Improve Aho-Corasick multiple occurrence test

[SameerVaranasi]

• 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 algorithms include a corresponding test class that validates their functionality.
• 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 80.61%. Comparing base (6ec6339) to head (d15bce4).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #7590   +/-   ##
=========================================
  Coverage     80.61%   80.61%           
  Complexity     7497     7497           
=========================================
  Files           816      816           
  Lines         24097    24097           
  Branches       4741     4741           
=========================================
  Hits          19427    19427           
  Misses         3907     3907           
  Partials        763      763           

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