Write Comprehensive NUnit Test Cases

I need test cases for prepackrepository.cs to cover all code lines.

Requirements:
- Use NUnit framework
- Create both unit and integration tests
- Mock:
- Database connections
- API calls
- File system operations

Ideal Skills:
- Proficiency in C# and NUnit
- Experience with mocking frameworks
- Background in writing unit and integration tests

Please ensure that all code paths are tested and provide a report on test coverage.