Extend all Posix-Wrapper unit tests with direct posix calls

## Brief feature description

The current posix wrapper are tested in a way that only the wrapper itself is used and tested with itself. If possible, we should call the posix calls directly in one part of a tests and verify that the posixWrapper behaves as intended when it works on the structure.

## Detailed information

Locate the Posix-wrapper unit tests and identify how they currently exercise the wrapper exclusively. Read the relevant POSIX calls and test setup first, then extend each test area with direct POSIX calls and verify that the wrapper produces the expected results when operating on the same structure.

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