Added unit tests for the go backend

[ssannkkallpp]

Adds a comprehensive unit test suite for the Go backend. Tests cover the handlers, services, and validation layers using temporary in-memory git repositories.

Running the Tests

From the go-backend/ directory:

# Run all tests
go test ./tests/...

# Run with verbose output (shows logs and per-test results)
go test ./tests/... -v

Test Structure

go-backend/tests/
├── main_test.go        # TestMain entry point — initializes the logger
├── handlers_test.go    # HTTP-level tests for API endpoints via httptest
├── services_test.go    # Unit tests for git and metadata service functions
├── validation_test.go  # Unit tests for path/repo validation utilities
└── helpers/
    └── helpers.go      # SetupTestRepo — creates a temporary git repo with a 
                        # gittuf policy commit for cross-suite use

[patzielinski]

I suggest using gittuf's testing helpers to create a repository here, e.g. copy/use https://github.com/gittuf/gittuf/blob/main/internal/policy/helpers_test.go.

Verification of gittuf repos is likely on the roadmap for the visualizer so having the test methods ready to plug in to that would be good.

[patzielinski]

I suggest bundling the tests into a parent test with child t.Runs, e.g. TestCloneAndFetchRepo with t.Run for each individual case. See https://github.com/gittuf/gittuf/blob/main/internal/policy/policy_test.go#L25 for an example.

[patzielinski]

Is this a listing/description file that you intended to add?