obsidian-vault/work/wiki/apple-browsers/network-quality-testing.md

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~/DuckDuckGo/apple-browsers.git/main/.cursor/rules/network-quality-testing.mdc	0.9	work	2026-04-28	false

NetworkQualityMonitor Testing Framework

Overview

The NetworkQualityMonitor is a comprehensive network quality testing framework designed for the DuckDuckGo Privacy Browser. It provides pre-flight network connectivity and performance checks to ensure optimal browser performance.

Architecture Principles

SOLID Design

• Single Responsibility: Each tester handles one specific network metric
• Open/Closed: Protocol-based design allows extension without modification
• Dependency Injection: All dependencies injected for testability
• Interface Segregation: Focused protocols for each test type

Component Structure

NetworkQualityMonitor (Orchestrator)
├── HttpResponseTester (Latency)
├── BandwidthTester (Speed)
├── DNSTester (Resolution)
├── BufferBloatTester (Congestion)
└── NetworkScoreCalculator (Scoring)

Test Implementation Details

HTTP Response Testing (Latency)

• Multi-endpoint sampling: Tests CDN endpoints (CloudFlare, Fastly, CloudFront)
• Statistical analysis: Calculates median, mean, standard deviation, CV
• Smart aggregation: Best site selection with weighted penalties
• Metrics: P50/P95 percentiles, variance, failure rate

Bandwidth Testing

• Server selection: Quick 10MB test, then full test on best servers
• Download measurement: Multiple runs, returns maximum speed
• Upload measurement: Chunked uploads (50MB x 2)
• Optimization: Range requests, cache-busting, timeout protection

DNS Testing

• Domain resolution: Popular domains (google.com, cloudflare.com)
• Timing precision: CFAbsoluteTime for microsecond accuracy
• Failure tracking: Resolution success/failure rates
• System resolver: Uses native DNS resolution

Buffer Bloat Testing

• Baseline measurement: Unloaded network latency
• Load testing: Concurrent downloads during latency measurement
• Grade assignment: A-F based on latency increase percentage
• Real-time impact: Critical for video calls, gaming

Scoring Algorithm

Component Weights

• HTTP Response: 25%
• Bandwidth: 35%
• DNS: 15%
• Buffer Bloat: 25%

Quality Ratings

• Excellent (80-100): Optimal performance
• Good (60-79): Good for most tasks
• Fair (40-59): May experience issues
• Poor (0-39): Significant issues likely

Testing Best Practices

Unit Testing

// Use protocol-based mocks
class MockHttpResponseTester: HttpResponseTesting {
    func performTest(...) async throws -> HttpResponseResult {
        // Return deterministic results
    }
}

Integration Testing

• Mock NetworkSession for controlled responses
• Test error scenarios and edge cases
• Verify progress callback behavior

Performance Testing

• Monitor memory usage during large downloads
• Verify timeout handling
• Test concurrent execution

Usage Patterns

Basic Implementation

let monitor = NetworkQualityMonitor()
let results = try await monitor.runTest()
print("Quality: \(results.quality.rawValue)")

With Progress Reporting

monitor.progressCallback = { progress, message in
    // Update UI with progress
}

Custom Configuration

let config = TestConfiguration(
    latencyTestURLs: customURLs,
    latencySamplesPerEndpoint: 20
)
let monitor = NetworkQualityMonitor(configuration: config)

Security Considerations

• HTTPS only: All endpoints use secure connections
• No user data: Only generic test payloads
• Certificate validation: Standard validation enabled
• Rate limiting: Built-in delays between samples

Error Handling

Error Types

• invalidResponse: HTTP errors, malformed data
• allTestsFailed: Complete connectivity loss
• insufficientData: Not enough samples collected
• timeout: Test exceeded time limit

Recovery Strategies

• Continue testing if individual endpoints fail
• Provide partial results when possible
• Clear error reporting with localized descriptions

Performance Optimizations

• HEAD requests: Minimal data for latency tests
• Range requests: Efficient server selection
• Connection reuse: URLSession connection pooling
• Memory streaming: Large downloads streamed, not buffered

Package Integration

Adding to Project

1. Add NetworkQualityMonitor package dependency
2. Import NetworkQualityMonitor module
3. Initialize with configuration
4. Handle async test execution

Debug Menu Integration

• Available under Debug → Network Quality
• Individual test execution
• Detailed result display

Future Enhancements

• IPv6 testing separation
• Jitter analysis
• Packet loss detection
• Geographic server selection
• Historical trending