Fix flaky test

[martincostello]

Attempt to fix flaky test where SystemClock.Sleep() doesn't throw when expected.

[Copilot]

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.36%. Comparing base (dc4010a) to head (5a12054).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2457      +/-   ##
==========================================
- Coverage   85.39%   85.36%   -0.03%     
==========================================
  Files         312      312              
  Lines        7464     7464              
  Branches     1121     1121              
==========================================
- Hits         6374     6372       -2     
- Misses        905      907       +2     
  Partials      185      185              

Flag	Coverage Δ
linux	85.36% <ø> (ø)
macos	85.36% <ø> (ø)
windows	85.33% <ø> (-0.03%)	⬇️

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[martincostello]

Latest commit passed 5 times in a row, so assuming it's fixed... 🤞