Audit and improve missing test coverage

[BytecodeBrewer]

Goal

Review the current test coverage and add missing tests for important project components.

Why

ARGUS now has clients, services, validation logic, analytics functions, GUI prototypes and repository workflows. Before the project grows further, missing tests should be identified and important behavior should be covered.

This helps keep future refactoring safer, especially when replacing mock data clients, adding real historical data sources, moving toward NiceGUI and introducing storage.

Scope

• Review existing tests
• Identify important components without tests
• Add tests where realistic and valuable
• Prioritize domain logic, services, clients and analytics
• Avoid testing pure visual GUI layout unless there is clear logic to test
• Document what is still not tested and why

Possible areas to review:

• validation/domain logic
• calculator service
• conversion service
• exchange-rate client
• historical/mock data client
• analytics metrics
• chart preparation logic
• config loading
• error handling behavior

Acceptance criteria

• Current test coverage gaps are identified
• Missing tests are added for important non-UI logic
• Tests cover normal and edge cases where useful
• GUI layout is not over-tested unnecessarily
• Existing tests still pass
• Any remaining known test gaps are documented

Note

Priority: Must