async def test_get_valid_credentials_with_valid_existing_creds(
      self, manager, mock_tool_context
  ):
    """Test that valid existing credentials are returned immediately.

    When credentials are already valid, no refresh or OAuth flow
    should be needed. This is the optimal happy path scenario.
    """
    # Create mock credentials that are already valid
    mock_creds = Mock(spec=Credentials)
    mock_creds.valid = True
    manager.credentials_config.credentials = mock_creds

    result = await manager.get_valid_credentials(mock_tool_context)

    assert result == mock_creds
    # Verify no OAuth flow was triggered
    mock_tool_context.get_auth_response.assert_not_called()
    mock_tool_context.request_credential.assert_not_called()
Test that valid existing credentials are returned immediately.

    When credentials are already valid, no refresh or OAuth flow
    should be needed. This is the optimal happy path scenario.
    
tests/unittests/tools/bigquery/test_bigquery_credentials_manager.py