test: Mock only service call in AHS device initialization

[yitchen-tim]

Description of changes:
Add noise model to mock aws device in unit test. This is an update for introducing BDK PR amazon-braket/amazon-braket-sdk-python#850

Testing done:
tox

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Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

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  Files            7         7           
  Lines         1185      1185           
  Branches       286       286           
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[speller26]

Why not include this in #850? The change doesn't make sense on its own.

[yitchen-tim]

@speller26 I didn't see a way for a PR to make changes in two different repository? Is there a better way than having two separate PRs?

[speller26]

Oops, thought this one was also in the SDK; in that case we'll just hold off until that PR is finalized. In the meantime, the prefix of the PR should be test: rather than fix:

[speller26]

The fact that we need to add the field here before we merge the SDK change indicates a problem with how our mocks are set up; we shouldn't have to add in a yet-to-be-introduced property here

[yitchen-tim]

yes, it's related to this mock. It should mock the individual attributes, instead of filling in what's necessary to a Mock.

[speller26]

Instead of adding a _noise_model attribute to the mock device for the test case, try replacing

amazon-braket-pennylane-plugin-python/test/unit_tests/test_ahs_device.py

Lines 236 to 237 in 8c6fd32

	m.setattr(AwsDevice, "__init__", lambda self, *args, **kwargs: None)
	m.setattr(AwsDevice, "aws_session", MockAwsSession)

with

m.setattr(AwsDevice, "_get_session_and_initialize", lambda self, *args, **kwargs: MockAwsSession) 

Instead of mocking out the entirety of __init__, and all the useful attributes that come with it, this will only mock out the service call, which should be much more robust.

[yitchen-tim]

Great, this solution is working! I also tested locally that amazon-braket/amazon-braket-sdk-python#850 will pass with this fix.