Add test analytics

[martincostello]

Use Codecov's test analytics feature.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.72%. Comparing base (80276e3) to head (e075ac6).

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3376   +/-   ##
=======================================
  Coverage   84.72%   84.72%           
=======================================
  Files          84       84           
  Lines        3280     3280           
  Branches      572      572           
=======================================
  Hits         2779     2779           
  Misses        501      501           

Flag	Coverage Δ
Linux	65.03% <ø> (-19.70%)	⬇️
Windows	83.47% <ø> (ø)
macOS	83.47% <ø> (ø)

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