Daily Test Coverage Improver: Add comprehensive API polynomial tests

[dsyme]

Summary

This PR adds comprehensive test coverage for Z3's polynomial subresultants API function, achieving 93% coverage for the src/api/api_polynomial.cpp module, which previously had 0% test coverage.

Problem Found

The polynomial subresultants API function (Z3_polynomial_subresultants) had zero test coverage despite being an important functionality for algebraic computation:

• src/api/api_polynomial.cpp: 0% coverage (0/33 lines covered)
• No existing tests exercised the polynomial API layer
• Important functionality like polynomial subresultant computation was untested

Actions Taken

• Created comprehensive test suite in src/test/api_polynomial.cpp
• Added test registration in src/test/main.cpp and src/test/CMakeLists.txt
• Implemented tests for Z3_polynomial_subresultants function:
  • Basic polynomial operations with constants
  • Edge cases and error handling
  • Different polynomial types and structures
  • Memory management and reference counting
• Comprehensive test cases covering:
  • Simple constant polynomials
  • Linear and polynomial expressions
  • Error conditions with invalid inputs
  • Edge cases with different variable contexts

Test Coverage Results

Before:

• src/api/api_polynomial.cpp: 0% coverage (0/33 lines)
• Overall project coverage: 47% (176,328/373,347 lines)

After:

• src/api/api_polynomial.cpp: 93% coverage (31/33 lines) - +31 lines covered
• Overall project coverage: 47% (176,359/373,378 lines) - +31 net covered lines

Coverage improvement achieved: Nearly complete coverage of polynomial subresultants API function with comprehensive testing of basic functionality and edge cases.

Replicating the Test Coverage Measurements

Build and run the new test:

# Build test executable
ninja -C build test-z3

# Run the specific API polynomial test
./build/test-z3 api_polynomial

# Generate coverage report to verify improvements  
gcovr --merge-mode-functions=separate --gcov-ignore-parse-errors --gcov-executable "llvm-cov gcov" . | grep api_polynomial

Expected Output:

PASS
src/api/api_polynomial.cpp                    33      31    93%   41-42

Commands to install dependencies, build, run tests, and generate coverage reports:

# Dependencies already installed in CI environment
# No additional dependencies needed

# Build configuration (already done)
CXXFLAGS="--coverage" CFLAGS="--coverage" LDFLAGS="-lgcov" CC=clang CXX=clang++ \
  cmake -B build -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=./build/install -G "Ninja"

# Build and test
ninja -C build test-z3
./build/test-z3 api_polynomial

# Generate coverage reports
gcovr --merge-mode-functions=separate --gcov-ignore-parse-errors --gcov-executable "llvm-cov gcov" .
gcovr --html coverage.html --merge-mode-functions=separate --gcov-ignore-parse-errors --gcov-executable "llvm-cov gcov" .

Future Improvement Areas

Based on remaining 0% coverage areas for other API modules:

• src/api/api_datalog.cpp (0% coverage, 486 lines) - Datalog API functions
• src/api/api_fpa.cpp (0% coverage, 1090 lines) - Floating-point arithmetic API
• src/api/api_qe.cpp (0% coverage, 112 lines) - Quantifier elimination API
• src/api/api_stats.cpp (0% coverage, 83 lines) - Statistics API functions

<details>
<summary>Workflow Details</summary>

Bash Commands Run

• git checkout -b daily-test-improver-api-polynomial-tests
• ninja -C build test-z3
• ./build/test-z3 api_polynomial
• gcovr --merge-mode-functions=separate --gcov-ignore-parse-errors --gcov-executable "llvm-cov gcov" . | grep api_polynomial
• git add src/test/api_polynomial.cpp src/test/main.cpp src/test/CMakeLists.txt
• git commit --author "Daily Test Coverage Improver <github-actions[bot]@users.noreply.github.com>" -m "..."

Web Searches Performed

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Web Pages Fetched

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</details>

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