Add test case for JSON resource marshaling

[ShervilG]

Added more JSON Marshal Test cases for #55

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2b8c7fa) 97.72% compared to head (895a768) 92.86%.
Report is 10 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3079      +/-   ##
==========================================
- Coverage   97.72%   92.86%   -4.86%     
==========================================
  Files         153      170      +17     
  Lines       13390    11400    -1990     
==========================================
- Hits        13085    10587    -2498     
- Misses        215      723     +508     
  Partials       90       90              

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