test: add coverage for _print_npm_not_found_help function

Tests cover all three OS-specific branches:
- Windows instructions
- macOS instructions
- Linux instructions (including fallback for unknown OS)

Author: bigcat88

tests/comfy_cli/command/test_install.py

@@ -0,0 +1,76 @@
+"""Tests for install command functionality"""
+
+from io import StringIO
+from unittest.mock import patch
+
+import pytest
+
+from comfy_cli.command.install import _print_npm_not_found_help
+
+
+class TestPrintNpmNotFoundHelp:
+    """Tests for _print_npm_not_found_help function"""
+
+    @pytest.fixture
+    def capture_output(self):
+        """Fixture to capture rich console output"""
+        output = StringIO()
+        with patch(
+            "comfy_cli.command.install.rprint",
+            side_effect=lambda *args: output.write(str(args[0]) + "\n" if args else "\n"),
+        ):
+            yield output
+
+    def test_npm_not_found_help_shows_common_message(self, capture_output):
+        """Test that common npm not found message is shown regardless of OS"""
+        with patch("platform.system", return_value="Linux"):
+            _print_npm_not_found_help("v20.0.0")
+
+        output_text = capture_output.getvalue()
+        assert "npm is not installed or not found in PATH" in output_text
+        assert "npm is a package manager that usually comes bundled with Node.js" in output_text
+        assert "v20.0.0" in output_text
+        assert "After fixing npm, run your comfy command again" in output_text
+
+    def test_npm_not_found_help_windows(self, capture_output):
+        """Test Windows-specific instructions"""
+        with patch("platform.system", return_value="Windows"):
+            _print_npm_not_found_help("v18.17.0")
+
+        output_text = capture_output.getvalue()
+        assert "How to fix this on Windows" in output_text
+        assert "Add or remove programs" in output_text
+        assert "Command Prompt or PowerShell" in output_text
+
+    def test_npm_not_found_help_macos(self, capture_output):
+        """Test macOS-specific instructions"""
+        with patch("platform.system", return_value="Darwin"):
+            _print_npm_not_found_help("v18.17.0")
+
+        output_text = capture_output.getvalue()
+        assert "How to fix this on macOS" in output_text
+        assert "Homebrew" in output_text
+        assert "brew install node" in output_text
+        assert ".pkg file" in output_text
+        assert "Cmd+Q" in output_text
+
+    def test_npm_not_found_help_linux(self, capture_output):
+        """Test Linux-specific instructions"""
+        with patch("platform.system", return_value="Linux"):
+            _print_npm_not_found_help("v18.17.0")
+
+        output_text = capture_output.getvalue()
+        assert "How to fix this on Linux" in output_text
+        assert "sudo apt" in output_text
+        assert "Ubuntu/Debian" in output_text
+        assert "Fedora" in output_text
+        assert "NodeSource" in output_text
+
+    def test_npm_not_found_help_unknown_os_falls_back_to_linux(self, capture_output):
+        """Test that unknown OS falls back to Linux instructions"""
+        with patch("platform.system", return_value="FreeBSD"):
+            _print_npm_not_found_help("v18.17.0")
+
+        output_text = capture_output.getvalue()
+        # Should show Linux instructions as fallback
+        assert "How to fix this on Linux" in output_text