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Testing PR #2: Yahoo Integration Tests

✅ What Was Added

Problem: No end-to-end integration tests verified the full Yahoo fetch flow. Tests only covered helper functions.

Solution: Added 3 comprehensive integration tests with mocked network calls.

🧪 New Tests Added

1. test_fetch_yahoo_data_full_flow

Purpose: Verifies complete flow: crumb → fetch → parse → cache → return

What it tests:

  • Mocks Yahoo crumb request
  • Mocks Yahoo chart data request
  • Verifies data parsing works correctly
  • Confirms cache file is created
  • Validates returned data format and values

2. test_fetch_yahoo_data_incremental_update

Purpose: Tests incremental cache updates (key feature for avoiding 429 errors)

What it tests:

  • Pre-populates cache with old data
  • Fetches new data range that overlaps with cache
  • Verifies old + new data are merged
  • Confirms cache strategy works as designed

3. test_fetch_yahoo_data_with_cache_disabled

Purpose: Validates use_cache=False bypass works

What it tests:

  • Pre-populates cache with dummy data
  • Fetches with use_cache=False
  • Verifies fresh data is fetched (not cached data)
  • Confirms cache bypass flag works correctly

🧪 How to Test

Test 1: Run New Integration Tests Only

pytest tests/test_yahoo.py::TestYahooIntegration -v

Expected Output:

tests/test_yahoo.py::TestYahooIntegration::test_fetch_yahoo_data_full_flow PASSED         [ 33%]
tests/test_yahoo.py::TestYahooIntegration::test_fetch_yahoo_data_incremental_update PASSED [ 66%]
tests/test_yahoo.py::TestYahooIntegration::test_fetch_yahoo_data_with_cache_disabled PASSED [100%]

============================================================== 3 passed in 0.38s ===============================================================

Test 2: Run All Yahoo Tests

pytest tests/test_yahoo.py -v

Expected Output:

16 passed in ~16s

Breakdown:

  • 5 tests: TestYahooDataFetching
  • 2 tests: TestYahooDataValidation
  • 1 test: TestYahooDataDedup
  • 3 tests: TestYahooIntegration ✨ NEW
  • 5 tests: TestPersistentCache

Test 3: Run All Project Tests

pytest tests/ -v

Expected Output:

49 passed in ~17s

Breakdown:

  • 12 tests: Backtest
  • 7 tests: Plotting (from PR #1)
  • 14 tests: Signal generation
  • 16 tests: Yahoo fetching (3 new from PR #2)

🎯 Why These Tests Matter

Problem: The 429 Rate Limit Error

When you run:

python scripts/demo_latest.py --lookback 1095 --signal v2

You see:

ERROR: Failed to fetch ES: HTTP Error 500: Failed to get Yahoo Finance crumb for ES=F:
HTTP Error 429: Too Many Requests

What This Means

429 = External Yahoo API Rate Limit

  • Yahoo Finance limits API requests per IP
  • Too many requests = temporary block
  • This is an external issue, not a code bug
  • Cache system is designed to minimize these requests

How Integration Tests Help

  1. Tests are 100% offline - No real network calls
  2. Mocked responses - Use fixture data instead of Yahoo API
  3. Fast & reliable - Run in ~0.4 seconds
  4. Verify cache logic - Ensure incremental fetch works correctly

The Cache Strategy (Tested in PR #2)

Run 1 (cold cache):  Fetch 1095 days → Save to cache
Run 2 (warm cache):  Load 1090 days from cache → Fetch only 5 new days
Run 3 (next day):    Load 1094 days from cache → Fetch only 1 new day

Result: Drastically reduces Yahoo API calls, minimizes 429 errors.

📊 Test Coverage Summary

Test Class Tests Purpose
TestYahooIntegration 3 ✨ NEW End-to-end flow with mocked network
TestPersistentCache 5 Cache save/load/merge logic
TestYahooDataFetching 5 Helper functions
TestYahooDataValidation 2 Input validation
TestYahooDataDedup 1 Duplicate handling

Total: 16 Yahoo tests, all offline, all passing

⚠️ About the 429 Error

The 429 error you're seeing is expected behavior from Yahoo Finance, not a bug in our code:

Why It Happens

  • Yahoo rate limits: ~2000 requests per hour per IP
  • Each ticker (ES, SPY) = 2 requests (crumb + data)
  • Multiple demo runs = hits limit quickly

Solutions

Option 1: Use Cached Data (Recommended)

# First run: Fetch fresh data
python scripts/demo_latest.py --lookback 1095 --signal v2

# Wait for Yahoo cooldown (1-24 hours), then run again
# Second run: Uses cache, only fetches missing days
python scripts/demo_latest.py --lookback 1095 --signal v2

Option 2: Use Synthetic Demo (No Network)

# From PR #1 - generates synthetic ES/SPY data
python scripts/pr1_synthetic_demo.py

Option 3: Wait & Retry

  • Yahoo rate limits reset after 1-24 hours
  • Use different network/VPN/proxy if urgent

Option 4: Use Smaller Lookback

# Fetch less data = fewer requests
python scripts/demo_latest.py --lookback 30 --signal v2

✅ Verification Checklist

  • 3 new integration tests added
  • All 16 Yahoo tests pass
  • All 49 project tests pass
  • Tests are 100% offline (no network dependency)
  • Tests use mocked Yahoo responses
  • Cache logic is validated
  • Incremental fetch is tested
  • Cache bypass is tested

🔍 Quick Verification (10 seconds)

# Run just the new integration tests
pytest tests/test_yahoo.py::TestYahooIntegration -v

Should show:

3 passed in 0.38s ✅

📖 Key Insight

The integration tests prove the code works correctly.
The 429 error is Yahoo's rate limiting, not a code bug.
Cache system is working as designed to minimize API calls.

When Yahoo allows requests again, the demo will work. In the meantime, use synthetic demo or cached data.