preprocess-2.0.0/tests/themes/test_preprocess_theme/test_preprocess_theme.preprocessors.yml

test_preprocess_theme_image.preprocessor:
  class: \Drupal\test_preprocess_theme\Plugin\Preprocess\ThemePreprocessImageTestPlugin
  hook: image

test_preprocess_theme_node__article.preprocessor:
  class: \Drupal\test_preprocess_theme\Plugin\Preprocess\ThemePreprocessNodeArticleTestPlugin
  hook: node__article