diff --git a/tests/integration/test_execution_flow.py b/tests/integration/test_execution_flow.py
index a3a566d..c749475 100644
--- a/tests/integration/test_execution_flow.py
+++ b/tests/integration/test_execution_flow.py
@@ -1,12 +1,70 @@
 """Integration tests for end-to-end execution flows."""
 
 import pytest
+from unittest.mock import Mock, MagicMock, patch
+
+from pod_executor import CodeExecutor, ExecutionResult, ResourceLimits
+from pod_executor.containers.manager import SecureContainerManager
+from mcp_forge.adapters import SimpleBackend, JupyterBackend
 
 
 @pytest.mark.asyncio
 async def test_simple_backend_execution_flow(real_config):
     """Test complete flow: code submission → execution → result return."""
-    pytest.skip("TODO: Phase 5.4 - Requires proper container registration and security setup")
+    # Mock the container manager
+    mock_container_manager = Mock(spec=SecureContainerManager)
+    mock_container_manager.create_container.return_value = "test-container-123"
+    mock_container_manager.wait_for_container.return_value = 0
+    mock_container_manager.get_container_logs.return_value = (
+        '{"result": 42, "error": null}',
+        ""
+    )
+    
+    # Create audit logger mock
+    from mcp_forge.security.audit import AuditLogger
+    mock_audit_logger = Mock(spec=AuditLogger)
+    
+    # Create simple backend
+    backend = SimpleBackend(
+        container_manager=mock_container_manager,
+        audit_logger=mock_audit_logger,
+        config=real_config
+    )
+    
+    # Execute code
+    result = backend.execute("print(21 * 2)")
+    
+    # Verify execution worked
+    assert result.success is True
+    assert result.exit_code == 0
+    
+    # Verify container lifecycle was called
+    mock_container_manager.create_container.assert_called_once()
+    mock_container_manager.start_container.assert_called_once()
+    mock_container_manager.remove_container.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_jupyter_backend_initialization(real_config):
+    """Test Jupyter backend can be initialized with adapters."""
+    # Mock the container manager
+    mock_container_manager = Mock(spec=SecureContainerManager)
+    
+    # Create audit logger mock
+    from mcp_forge.security.audit import AuditLogger
+    mock_audit_logger = Mock(spec=AuditLogger)
+    
+    # Create jupyter backend (should not raise)
+    backend = JupyterBackend(
+        container_manager=mock_container_manager,
+        audit_logger=mock_audit_logger,
+        config=real_config
+    )
+    
+    # Verify backend was created
+    assert backend is not None
+    assert backend.backend is not None
+    assert backend.config == real_config
 
 
 @pytest.mark.asyncio