# MockUpstream Test Verification

## Summary
Verified all MockUpstream server scenarios and methods work correctly via comprehensive test suite.

## Test Results

### All Scenario Tests (TestMockUpstream_AllScenarios)
✅ All 12 scenarios verified:
- `429-with-retry-after-then-success` - Returns 429 with Retry-After header for N requests, then succeeds
- `429-no-header-then-429` - Always returns 429 without Retry-After header
- `empty-json-body` - Returns 200 OK with empty body (triggers retry logic)
- `invalid-json-body` - Returns 200 OK with malformed JSON (triggers retry logic)
- `empty-streaming` - Returns 200 OK with empty SSE stream (triggers retry logic)
- `422-no-retry` - Returns 422 without retry (correct error code passthrough)
- `500-no-retry` - Returns 500 without retry (correct error code passthrough)
- `404-no-retry` - Returns 404 without retry (correct error code passthrough)
- `network-error-then-success` - Simulates connection failures, then succeeds
- `success` - Returns successful JSON response immediately
- `malformed-streaming` - Returns invalid SSE format (triggers retry logic)

### All Method Tests (TestMockUpstream_Methods)
✅ All 6 methods verified:
- `GetRequestCount()` - Accurately tracks and returns request count
- `SetFailUntilCount()` - Correctly configures failure behavior
- `SetRetryAfter()` - Sets Retry-After header value
- `SetDelayMs()` - Adds response delay (verified 100ms delay took ~100.5ms)
- `SetCustomHandler()` - Overrides default scenario behavior
- `ResetCounters()` - Resets counters to 0

### Proxy Integration Tests (TestMockUpstream_ProxyIntegration)
✅ All 9 integration scenarios verified:
- Success through proxy (1 upstream call, fast completion)
- 429 with retry-after through proxy (2 calls, ~2s delay with Retry-After: 1)
- Empty JSON body triggers retry (2 calls, returns 502)
- Invalid JSON body triggers retry (2 calls, returns 502)
- Empty streaming triggers retry (2 calls, returns 502)
- 422 no retry through proxy (1 call, passes through 422)
- 500 no retry through proxy (1 call, passes through 500)
- 404 no retry through proxy (1 call, passes through 404)

## Test Execution
All tests passed successfully:
```
go test -v -run TestMockUpstream ./proxy/
PASS: TestMockUpstream_AllScenarios (0.00s)
PASS: TestMockUpstream_Methods (0.10s)
PASS: TestMockUpstream_ProxyIntegration (5.01s)
```

## Coverage
The test suite provides comprehensive coverage of:
- Direct mock server behavior (via HTTP requests to mock server)
- Mock server configuration methods
- Integration with proxy handler and retry logic
- Prometheus metrics verification for error scenarios

## Files
- Implementation: `/home/coding/zai-proxy/proxy/helpers_test.go` (lines 63-246)
- Tests: `/home/coding/zai-proxy/proxy/mockupstream_test.go`