Provide assertion functions in unittest.mock

[OddBloke]

BPO	30949
Nosy	@OddBloke, @berkerpeksag, @pppery
Superseder	bpo-24651: Mock.assert* API is in user namespace

^{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 2017-10-26.08:37:33.151>
created_at = <Date 2017-07-17.14:36:43.006>
labels = ['3.7', 'type-feature', 'library']
title = 'Provide assertion functions in unittest.mock'
updated_at = <Date 2017-10-26.08:37:33.148>
user = 'https://github.com/OddBloke'

bugs.python.org fields:

activity = <Date 2017-10-26.08:37:33.148>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2017-10-26.08:37:33.151>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2017-07-17.14:36:43.006>
creator = 'odd_bloke'
dependencies = []
files = []
hgrepos = []
issue_num = 30949
keywords = []
message_count = 3.0
messages = ['298533', '298553', '305036']
nosy_count = 4.0
nosy_names = ['odd_bloke', 'berker.peksag', 'ppperry', 'tribaal']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '24651'
type = 'enhancement'
url = 'https://bugs.python.org/issue30949'
versions = ['Python 3.7']

[OddBloke]

The convenience assertion methods on mock objects can be easily mistyped and if they are mistyped, they will silently pass. This can be quite user-hostile. Consider the following:

>> example = Mock()
>> example.assert_called_once()
>> example.assert_caled_once_with(...)

This will not raise any exceptions, though the first feels natural and the latter is misspelt. To avoid using the methods, one can type:

>> example = Mock()
>> assert example.call_count == 1
>> assert example.call_args_list == [call(...)]

but the meaning of that latter statement is particularly non-obvious. Instead, it would be great if I could import the assertions from mock as functions, and call them with mock as the first argument:

>> from unittest.mock import assert_called_once # This will be an ImportError
>> example = Mock()
>> assert_caled_once_with(example, ...) # A NameError
>> assert_called_once_with(example, ...) # Great success!

[pppery]

You can already do this, although it it somewhat of a hack:

>> assert_called_once=Mock.assert_called_once # This will be an AttributeError
>> assert_called_once_with=Mock.assert_called_once_with
>> example = Mock()
>> assert_caled_once_with(example, ...) # A NameError
>> assert_called_once_with(example, ...) # Great success!

[berkerpeksag]

Thank you for the report. This is a duplicate of bpo-24651.