def METHOD_NAME(package_command, first_app):
    """A debian app can be packaged."""
    # Set the packaging format
    first_app.packaging_format = "deb"
    # Mock the actual packaging call
    package_command._package_deb = mock.MagicMock()
    # Package the app
    package_command.package_app(first_app)
    # Assert the right backend was called.
    package_command._package_deb.assert_called_once_with(first_app)