Unit test for appgroup prepaid balance

[divya-intelli]

Fixes #450

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.27%. Comparing base (fb6604a) to head (e529593).
⚠️ Report is 1 commits behind head on appgroup-mint-3.x.

Additional details and impacted files

@@                   Coverage Diff                   @@
##             appgroup-mint-3.x     #451      +/-   ##
=======================================================
+ Coverage                86.12%   86.27%   +0.14%     
  Complexity                1800     1800              
=======================================================
  Files                      360      360              
  Lines                     4715     4715              
=======================================================
+ Hits                      4061     4068       +7     
+ Misses                     654      647       -7     

Flag	Coverage Δ
unittests	86.27% <ø> (+0.14%)	⬆️

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see 1 file with indirect coverage changes

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[shishir-intelli]

LGTM