test(af_colours): Add unit tests for af_colour functions

[wfahim]

Description

Summary

Added unit tests for the functions of af_colours.py

Related Issues

• Relates to Integrate the py_af_colours package #58

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes, no api changes)
• ⚡ Performance improvement
• 🧪 Test addition or improvement
• 🔨 Build/CI changes
• 🎨 Style/formatting changes

Changes Made

Testing

Test Coverage

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• No tests needed (explain why below)

Testing Details

Test Cases:

1. Test that requesting N colours from the categorical palette returns exactly N colours.
2. Test that requesting 2 colours from the categorical palette returns the same result as the duo palette (for both HEX and RGB formats).
3. Test that invalid inputs to af_colours correctly raise errors (invalid palette, invalid colour format, too few or too many colours).

Manual Testing Results:

Screenshots/Videos

Before

After

Breaking Changes

• No breaking changes
• Breaking changes (describe below)

Breaking Change Details:

Documentation

• Documentation updated
• README updated
• No documentation changes needed

Documentation Changes:

Dependencies

• No new dependencies
• New dependencies added (list below)
• Dependencies updated (list below)
• Dependencies removed (list below)

Dependency Changes:

Checklist

Code Quality

• Code follows the project's style guidelines
• Self-review of code completed
• Code is properly commented
• No unnecessary console.log/print statements
• No commented-out code (unless intentionally documented)

Testing & Quality Assurance

• Tests pass locally
• Tests added for new functionality
• Edge cases considered and tested
• Error handling implemented where appropriate

[nickhenden]

All works fine now, thanks Fahim. Merge when you're ready