Snap CommandRunner Migration (Issue #20 Part 2)

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Summary

Migrate Snap package manager from direct exec.Command calls to unified CommandRunner interface for consistent, testable command execution architecture.

This is Part 2 of Issue #20 - CommandRunner Pattern Implementation

Background

Following successful APT CommandRunner migration (Issue #27), implement the same architectural patterns for Snap package manager to achieve full consistency across the codebase.

Current State

• Snap: Uses direct exec.Command calls
• APT: ✅ Uses CommandRunner (Issue APT CommandRunner Migration (Issue #20 Part 1) #27 completed)
• YUM: ✅ Uses CommandRunner (already implemented)
• Flatpak: Uses direct exec.Command calls (Issue Implement CommandRunner pattern for unified testable package manager operations #20-3)

Scope

• Snap package manager migration from exec.Command to CommandRunner
• Constructor standardization following APT/YUM patterns
• Dependency injection for comprehensive testing capabilities
• Test coverage expansion (currently 0% coverage for Snap)

Technical Implementation

CommandRunner Integration

• Replace all exec.Command calls with CommandRunner interface
• Implement automatic LC_ALL=C handling for consistent English output
• Add built-in interactive mode support via RunInteractive()
• Enable dependency injection for testing

Constructor Pattern

Following APT/YUM standardization:

• NewPackageManager() - Production use with default CommandRunner
• NewPackageManagerWithCustomRunner() - Testing use with mock CommandRunner

Testing Infrastructure

• Implement comprehensive mock-based testing
• Add environment variable tracking capabilities
• Create cross-platform test scenarios
• Achieve significant test coverage improvement (currently 0%)

Benefits

Architecture Benefits

• ✅ Consistent interface - Same CommandRunner pattern across all package managers
• ✅ Automatic LC_ALL=C - No manual environment setup needed
• ✅ Built-in interactive support - Proper stdin/stdout/stderr handling
• ✅ Unified testing approach - Same mocking patterns across codebase

Testing Benefits

• ✅ Simple mocking - Map-based command mocking vs complex setup
• ✅ Environment testing - Built-in environment variable verification
• ✅ Cross-platform testing - Same tests work across all environments
• ✅ Comprehensive coverage - All command execution paths testable

Acceptance Criteria

• Snap migrated from direct exec.Command to CommandRunner
• Constructor naming follows APT/YUM patterns
• Dependency injection implemented for testing
• Comprehensive test coverage added (target: >80%)
• LC_ALL=C automatically handled
• Interactive mode works consistently
• All existing functionality preserved
• Documentation updated

Priority

Medium Priority - Important architectural consistency improvement, but lower priority than core APT/YUM functionality.

Dependencies

• Requires Issue APT CommandRunner Migration (Issue #20 Part 1) #27 (APT CommandRunner Migration) completion
• Should follow same patterns established in APT migration

Related Issues

• Part of Issue Implement CommandRunner pattern for unified testable package manager operations #20 - CommandRunner Pattern Implementation
• Preceded by Issue APT CommandRunner Migration (Issue #20 Part 1) #27 (APT CommandRunner Migration)
• Followed by Issue Implement CommandRunner pattern for unified testable package manager operations #20-3 (Flatpak CommandRunner Migration)

Implementation Notes

• Follow proven patterns from APT migration (Issue APT CommandRunner Migration (Issue #20 Part 1) #27)
• Leverage existing CommandRunner interface and MockCommandRunner
• Maintain backward compatibility during migration
• Use established testing frameworks and patterns

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Update: Test Coverage Goals Added

Additional Scope: This issue should also address Snap's 0% test coverage.

Current Status

• Snap test coverage: 0% (needs comprehensive test suite)
• APT test coverage: 60% (good baseline achieved)
• YUM test coverage: 69.4% (good, with some gaps in Issue Improve YUM test coverage for ListInstalled, Clean, and GetPackageInfo methods #32)

Enhanced Acceptance Criteria

In addition to CommandRunner migration, this issue should include:

• Create comprehensive test suite for Snap package manager
• Target test coverage: >80% (matching or exceeding APT/YUM)
• Test all core methods: Install, Remove, Find, ListInstalled, etc.
• Mock-based testing: Use MockCommandRunner for cross-platform testing
• Fixture-based tests: Use real snap command outputs where appropriate
• Behavior testing: Follow testing philosophy focusing on contracts

Benefits

This combined approach will achieve:

1. Architectural consistency (CommandRunner pattern)
2. Test coverage parity with APT and YUM
3. Reliable CI/CD pipeline for Snap operations
4. Cross-platform testing capabilities

Combining CommandRunner migration with test coverage improvement makes this a comprehensive upgrade for the Snap package manager.