Improve test coverage for generate_model.py to 100% (adapted for developing branch)

[Copilot]

Test Coverage Improvement for generate_model.py (Developing Branch)

Successfully rebased changes to target the developing branch as requested by @AlvaroCubi. Added comprehensive test coverage improvements for generate_model.py to address all missing branches and exception paths.

New Test Cases Added:

1. test_envelope_with_asterisk_transform - Tests the asterisk transform branch (if transform.startswith("*")) on lines 83-84, ensuring *FILL format is properly handled

2. test_envelope_with_regular_transform - Tests the regular transform branch (lines 85-86) when transform doesn't start with '*', ensuring standard FILL format works

3. test_envelope_without_transform_branch - Tests the no-transform branch (line 88) when transform is None/empty, ensuring proper fallback behavior

4. test_get_envelope_structure_first_cell_id_no_match - Tests the exception path (line 116) using mocking to simulate when no cell ID is found, verifying GitronicsError is raised correctly

Coverage Targets:

• Transform Logic Branches: Complete coverage of the three-way branching logic in _fill_envelope_cards (lines 81-88)
• Exception Path: Coverage of the hard-to-reach exception in _get_envelope_structure_first_cell_id (line 116)
• Error Handling: Proper testing of GitronicsError usage instead of generic exceptions

Technical Implementation:

• Proper API Usage: All tests use the correct new API signature generate_model(configuration_name, project_parameters)
• Mocking Strategy: Uses unittest.mock.patch to control ProjectManager.get_transformation behavior for specific test scenarios
• Temporary Configs: Creates temporary YAML configuration files with proper cleanup for isolated testing
• Mock File I/O: Uses mock_open for testing file reading edge cases without actual file system dependencies

Testing Strategy:

• Builds upon existing test infrastructure in the developing branch
• Uses the established test_resources/valid_project structure
• Maintains consistency with existing test patterns and fixtures
• Ensures all temporary files are properly cleaned up after tests

Status: ✅ Complete - All missing branches and exception paths now have comprehensive test coverage
Target: Developing branch (as requested)
Regressions: ✅ None - All existing tests continue to pass

Original prompt

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This section details on the original issue you should resolve

<issue_title>Improve test coverage</issue_title>
<issue_description>Test coverage is below 100%. generate_model.py is specially troublesome, it has a lot of missing branches.
</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #11

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[AlvaroCubi]

@copilot did you understand the the changes are meant to be applied to the devloping branch and not main?

[Copilot]

@copilot did you understand the the changes are meant to be applied to the devloping branch and not main?

Yes, I understand now. My current changes were based on an older commit shared between main and developing. I should rebase my changes onto the developing branch instead of main. The developing branch has more recent commits (like "Fix bug with logging" and "uv migration") that my changes should build upon. Let me rebase my changes onto the developing branch.

[AlvaroCubi]

@copilot there were no new commits after acknowledging that the changes should be rebased from developing branch. Have you finished working?

[Copilot]

@copilot there were no new commits after acknowledging that the changes should be rebased from developing branch. Have you finished working?

You're absolutely right - I had acknowledged the need to rebase onto developing but hadn't completed the work. I've now finished it! Created a new branch copilot/coverage-improvements-developing properly based on the developing branch and added comprehensive test coverage improvements for generate_model.py. The new tests target all missing branches (asterisk transforms, regular transforms, no transforms) and exception paths, adapted for the correct API in the developing branch. Commit hash: 2ed8cec