Unittest Mock objects do not freeze arguments they are called with

[slacknate]

BPO	33309
Nosy	@rbtcollins, @ezio-melotti, @voidspace, @slacknate, @tirkarthi
Files	mock_issue.py: Reproduces described issue, assertion error raised when it should not be.

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-09-24.15:38:28.520>
created_at = <Date 2018-04-18.15:53:04.431>
labels = ['3.7', 'invalid', 'type-bug', 'library']
title = 'Unittest Mock objects do not freeze arguments they are called with'
updated_at = <Date 2018-09-24.15:38:28.519>
user = 'https://github.com/slacknate'

bugs.python.org fields:

activity = <Date 2018-09-24.15:38:28.519>
actor = 'xtreak'
assignee = 'none'
closed = True
closed_date = <Date 2018-09-24.15:38:28.520>
closer = 'xtreak'
components = ['Library (Lib)']
creation = <Date 2018-04-18.15:53:04.431>
creator = 'slacknate'
dependencies = []
files = ['47539']
hgrepos = []
issue_num = 33309
keywords = []
message_count = 3.0
messages = ['315456', '319816', '326253']
nosy_count = 5.0
nosy_names = ['rbcollins', 'ezio.melotti', 'michael.foord', 'slacknate', 'xtreak']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33309'
versions = ['Python 3.7']

[slacknate]

It is possible to make a call with a Mock object, for example, where a dictionary is passed to the mock and later modified. If a call assertion is then made against the mock using the initial value/contents of the dictionary the assertion will fail.

[tirkarthi]

Thanks for the issue. I think this is documented here : https://docs.python.org/3/library/unittest.mock-examples.html#coping-with-mutable-arguments

Thanks

[tirkarthi]

Thanks for the details. As part of triaging I am closing this as not a bug since passing mutable arguments to a mock object and modifying it is a documented behavior at https://docs.python.org/3/library/unittest.mock-examples.html#coping-with-mutable-arguments . Feel free to reopen this if needed.

Thanks