Refactor: Move backend files to backend/ directory and split .gitignore

backend/tests/test_coder.py

@@ -0,0 +1,62 @@
+import pytest
+from unittest.mock import MagicMock, patch
+from ea_chatbot.graph.nodes.coder import coder_node
+from ea_chatbot.graph.nodes.error_corrector import error_corrector_node
+
+@pytest.fixture
+def mock_state():
+    return {
+        "messages": [],
+        "question": "Show me results for New Jersey",
+        "plan": "Step 1: Load data\nStep 2: Filter by NJ",
+        "code": None,
+        "error": None,
+        "plots": [],
+        "dfs": {},
+        "next_action": "plan"
+    }
+
+@patch("ea_chatbot.graph.nodes.coder.get_llm_model")
+@patch("ea_chatbot.utils.database_inspection.get_data_summary")
+def test_coder_node(mock_get_summary, mock_get_llm, mock_state):
+    """Test coder node generates code from plan."""
+    mock_get_summary.return_value = "Column: Name, Type: text"
+    
+    mock_llm = MagicMock()
+    mock_get_llm.return_value = mock_llm
+    
+    from ea_chatbot.schemas import CodeGenerationResponse
+    mock_response = CodeGenerationResponse(
+        code="import pandas as pd\nprint('Hello')",
+        explanation="Generated code"
+    )
+    mock_llm.with_structured_output.return_value.invoke.return_value = mock_response
+    
+    result = coder_node(mock_state)
+    
+    assert "code" in result
+    assert "import pandas as pd" in result["code"]
+    assert "error" in result
+    assert result["error"] is None
+
+@patch("ea_chatbot.graph.nodes.error_corrector.get_llm_model")
+def test_error_corrector_node(mock_get_llm, mock_state):
+    """Test error corrector node fixes code."""
+    mock_state["code"] = "import pandas as pd\nprint(undefined_var)"
+    mock_state["error"] = "NameError: name 'undefined_var' is not defined"
+    
+    mock_llm = MagicMock()
+    mock_get_llm.return_value = mock_llm
+    
+    from ea_chatbot.schemas import CodeGenerationResponse
+    mock_response = CodeGenerationResponse(
+        code="import pandas as pd\nprint('Defined')",
+        explanation="Fixed variable"
+    )
+    mock_llm.with_structured_output.return_value.invoke.return_value = mock_response
+    
+    result = error_corrector_node(mock_state)
+    
+    assert "code" in result
+    assert "print('Defined')" in result["code"]
+    assert result["error"] is None