Retry test_psu.py::TestPsuApi::test_power if power not within tolerance

[smagarwal-arista]

Description of PR

Summary:
If test_psu.py::TestPsuApi::test_power fails on abs(power - (voltage*current)) < power*0.1 then retry the test. The test is repeated for a maximum of three times until it passes, else it is failed. This change is introduced to account for the stringent tolerance level of 10% and the errors that might be caused due to time differences in reading each of the parameters (current, voltage and power).

Fixes # (issue)
Addresses issue: https://github.com/aristanetworks/sonic-qual.msft/issues/209

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 202012
• 202205
• 202305
• 202311
• 202405

Approach

What is the motivation for this PR?

Improve the test to account for stringent tolerance level and asymmetric reading of parameters for power calculation.

How did you do it?

If the test fails for the condition abs(power - (voltage*current)) < power*0.1, the test will collect fresh parameters (voltage, current and power) from the PSU telemetry and recheck the condition. It is limited to a maximum of 3 attempts.

How did you verify/test it?

Tested internally by varying the tolerance level and verifying the number of api calls.

Any platform specific information?

N/A

Supported testbed topology if it's a new test case?

N/A

Documentation

N/A

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Failed
- hook id: trailing-whitespace
- exit code: 1
- files were modified by this hook

Fixing tests/platform_tests/api/test_psu.py

fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/platform_tests/api/test_psu.py:210:29: E231 missing whitespace after ','
tests/platform_tests/api/test_psu.py:238:37: E128 continuation line under-indented for visual indent
tests/platform_tests/api/test_psu.py:252:33: E128 continuation line under-indented for visual indent
tests/platform_tests/api/test_psu.py:256:121: E501 line too long (122 > 120 characters)
tests/platform_tests/api/test_psu.py:260:37: E128 continuation line under-indented for visual indent
...
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[smagarwal-arista]

/azpw run Azure.sonic-mgmt

[mssonicbld]

/AzurePipelines run Azure.sonic-mgmt

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[vvolam]

How does the self.assert_expectations() evaluate the 3 test run values? What happens for different combinations of the expected values? For example:

Test1: True
Test2: False
Test3: True

In this combination, does the test raise assert or passes?