Add matrix unit tests

[ekam313]

Description

Added Catch2 unit tests for matrix-related functions by converting the old manual matrix checks into automated assertions in coresdk/src/test/unit_tests/unit_test_matrix.cpp.

The new tests cover:

• identity_matrix
• matrix_inverse
• matrix_to_string
• scale_matrix
• rotation_matrix
• translation_matrix
• matrix_multiply
• combined rotation + translation matrix inverse check

This improves automated test coverage for matrix functionality and replaces manual output checking with repeatable u\nit tests.

Fixes # (issue)

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Tested on Windows using MSYS2 MinGW64.

Commands used:

cd projects/cmake
cmake --preset Windows
cmake --build build/

cd ../../bin
./skunit_tests.exe "*matrix*" --success
./skunit_tests.exe --order rand

Checklist

• Tested with sktest
• Tested with skunit_tests

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have requested a review from ... on the Pull Request

[kyriesk]

Peer Review

I tested the unit_test_matrix.cpp on my local machine using a WSL setup, and all tests passed without issues. The code follows SplashKit’s coding standards and behaves functional.

[222448082Ashen]

General Information

• Type of Change: New feature (Unit Testing)

Code Quality

• Repository: Correct. The PR is made to splashkit-core.
• Readability: High. The tests are well-organized by functionality and use a clear, property-based verification approach (e.g., verifying that a matrix multiplied by its inverse yields the identity matrix).
• Maintainability: High. The tests rely on standard SplashKit types and formatting functions, making them robust against internal implementation changes as long as the API and output format remain stable.

Functionality

• Correctness: The tests comprehensively cover the matrix_2d module:
  • Identity Property: Verifies identity_matrix() and that multiplying by identity is a no-op.
  • Inverse Operations: Correctly tests that inversion works for scaling, rotation, translation, and combinations thereof.
  • Edge Cases: Verifies that scale_matrix(1) and translation_matrix(0, 0) correctly return identity matrices.
  • Formatting: Explicitly tests the matrix_to_string output, which is crucial for debugging tools that rely on this format.
• Impact on Existing Functionality: No impact on library code.

Testing

• Test Coverage: This PR fills a significant gap in the unit test suite, as matrix operations are foundational to many other SplashKit modules (sprites, geometry, etc.).
• Test Results: Logic check: The string comparison for matrix_to_string aligns perfectly with the setw(8) and setprecision(3) implementation found in matrix_2d.cpp.

Documentation

• Documentation: The test code is clear and self-documenting.

Pull Request Details

• Checklist Completion: All relevant items reviewed.

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[222448082Ashen]

Recommendations & Observations

1. Floating Point Comparison: The PR uses matrix_to_string comparison for inverse operations:

   REQUIRE(matrix_to_string(matrix_multiply(matrix, inv_matrix)) == matrix_to_string(identity_matrix()));

   This is an effective way to handle small floating-point variances in Catch2, as matrix_to_string uses setprecision(3), which naturally masks negligible errors. It's a clever and readable alternative to manual epsilon checks for these specific tests.
2. Header Usage: The test includes #include "physics.h". While matrix_2d is used in physics, it's primarily defined in the geometry/graphics layers. Including matrix_2d.h or geometry.h directly might be slightly more precise, but physics.h works if it pulls in the necessary types.