Add sys import to test files and remove obsolete integration tests

- Add sys import to 29 test files across agent-coordinator, blockchain-event-bridge, blockchain-node, and coordinator-api
- Remove apps/blockchain-event-bridge/tests/test_integration.py (obsolete bridge integration tests)
- Remove apps/coordinator-api/tests/test_integration.py (obsolete API integration tests)
- Implement GPU registration in marketplace_gpu.py with GPURegistry model persistence

apps/simple-explorer/tests/test_integration_simple_explorer.py

@@ -0,0 +1,170 @@
+"""Integration tests for simple explorer service"""
+
+import pytest
+import sys
+import sys
+from pathlib import Path
+from unittest.mock import Mock, patch, AsyncMock
+from fastapi.testclient import TestClient
+
+
+# Mock httpx before importing
+sys.modules['httpx'] = Mock()
+
+from main import app
+
+
+@pytest.mark.integration
+def test_root_endpoint():
+    """Test root endpoint serves HTML"""
+    client = TestClient(app)
+    response = client.get("/")
+    assert response.status_code == 200
+    assert "text/html" in response.headers["content-type"]
+    assert "AITBC Blockchain Explorer" in response.text
+
+
+@pytest.mark.integration
+def test_get_chain_head_success():
+    """Test /api/chain/head endpoint with successful response"""
+    client = TestClient(app)
+    
+    mock_response = Mock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {"height": 100, "hash": "0xabc123", "timestamp": 1234567890}
+    
+    mock_client = AsyncMock()
+    mock_client.__aenter__.return_value = mock_client
+    mock_client.get.return_value = mock_response
+    
+    with patch('main.httpx.AsyncClient', return_value=mock_client):
+        response = client.get("/api/chain/head")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["height"] == 100
+        assert data["hash"] == "0xabc123"
+
+
+@pytest.mark.integration
+def test_get_chain_head_error():
+    """Test /api/chain/head endpoint with error"""
+    client = TestClient(app)
+    
+    mock_client = AsyncMock()
+    mock_client.__aenter__.return_value = mock_client
+    mock_client.get.side_effect = Exception("RPC error")
+    
+    with patch('main.httpx.AsyncClient', return_value=mock_client):
+        response = client.get("/api/chain/head")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["height"] == 0
+        assert data["hash"] == ""
+
+
+@pytest.mark.integration
+def test_get_block_success():
+    """Test /api/blocks/{height} endpoint with successful response"""
+    client = TestClient(app)
+    
+    mock_response = Mock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {
+        "height": 50,
+        "hash": "0xblock50",
+        "timestamp": 1234567890,
+        "transactions": []
+    }
+    
+    mock_client = AsyncMock()
+    mock_client.__aenter__.return_value = mock_client
+    mock_client.get.return_value = mock_response
+    
+    with patch('main.httpx.AsyncClient', return_value=mock_client):
+        response = client.get("/api/blocks/50")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["height"] == 50
+        assert data["hash"] == "0xblock50"
+
+
+@pytest.mark.integration
+def test_get_block_error():
+    """Test /api/blocks/{height} endpoint with error"""
+    client = TestClient(app)
+    
+    mock_client = AsyncMock()
+    mock_client.__aenter__.return_value = mock_client
+    mock_client.get.side_effect = Exception("RPC error")
+    
+    with patch('main.httpx.AsyncClient', return_value=mock_client):
+        response = client.get("/api/blocks/50")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["height"] == 50
+        assert data["hash"] == ""
+
+
+@pytest.mark.integration
+def test_get_transaction_success():
+    """Test /api/transactions/{tx_hash} endpoint with successful response"""
+    client = TestClient(app)
+    
+    mock_response = Mock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {
+        "tx_hash": "0x" + "a" * 64,
+        "sender": "0xsender",
+        "recipient": "0xrecipient",
+        "payload": {
+            "value": "1000",
+            "fee": "10"
+        },
+        "created_at": "2026-01-01T00:00:00",
+        "block_height": 100
+    }
+    
+    mock_client = AsyncMock()
+    mock_client.__aenter__.return_value = mock_client
+    mock_client.get.return_value = mock_response
+    
+    with patch('main.httpx.AsyncClient', return_value=mock_client):
+        response = client.get("/api/transactions/" + "a" * 64)
+        assert response.status_code == 200
+        data = response.json()
+        assert data["hash"] == "0x" + "a" * 64
+        assert data["from"] == "0xsender"
+        assert data["to"] == "0xrecipient"
+        assert data["amount"] == "1000"
+        assert data["fee"] == "10"
+
+
+@pytest.mark.integration
+def test_get_transaction_not_found():
+    """Test /api/transactions/{tx_hash} endpoint with 404 response"""
+    client = TestClient(app)
+    
+    mock_response = Mock()
+    mock_response.status_code = 404
+    
+    mock_client = AsyncMock()
+    mock_client.__aenter__.return_value = mock_client
+    mock_client.get.return_value = mock_response
+    
+    with patch('main.httpx.AsyncClient', return_value=mock_client):
+        response = client.get("/api/transactions/" + "a" * 64)
+        assert response.status_code == 404
+
+
+@pytest.mark.integration
+def test_get_transaction_error():
+    """Test /api/transactions/{tx_hash} endpoint with error"""
+    client = TestClient(app)
+    
+    mock_client = AsyncMock()
+    mock_client.__aenter__.return_value = mock_client
+    mock_client.get.side_effect = Exception("RPC error")
+    
+    with patch('main.httpx.AsyncClient', return_value=mock_client):
+        response = client.get("/api/transactions/" + "a" * 64)
+        assert response.status_code == 500