Add comprehensive tests for the agent package

[Copilot]

This PR adds a complete test suite for the agent package, which previously had no test coverage. The implementation provides thorough testing of all core agent functionality with 89.5% code coverage.

What's Added

Test Files Created:

• agent_test.go - Agent creation, builder pattern, and basic methods
• system_message_test.go - System message generation with various configurations
• run_test.go - Agent execution workflow including tool calling
• run_response_test.go - RunResponse building and parameter handling
• errors_test.go - Error handling for various failure scenarios
• delegate_task_test.go - Task delegation to subordinate agents
• run_streaming_test.go - Streaming execution functionality

Key Testing Areas Covered

Agent Creation & Builder Pattern

Tests all With* option functions including WithName, WithDescription, WithRole, WithInstructions, WithGoal, WithExpectedOutput, WithTool, WithSubordinate, and WithChatOptions.

System Message Generation

Comprehensive testing of system message computation with:

• Basic agent properties (name, description, instructions, goal, expected output)
• Subordinate agent integration with proper formatting
• Error handling for subordinate failures
• XML tag formatting validation

Agent Execution Workflow

• Message handling with automatic system message injection
• Tool calling and execution with proper error handling
• Parallel tool execution with result ordering
• Model response processing and metrics collection
• Both synchronous and streaming execution modes

Task Delegation

• Delegation to single and multiple subordinate agents
• Parallel subordinate execution with proper synchronization
• Error handling and reporting from subordinates
• Parameter validation for delegation requests

Error Scenarios

• Builder parameter validation
• Model response error handling
• Tool execution failures
• Subordinate agent errors
• Invalid delegation parameters

Testing Strategy

The tests use comprehensive mocking to avoid external dependencies:

• Mock LLM providers with configurable responses and errors
• Mock subordinate agents with customizable behavior
• Mock tools for testing tool execution workflows
• Structured test scenarios covering both happy paths and error conditions

All tests follow Go testing best practices with clear test names, proper setup/teardown, and thorough assertions using the testify framework.

Coverage

Achieves 89.5% code coverage across the agent package, ensuring robust testing of:

• All public APIs and methods
• Error handling paths
• Complex workflows like tool calling and task delegation
• Edge cases and boundary conditions

This comprehensive test suite provides confidence in the agent package functionality and will help prevent regressions as the codebase evolves.

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