You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: backend_common_tests.rb
    path of file: ./repos/classifier-reborn/test/backends
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module BackendCommonTests
  def test_initial_values
    assert @backend.total_words.zero?
    assert @backend.total_trainings.zero?
    assert @backend.category_keys.empty?
  e
    
  def test_category_training
    refute @backend.category_has_trainings?(:Interesting)
    @backend.update_category_training_count(:Interesting, 10)
    assert @backend.category_has_trainings?(:Interesting)
    assert_equal 10, @backend.category_training_count(:Interesting)
    @backend.update_category_training_count(:Interesting, -7)
    assert_equal 3, @backend.category_training_count(:Interesting)
  end