diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..eaead5c
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,146 @@
+"""Tests for CLI interface."""
+
+from pathlib import Path
+
+from click.testing import CliRunner
+
+from src.cli import main
+
+
+class TestCLI:
+    """Tests for CLI functionality."""
+
+    def test_cli_help(self):
+        """Test CLI help command."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--help"])
+        assert result.exit_code == 0
+        assert "--path" in result.output
+        assert "--language" in result.output
+        assert "--framework" in result.output
+
+    def test_cli_dry_run(self):
+        """Test CLI dry-run option."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--language", "python"])
+        assert result.exit_code == 0
+        assert "__pycache__/" in result.output
+
+    def test_cli_force_overwrite(self, temp_project_dir: Path):
+        """Test CLI force overwrite option."""
+        gitignore = temp_project_dir / ".gitignore"
+        gitignore.write_text("old content\n")
+
+        runner = CliRunner()
+        runner.invoke(main, ["--path", str(temp_project_dir), "--force", "--dry-run"])
+
+    def test_cli_output_file(self, temp_project_dir: Path):
+        """Test CLI custom output file option."""
+        output_file = temp_project_dir / "custom.gitignore"
+
+        runner = CliRunner()
+        runner.invoke(main, ["--output", str(output_file), "--language", "python", "--force"])
+
+        assert output_file.exists()
+
+    def test_cli_verbose_output(self):
+        """Test CLI verbose output option."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--language", "python", "--verbose"])
+        assert result.exit_code == 0
+        assert "python" in result.output.lower() or "Detected" in result.output
+
+    def test_cli_multiple_languages(self):
+        """Test CLI with multiple languages."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--language", "python", "--language", "nodejs"])
+        assert result.exit_code == 0
+
+    def test_cli_multiple_frameworks(self):
+        """Test CLI with multiple frameworks."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--framework", "django", "--framework", "react"])
+        assert result.exit_code == 0
+
+    def test_cli_custom_patterns(self):
+        """Test CLI with custom patterns."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--custom", "custom_dir/", "--custom", "*.custom"])
+        assert result.exit_code == 0
+        assert "custom_dir/" in result.output
+
+    def test_cli_os_patterns(self):
+        """Test CLI with OS patterns."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--os", "macos", "--os", "windows"])
+        assert result.exit_code == 0
+        assert ".DS_Store" in result.output
+        assert "Thumbs.db" in result.output
+
+    def test_cli_ide_patterns(self):
+        """Test CLI with IDE patterns."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--ide", "vscode", "--ide", "jetbrains"])
+        assert result.exit_code == 0
+        assert ".vscode/" in result.output
+        assert ".idea/" in result.output
+
+    def test_cli_nonexistent_path(self):
+        """Test CLI with nonexistent path."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--path", "/nonexistent/path"])
+        assert result.exit_code != 0
+
+    def test_cli_invalid_language(self):
+        """Test CLI with invalid language."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--language", "invalid_language"])
+        assert result.exit_code != 0
+
+    def test_cli_invalid_framework(self):
+        """Test CLI with invalid framework."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--dry-run", "--framework", "invalid_framework"])
+        assert result.exit_code != 0
+
+    def test_detect_project_stack_python(self, python_project: Path):
+        """Test project stack detection for Python project."""
+        from src.cli import detect_project_stack
+
+        stack = detect_project_stack(python_project)
+        assert "python" in stack.get("languages", [])
+
+    def test_detect_project_stack_nodejs(self, nodejs_project: Path):
+        """Test project stack detection for Node.js project."""
+        from src.cli import detect_project_stack
+
+        stack = detect_project_stack(nodejs_project)
+        assert "nodejs" in stack.get("languages", [])
+
+    def test_detect_project_stack_django(self, django_project: Path):
+        """Test project stack detection for Django project."""
+        from src.cli import detect_project_stack
+
+        stack = detect_project_stack(django_project)
+        assert "django" in stack.get("frameworks", [])
+
+    def test_detect_project_stack_react(self, react_project: Path):
+        """Test project stack detection for React project."""
+        from src.cli import detect_project_stack
+
+        stack = detect_project_stack(react_project)
+        assert "react" in stack.get("frameworks", [])
+
+    def test_detect_project_stack_vscode(self, vscode_project: Path):
+        """Test IDE detection for VSCode project."""
+        from src.cli import detect_project_stack
+
+        stack = detect_project_stack(vscode_project)
+        assert "vscode" in stack.get("ides", [])
+
+    def test_detect_project_stack_jetbrains(self, jetbrains_project: Path):
+        """Test IDE detection for JetBrains project."""
+        from src.cli import detect_project_stack
+
+        stack = detect_project_stack(jetbrains_project)
+        assert "jetbrains" in stack.get("ides", [])