Added tests for FactorialRecursion

[marysiuniq]

Added tests for FactorialRecursion.

• 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 37.24%. Comparing base (05626f7) to head (86bd720).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5109      +/-   ##
============================================
+ Coverage     37.20%   37.24%   +0.04%     
- Complexity     2338     2343       +5     
============================================
  Files           517      517              
  Lines         15637    15630       -7     
  Branches       2979     2975       -4     
============================================
+ Hits           5817     5822       +5     
+ Misses         9532     9521      -11     
+ Partials        288      287       -1     

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[vil02]

Thanks!

If you would be looking for ideas for further PRs you can consider merging tests of Factorial.java and FactorialRecursion.java into a single file similarly as you did in your previous PR #5107.