diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..ba235ee
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,167 @@
+"""Integration tests for CLI commands."""
+
+import pytest
+import json
+from pathlib import Path
+from typer.testing import CliRunner
+
+from config_convert.cli import app
+
+
+class TestCLIConvert:
+    @pytest.fixture
+    def runner(self):
+        return CliRunner()
+
+    def test_convert_json_to_yaml(self, runner, tmp_path):
+        input_file = tmp_path / "input.json"
+        input_file.write_text('{"name": "test", "value": 123}')
+        output_file = tmp_path / "output.yaml"
+        result = runner.invoke(app, ["convert", str(input_file), "--to", "yaml", "-o", str(output_file)])
+        assert result.exit_code == 0
+        assert output_file.exists()
+        content = output_file.read_text()
+        assert "name: test" in content
+
+    def test_convert_yaml_to_json(self, runner, tmp_path):
+        input_file = tmp_path / "input.yaml"
+        input_file.write_text("name: test\nvalue: 123")
+        output_file = tmp_path / "output.json"
+        result = runner.invoke(app, ["convert", str(input_file), "--from", "yaml", "--to", "json", "-o", str(output_file)])
+        assert result.exit_code == 0
+        data = json.loads(output_file.read_text())
+        assert data == {"name": "test", "value": 123}
+
+    def test_convert_env_to_json(self, runner, tmp_path):
+        input_file = tmp_path / "input.env"
+        input_file.write_text("NAME=test\nENABLED=true")
+        output_file = tmp_path / "output.json"
+        result = runner.invoke(app, ["convert", str(input_file), "--from", "env", "--to", "json", "-o", str(output_file)])
+        assert result.exit_code == 0
+        data = json.loads(output_file.read_text())
+        assert data["NAME"] == "test"
+        assert data["ENABLED"] is True
+
+    def test_convert_with_stdin(self, runner, tmp_path):
+        output_file = tmp_path / "output.json"
+        result = runner.invoke(app, ["convert", "--stdin", "--from", "json", "--to", "json", "-o", str(output_file)], input='{"name": "stdin-test"}')
+        assert result.exit_code == 0
+        data = json.loads(output_file.read_text())
+        assert data["name"] == "stdin-test"
+
+    def test_convert_missing_input(self, runner):
+        result = runner.invoke(app, ["convert", "--to", "yaml"])
+        assert result.exit_code == 2
+
+    def test_convert_invalid_format(self, runner, tmp_path):
+        input_file = tmp_path / "input.json"
+        input_file.write_text("{}")
+        result = runner.invoke(app, ["convert", str(input_file), "--to", "invalid"])
+        assert result.exit_code == 2
+
+    def test_convert_unsupported_format(self, runner, tmp_path):
+        input_file = tmp_path / "input.xml"
+        input_file.write_text("<test/>")
+        result = runner.invoke(app, ["convert", str(input_file), "--to", "yaml"])
+        assert result.exit_code == 2
+
+
+class TestCLIValidate:
+    @pytest.fixture
+    def runner(self):
+        return CliRunner()
+
+    def test_validate_valid_json(self, runner, tmp_path):
+        input_file = tmp_path / "valid.json"
+        input_file.write_text('{"name": "test"}')
+        result = runner.invoke(app, ["validate", str(input_file)])
+        assert result.exit_code == 0
+        assert "Valid" in result.output
+
+    def test_validate_invalid_json(self, runner, tmp_path):
+        input_file = tmp_path / "invalid.json"
+        input_file.write_text("{invalid}")
+        result = runner.invoke(app, ["validate", str(input_file)])
+        assert result.exit_code == 4
+        assert "Invalid" in result.output
+
+    def test_validate_valid_yaml(self, runner, tmp_path):
+        input_file = tmp_path / "valid.yaml"
+        input_file.write_text("name: test")
+        result = runner.invoke(app, ["validate", str(input_file)])
+        assert result.exit_code == 0
+
+    def test_validate_with_stdin(self, runner):
+        result = runner.invoke(app, ["validate", "--stdin", "--format", "json"], input='{"name": "test"}')
+        assert result.exit_code == 0
+
+
+class TestCLIFlatten:
+    @pytest.fixture
+    def runner(self):
+        return CliRunner()
+
+    def test_flatten_json_to_env(self, runner, tmp_path):
+        input_file = tmp_path / "input.json"
+        input_file.write_text('{"database": {"host": "localhost", "port": 5432}}')
+        output_file = tmp_path / "output.env"
+        result = runner.invoke(app, ["flatten", str(input_file), "--format", "env", "-o", str(output_file)])
+        assert result.exit_code == 0
+        content = output_file.read_text()
+        assert "database.host=localhost" in content
+
+    def test_flatten_with_custom_format(self, runner, tmp_path):
+        input_file = tmp_path / "input.json"
+        input_file.write_text('{"a": {"b": "c"}}')
+        output_file = tmp_path / "output.json"
+        result = runner.invoke(app, ["flatten", str(input_file), "--format", "json", "-o", str(output_file)])
+        assert result.exit_code == 0
+
+
+class TestCLIUnflatten:
+    @pytest.fixture
+    def runner(self):
+        return CliRunner()
+
+    def test_unflatten_env_to_json(self, runner, tmp_path):
+        input_file = tmp_path / "input.env"
+        input_file.write_text("DATABASE_HOST=localhost\nDATABASE_PORT=5432")
+        output_file = tmp_path / "output.json"
+        result = runner.invoke(app, ["unflatten", str(input_file), "--format", "json", "-o", str(output_file)])
+        assert result.exit_code == 0
+        data = json.loads(output_file.read_text())
+        assert data["DATABASE_HOST"] == "localhost"
+
+
+class TestCLISchema:
+    @pytest.fixture
+    def runner(self):
+        return CliRunner()
+
+    def test_generate_schema(self, runner, tmp_path):
+        input_file = tmp_path / "input.json"
+        input_file.write_text('{"name": "test", "count": 123}')
+        output_file = tmp_path / "schema.json"
+        result = runner.invoke(app, ["schema", str(input_file), "-o", str(output_file)])
+        assert result.exit_code == 0
+        schema = json.loads(output_file.read_text())
+        assert schema["type"] == "object"
+
+    def test_schema_with_stdin(self, runner, tmp_path):
+        output_file = tmp_path / "schema.json"
+        result = runner.invoke(app, ["schema", "--stdin", "-o", str(output_file)], input='{"name": "test"}')
+        assert result.exit_code == 0
+
+
+class TestCLIFormats:
+    @pytest.fixture
+    def runner(self):
+        return CliRunner()
+
+    def test_formats_command(self, runner):
+        result = runner.invoke(app, ["formats"])
+        assert result.exit_code == 0
+        assert "JSON" in result.output
+        assert "YAML" in result.output
+        assert "TOML" in result.output
+        assert "ENV" in result.output