Add tests Sudoku

[lorduke22]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.22%. Comparing base (1c978c5) to head (955df5a).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5722      +/-   ##
============================================
+ Coverage     62.98%   63.22%   +0.24%     
- Complexity     4049     4068      +19     
============================================
  Files           569      569              
  Lines         16056    16056              
  Branches       3086     3086              
============================================
+ Hits          10113    10152      +39     
+ Misses         5525     5489      -36     
+ Partials        418      415       -3     

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