Description

Added Hypothesis property-based testing to the PowerPoint skill, covering four core modules with 18 property tests. A shared strategies module and CI/dev Hypothesis profiles provide the testing infrastructure. Property testing uncovered a numeric sort bug in discover_images, which was fixed in this PR.

Property-Based Tests

Eighteen property tests exercised invariants, round-trip behavior, boundary conditions, and idempotency across four production modules.

• Added test_fuzz_pptx_colors.py with six tests: resolve_color always-returns-dict, contains-rgb-or-theme, hex-idempotent; hex_brightness result 0–255; rgb_to_hex output format; and color round-trip preserving color type through shape fill.
• Added test_fuzz_pptx_tables.py with four tests: table round-trip preserving row count, column count, and cell text through add/extract; merge boundary raising IndexError for out-of-bounds spans.
• Added test_fuzz_build_deck.py with three tests: discover_slides output-sorted and only-matching-dirs invariants; get_slide_layout always-returns-layout for arbitrary names.
• Added test_fuzz_validate_slides.py with five tests: discover_images output-is-sorted and all-paths-match-pattern; max_severity ordering-monotonic, empty-returns-none, and result-in-valid-set.

Shared Test Infrastructure

• Added strategies.py with reusable Hypothesis strategies for hex colors, theme references, table elements, positions, issues, and severity results. The table_element composite strategy restricts text to XML-safe Unicode categories.
• Updated conftest.py with ci and dev Hypothesis profiles (200 vs 50 max_examples, derandomize in CI, suppressed too_slow health check), plus make_blank_presentation() and make_blank_slide() helper functions as plain functions for use inside @given-decorated tests.

Bug Fix

• Fixed discover_images in validate_slides.py to sort by numeric slide number instead of lexicographic filesystem order. Previous behavior sorted slide-10 before slide-2.

Configuration

• Added hypothesis>=6.100 dev dependency and hypothesis pytest marker to pyproject.toml.
• Configured [tool.coverage.run] source=["scripts"] and [tool.coverage.report] fail_under=85 with show_missing.
• Added **/.hypothesis/ to .gitignore for Hypothesis example database directories.

Related Issue(s)

Closes #1013

Type of Change

Select all that apply:

Code & Documentation:

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to change)
• Documentation update

Infrastructure & Configuration:

• GitHub Actions workflow
• Linting configuration (markdown, PowerShell, etc.)
• Security configuration
• DevContainer configuration
• Dependency update

AI Artifacts:

• Reviewed contribution with prompt-builder agent and addressed all feedback
• Copilot instructions (.github/instructions/*.instructions.md)
• Copilot prompt (.github/prompts/*.prompt.md)
• Copilot agent (.github/agents/*.agent.md)
• Copilot skill (.github/skills/*/SKILL.md)

Note for AI Artifact Contributors:

• Agents: Research, indexing/referencing other project (using standard VS Code GitHub Copilot/MCP tools), planning, and general implementation agents likely already exist. Review .github/agents/ before creating new ones.
• Skills: Must include both bash and PowerShell scripts. See Skills.
• Model Versions: Only contributions targeting the latest Anthropic and OpenAI models will be accepted. Older model versions (e.g., GPT-3.5, Claude 3) will be rejected.
• See Agents Not Accepted and Model Version Requirements.

Other:

• Script/automation (.ps1, .sh, .py)
• Other (please describe):

Sample Prompts (for AI Artifact Contributions)

Testing

• 587 tests passed after merging with origin/main (up from 549 on the base branch).
• 18 new Hypothesis property tests verified invariants, round-trip behavior, boundary conditions, and idempotency across pptx_colors, pptx_tables, build_deck, and validate_slides.
• Coverage measured at 90%, exceeding the 85% fail_under threshold.
• Ruff linting passed with no issues.

Checklist

Required Checks

• Documentation is updated (if applicable)
• Files follow existing naming conventions
• Changes are backwards compatible (if applicable)
• Tests added for new functionality (if applicable)

AI Artifact Contributions

• Used /prompt-analyze to review contribution
• Addressed all feedback from prompt-builder review
• Verified contribution follows common standards and type-specific requirements

Required Automated Checks

The following validation commands must pass before merging:

• Markdown linting: npm run lint:md
• Spell checking: npm run spell-check
• Frontmatter validation: npm run lint:frontmatter
• Skill structure validation: npm run validate:skills
• Link validation: npm run lint:md-links
• PowerShell analysis: npm run lint:ps
• Plugin freshness: npm run plugin:generate

Security Considerations

• This PR does not contain any sensitive or NDA information
• Any new dependencies have been reviewed for security issues
• Security-related scripts follow the principle of least privilege

Additional Notes

• The hypothesis package (6.151.9) is a well-established property-based testing library with no known security vulnerabilities. Its only transitive dependency is sortedcontainers.
• Hypothesis profiles are automatically selected based on the CI environment variable, with the ci profile using derandomized inputs and no persistent database.
• The discover_images bug fix addressed a numeric vs. lexicographic sort issue that would have caused incorrect slide ordering for decks with 10+ slides.