Investigate Pester v6 changes

Even if our tests suite is still compatible and working with v6 since #658, there are many changes in v6 that might worth some investigations: https://github.com/pester/Pester/releases/tag/6.0.0
1) https://github.com/pester/Pester/releases/tag/6.0.0#new-should--assertions
2) https://github.com/pester/Pester/releases/tag/6.0.0#richer-failure-messages-and-output

If there is appetite and for contributors that know what they're doing and/or have access to a Windows machine to run tests locally without relying too much on CI, there is also this one that could be interesting:
3) https://github.com/pester/Pester/releases/tag/6.0.0#parallel-test-execution-experimental

Read the Pester v6 release notes linked in the issue, starting with new Should assertions and richer failure messages; the parallel execution section is optional and requires Windows access. Inspect the repository's existing test suite for compatibility, and consider the work complete when applicable v6 changes and any parallel-execution findings are documented or implemented.

Written by the indexing model from the issue text.