tests: add tests to go/mathutil

[Maniktherana]

Description

Improves code coverage from 69% to 95.2% 100% for go/mathutil

Related Issue(s)

#14931

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c1f9c80) 47.26% compared to head (5110db0) 47.28%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14969      +/-   ##
==========================================
+ Coverage   47.26%   47.28%   +0.01%     
==========================================
  Files        1138     1138              
  Lines      238842   238842              
==========================================
+ Hits       112880   112927      +47     
+ Misses     117368   117323      -45     
+ Partials     8594     8592       -2     

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[frouioui]

LGTM, thank you!

[mattlord]

Thanks, @Maniktherana ! We can see that the coverage went from 61.43% on main to 100% on the PR branch:

• https://app.codecov.io/gh/vitessio/vitess/tree/main/go%2Fmathutil
• https://app.codecov.io/gh/vitessio/vitess/pull/14969/tree/go/mathutil