feat: auto npm install in dev mode to sync dependencies (#94)

tests/test_dev_mode.py

@@ -0,0 +1,76 @@
+"""Tests for dev mode functionality in the server."""
+
+import subprocess
+from unittest.mock import patch, MagicMock
+import pytest
+
+
+class TestEnsureNpmDependencies:
+    """Tests for ensure_npm_dependencies function."""
+
+    def test_npm_install_success_unix(self):
+        """Test npm install succeeds on Unix-like systems."""
+        from src.server.main import ensure_npm_dependencies
+        
+        with patch("platform.system", return_value="Darwin"), \
+             patch("subprocess.run") as mock_run:
+            mock_run.return_value = MagicMock(returncode=0)
+            
+            result = ensure_npm_dependencies("/fake/web/dir")
+            
+            assert result is True
+            mock_run.assert_called_once_with(
+                ["npm", "install"],
+                cwd="/fake/web/dir",
+                shell=False,
+                check=True
+            )
+
+    def test_npm_install_success_windows(self):
+        """Test npm install succeeds on Windows."""
+        from src.server.main import ensure_npm_dependencies
+        
+        with patch("platform.system", return_value="Windows"), \
+             patch("subprocess.run") as mock_run:
+            mock_run.return_value = MagicMock(returncode=0)
+            
+            result = ensure_npm_dependencies("/fake/web/dir")
+            
+            assert result is True
+            mock_run.assert_called_once_with(
+                "npm install",
+                cwd="/fake/web/dir",
+                shell=True,
+                check=True
+            )
+
+    def test_npm_install_failure_returns_false(self):
+        """Test npm install failure returns False but doesn't raise."""
+        from src.server.main import ensure_npm_dependencies
+        
+        with patch("platform.system", return_value="Darwin"), \
+             patch("subprocess.run") as mock_run:
+            mock_run.side_effect = subprocess.CalledProcessError(1, "npm install")
+            
+            result = ensure_npm_dependencies("/fake/web/dir")
+            
+            assert result is False
+
+    def test_npm_install_linux(self):
+        """Test npm install on Linux uses same path as macOS."""
+        from src.server.main import ensure_npm_dependencies
+        
+        with patch("platform.system", return_value="Linux"), \
+             patch("subprocess.run") as mock_run:
+            mock_run.return_value = MagicMock(returncode=0)
+            
+            result = ensure_npm_dependencies("/fake/web/dir")
+            
+            assert result is True
+            # Linux should use the same non-shell approach as macOS.
+            mock_run.assert_called_once_with(
+                ["npm", "install"],
+                cwd="/fake/web/dir",
+                shell=False,
+                check=True
+            )