[Enhancement] Add comprehensive failure testing infrastructure

[EricSanchezok]

Summary

AWCP needs comprehensive failure testing. Current tests cover happy paths but lack systematic coverage of failure scenarios.

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Current Coverage Gap

Tested: State machine transitions, admission control, basic SSE retry

Not Tested: Network failures, transport failures, SSE interruption, race conditions, data integrity

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Proposed Test Structure

packages/sdk/test/
├── unit/           # Existing tests
├── component/      # New: isolated failure injection
│   ├── sse-failures.test.ts
│   ├── transport-failures.test.ts
│   └── network-failures.test.ts
└── integration/    # New: end-to-end with faults
    └── recovery-scenarios.test.ts

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Key Test Cases (Priority Order)

P0 - Critical

• SSE connection drop + retry exhausted
• SSE timeout (no events received)
• Transport checksum mismatch
• Network timeout on INVITE/START
• Executor unreachable (ECONNREFUSED)

P1 - Important

• HTTP error responses (401, 429, 500, 502, 503)
• Transport setup failures (mount, extraction)
• Cancel during task execution
• Recovery via GET /tasks/:id/result

P2 - Nice to Have

• Malformed JSON responses
• State machine invalid transitions
• Partial upload/download failures

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Recommended Dependencies

{
  "devDependencies": {
    "nock": "^13.5.0",
    "get-port": "^7.0.0"
  }
}

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Example: SSE Failure Test

it('should retry on connection drop', async () => {
  let attempts = 0;
  server = createServer((req, res) => {
    attempts++;
    res.writeHead(200, { 'Content-Type': 'text/event-stream' });
    res.destroy(); // Drop connection
  }).listen(port);

  const client = new ExecutorClient({ sseMaxRetries: 3, sseRetryDelayMs: 10 });
  
  await expect(async () => {
    for await (const _ of client.subscribeTask(`http://localhost:${port}`, 'test')) {}
  }).rejects.toThrow();

  expect(attempts).toBe(4); // 1 + 3 retries
});

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Checklist

• Add nock, get-port dependencies
• Create component test directory structure
• Implement P0 test cases
• Implement P1 test cases
• Add to CI pipeline