Add Unit Tests for Empty and Single-Node Graphs in TopologicalSort

[Saipatnaik-23]

Description

This PR adds two basic unit tests to improve the test coverage of the existing TopologicalSort implementation in com.thealgorithms.sorts.TopologicalSort.java.

What's Included:

✅ testEmptyGraph(): Ensures that an empty graph returns an empty sorted list.

✅ testSingleNode(): Verifies correct output for a graph with a single node and no edges.

Checklist

• 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

let me know if improvements are needed. 😊

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.07%. Comparing base (ed4a724) to head (4447243).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6263   +/-   ##
=========================================
  Coverage     74.07%   74.07%           
  Complexity     5351     5351           
=========================================
  Files           677      677           
  Lines         18648    18648           
  Branches       3621     3621           
=========================================
  Hits          13813    13813           
  Misses         4276     4276           
  Partials        559      559           

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[Saipatnaik-23]

Hello maintainers! This PR is ready for review — all checks are passing. Please let me know if any changes are needed. Thank you! 😊

[Saipatnaik-23]

Hello @DenizAltunkapan Added new test cases for empty and single-node graphs in the existing src/main/java/com/thealgorithms/sorts/TopologicalSort.java . Please review. Thanks!

[Saipatnaik-23]

Hello @DenizAltunkapan , I’ve reverted my changes to the pom.xml file and added two test cases for Topological Sort. All checks have passed. Please have a look and review when you get a chance. Thank you looking forward to your feedback.

[siriak]

Looks good, thanks!