33295: Eliminate AspectMock from FileStorageTest

[karyna-tsymbal-atwix]

Eliminated AspectMock usage from dev/tests/unit/Magento/FunctionalTestFramework/DataGenerator/Handlers/SecretStorage/FileStorageTest.php

note: in this case, main complexity is in a private functions calls rather than static

Fixed Issues (if relevant)

1. Fixes magento/magento2#33295: [MFTF] Eliminate AspectMock from FileStorageTest (Complex!)

Contribution checklist

• [ ] Pull request has a meaningful description of its purpose
• [ ] All commits are accompanied by meaningful commit messages
• [ ] All new or changed code is covered with unit/verification tests (if applicable)
• [ ] All automated tests passed successfully (all builds on Travis CI are green)
• [ ] Changes to Framework doesn't have backward incompatible changes for tests or have related Pull Request with fixes to tests

[andrewbess]

Hello @karyna-tsymbal-atwix Thank you for your PR. It looks well to me.

[jilu1]

@magento import pull request to https://github.com/magento-commerce/magento2-functional-testing-framework

[magento-engcom-team]

@jilu1 the pull request successfully imported.

[bohdan-harniuk]

Hello, @jilu1

This task was finished without creating new singletons, so it is not a blocker.

Thanks, Bohdan