Improve the CBT_Theme_Fonts class tests

[matiasbenedetto]

What?

Simplify the CBT_Theme_Fonts class tests.

• Try to make the tests more granular and simple.
• Make the tests follow core guidelines.
• Avoid manual operations to manipulate or create themes inside the test cases. Example:
  

  create-block-theme/tests/test-theme-fonts.php

  Lines 27 to 41 in 128d363

  	wp_set_current_user( self::$admin_id );
  	$user_data_begin = CBT_Theme_JSON_Resolver::get_user_data()->get_settings();
  	$test_theme_slug = $this->create_blank_theme();
  	$this->activate_user_font();
  	$user_data_before = CBT_Theme_JSON_Resolver::get_user_data()->get_settings();
  	$theme_data_before = CBT_Theme_JSON_Resolver::get_theme_data()->get_settings();
  	$this->save_theme();
  	$user_data_after = CBT_Theme_JSON_Resolver::get_user_data()->get_settings();
  	$theme_data_after = CBT_Theme_JSON_Resolver::get_theme_data()->get_settings();

Why?

• Make the tests more effective for testing the class methods.
• Make the tests easier to understand, maintain, and update.