Focus 3: Test Coverage

[rainliu]

Focus 3: Test Coverage

Current State

The codebase has growing test coverage, but there's room for improvement:

Category	Current	Target
Unit tests	Partial	80%+ line coverage
Integration tests	28 test files	Comprehensive scenarios
Interop tests	Chrome, Firefox	All major browsers
Fuzz tests	Limited	Critical parsers

Unit Test Expansion

Priority areas for unit testing:

1. SDP parsing and generation — Complex edge cases in offer/answer
2. ICE state machine — All state transitions and error conditions
3. DTLS handshake — Certificate validation, cipher negotiation
4. SCTP association — Stream management, congestion control
5. Interceptor logic — NACK timing, RTCP report generation

Example test structure:

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_ice_state_transitions() {
        // Test all valid state transitions
        // Test invalid transition handling
        // Test event emission
    }

    #[test]
    fn test_nack_timing_accuracy() {
        // Verify NACK generation timing
        // Test RTT-based retransmit intervals
    }
}

Integration Test Expansion

Planned integration test scenarios:

• Multi-party conferencing (3+ peers)
• Renegotiation (adding/removing tracks mid-session)
• Network condition simulation (packet loss, delay, reordering)
• Long-running sessions (stability over hours)
• ICE restart scenarios
• TURN relay failover
• Simulcast layer switching
• DataChannel flow control under load

Fuzz Testing

Critical parsers should be fuzz-tested:

// Using cargo-fuzz or libfuzzer
fuzz_target!(|data: &[u8]| {
    let _ = RtpPacket::unmarshal(data);
});

fuzz_target!(|data: &[u8]| {
    let _ = StunMessage::unmarshal(data);
});

Priority fuzz targets:

• RTP/RTCP packet parsing
• STUN message parsing
• SDP parsing
• SCTP chunk parsing
• DTLS record parsing