Add tests

[simonw]

Oops:

mock_palm = <MagicMock name='palm' id='140718416327120'>

    @patch("llm_palm.palm")
    def test_palm_models(mock_palm):
        fake_models = [
            {"name": "'models/chat-bison-001"},
            {"name": "models/text-bison-001"},
        ]
        # Mock palm.list_models()
        mock_palm.list_models.return_value = fake_models
        runner = CliRunner()
        result = runner.invoke(cli, ["palm", "models"])
>       assert result.exit_code == 0, result.output
E       AssertionError: Error: No key found - add one using 'llm keys set palm' or set the PALM_API_KEY environment variable
E         
E       assert 1 == 0
E        +  where 1 = <Result SystemExit(1)>.exit_code

tests/test_llm_palm.py:33: AssertionError
_______________________________ test_palm_prompt _______________________________

mock_palm = <MagicMock name='palm' id='140718416285008'>

    @patch("llm_palm.palm")
    def test_palm_prompt(mock_palm):
        mock_response = Mock()
        mock_response.last = "🐶🐶"
        mock_palm.chat.return_value = mock_response
        runner = CliRunner()
        result = runner.invoke(cli, ["two dog emoji", "-m", "palm"])
>       assert result.exit_code == 0, result.output
E       AssertionError: Error: No key found - add one using 'llm keys set palm'
E         
E       assert 1 == 0
E        +  where 1 = <Result SystemExit(1)>.exit_code