Fix test reliability of truncating causes

[guperrot]

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Description

Last attempts were not enough: https://msmobilecenter.visualstudio.com/SDK/_build/results?buildId=375780&view=logs

To verify cause truncation we just need to test utility anyway.

Needed for #866

[coveralls]

Coverage remained the same at 100.0% when pulling 96d3017 on fix/test-reliability into e2bd17b on develop.