{Core} Fix: test_credscache_good_error_on_file_corruption fails when run in parallel with other tests

[jiasli]

Symptom

Fix: test_credscache_good_error_on_file_corruption fails when run in parallel with other tests

CI failure:

https://dev.azure.com/azure-sdk/playground/_build/results?buildId=806624&view=logs&j=abe8eae2-a613-5a65-3eeb-3e8a13573181&t=ff49c02d-6a40-524c-c9b1-98f6bb13c7f4&l=2248

__________ TestProfile.test_credscache_good_error_on_file_corruption ___________
[gw0] linux -- Python 3.8.8 /home/vsts/work/1/s/env/bin/python
self = <azure.cli.core.tests.test_profile.TestProfile testMethod=test_credscache_good_error_on_file_corruption>
get_file_json_mock = <function get_file_json at 0x7f723502fee0>

    @mock.patch('azure.cli.core._profile.get_file_json', autospec=True)
    def test_credscache_good_error_on_file_corruption(self, get_file_json_mock):
        get_file_json_mock.side_effect = ValueError('a bad error for you')
        cli = DummyCli()
    
        # action
        creds_cache = CredsCache(cli, async_persist=False)
    
        # assert
        with self.assertRaises(CLIError) as context:
>           creds_cache.load_adal_token_cache()
E           AssertionError: CLIError not raised

src/azure-cli-core/azure/cli/core/tests/test_profile.py:1799: AssertionError

Root cause

The test test_credscache_good_error_on_file_corruption assumes ~/.azure/accessTokens.json exists when it is run. If there is no ~/.azure/accessTokens.json,

azure-cli/src/azure-cli-core/azure/cli/core/_profile.py

Line 109 in 50ccb24

if os.path.isfile(file_path):

evaluates to False, thus bypassing the code under test, causing failure.

This can also be repoed by deleting ~/.azure/accessTokens.json and only running test_credscache_good_error_on_file_corruption:

pytest src/azure-cli-core/azure/cli/core/tests/test_profile.py::TestProfile::test_credscache_good_error_on_file_corruption -o log_cli_level=DEBUG

⚠ In parallel testing, the existence of ~/.azure/accessTokens.json is not guaranteed, so the failure.

Change

Also patch os.path.isfile to make the test isolated from the underlying file system.

[yonzhan]

Core