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39b74a23 - fix(test): Remedy macOS-only test failure not triggered by CI (#2957)

fix(test): Remedy macOS-only test failure not triggered by CI (#2957) **Summary** A crude and OS-specific mechanism was used to detect when a path represented a temp-file. Change that to be robust across operating systems and localized configurations. The specific problem was for DOC files but this PR fixes it for PPT too which was prone to the same problem.