7 files declare their use of Tasks

GenerateThemeTest.php in core/tests/Drupal/Tests/Core/Command/GenerateThemeTest.php
GenerateThemeTest.php in core/tests/Drupal/BuildTests/Command/GenerateThemeTest.php
HtRouterTest.php in core/tests/Drupal/BuildTests/Framework/Tests/HtRouterTest.php
QuickStartTest.php in core/tests/Drupal/Tests/Core/Command/QuickStartTest.php
RecipeQuickStartTest.php in core/tests/Drupal/Tests/Core/Recipe/RecipeQuickStartTest.php
Tasks.php in core/modules/system/tests/modules/database_statement_monitoring_test/src/sqlite/Install/Tasks.php
Tasks.php in core/lib/Drupal/Core/Database/Driver/sqlite/Install/Tasks.php

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