Add comprehensive unit tests for federated feature

- Tests successful federation from remote endpoints
- Tests error handling (server errors, invalid JSON, timeouts)
- Tests multiple endpoint federation
- Tests duplicate check name conflict resolution
- Uses httptest.NewServer for realistic HTTP simulation
- Validates federated check marking and status reporting

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

1 files changed, 82 insertions, 0 deletions

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Gogios is a lightweight, minimalistic monitoring tool written in Go designed for small-scale server monitoring. It executes Nagios-compatible check plugins and sends email notifications when service states change.
+
+## Build and Development Commands
+
+### Build
+```bash
+# Standard build
+go build -o gogios cmd/gogios/main.go
+
+# Using taskfile
+task build
+
+# Development build with race detection
+task dev
+```
+
+### Code Quality
+```bash
+# Run go vet
+task vet
+
+# Run linter (requires golangci-lint)
+task lint
+
+# Install linter
+task lint-install
+```
+
+## Architecture
+
+### Core Components
+
+- **cmd/gogios/main.go**: Entry point with CLI argument parsing
+- **internal/run.go**: Main execution orchestrator
+- **internal/config.go**: JSON configuration file parsing and validation
+- **internal/check.go**: Individual check execution using external Nagios plugins
+- **internal/state.go**: Persistent state management (tracks check status changes)
+- **internal/runchecks.go**: Concurrent check execution with dependency handling
+- **internal/notify.go**: Email notification system
+- **internal/federated.go**: Federation support for distributed monitoring
+- **internal/nagioscode.go**: Nagios exit code constants (OK, WARNING, CRITICAL, UNKNOWN)
+- **internal/dependency.go**: Check dependency resolution
+
+### Key Design Patterns
+
+1. **State-based Notifications**: Only sends emails when check status changes, not on every run
+2. **Dependency Checks**: Supports check dependencies (e.g., don't check HTTP if ping fails)
+3. **Concurrent Execution**: Runs multiple checks simultaneously with configurable concurrency
+4. **Retry Logic**: Configurable retry attempts with intervals for failed checks
+5. **Federation**: Can merge results from multiple Gogios instances
+6. **Stale Detection**: Identifies checks that haven't run within threshold time
+
+### Configuration
+
+The tool is configured via JSON file (typically `/etc/gogios.json`) with:
+- Email settings (from/to addresses, SMTP server)
+- Check definitions (plugin path, arguments, dependencies)
+- Concurrency and timeout settings
+- State persistence directory
+
+### Execution Flow
+
+1. Load configuration and validate check dependencies
+2. Load previous state from state.json
+3. Execute checks concurrently (respecting dependencies)
+4. Merge federated results if configured
+5. Generate report and send notifications for status changes
+6. Persist new state
+
+## Development Notes
+
+- Uses standard Go project structure with internal package
+- No external dependencies beyond Go standard library
+- Designed for Unix-like systems (tested on OpenBSD)
+- Supports cross-compilation for different platforms
+- State persisted as JSON in configurable directory
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