadows the builtin dict())

my_module.py would look like so:

def func(val):
    my_dict = dict()  # instead of dict = {}
    # some logic to fill in dict
    my_dict['a'] = val

Then, in your test, override the dict constructor which creates new dictionaries and return your dictionary that you can assert later on:

from my_module import func


def test_func(mocker):
    my_replaced_dict = {}
    mocker.patch("my_module.dict", return_value=my_replaced_dict)
    func(20)
    assert my_replaced_dict['a'] == 20  # the assert works since func uses our variable
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