17 files declare their use of CronRunTrait in Drupal 8

AggregatorCronTest.php in core/modules/aggregator/tests/src/Functional/AggregatorCronTest.php

BrowserTestBaseTest.php in core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php

CronRunTest.php in core/modules/system/tests/src/Functional/System/CronRunTest.php

FeedLanguageTest.php in core/modules/aggregator/tests/src/Functional/FeedLanguageTest.php

FieldUpdateTest.php in core/modules/field/tests/src/Functional/Update/FieldUpdateTest.php

HelpTopicSearchTest.php in core/modules/help_topics/tests/src/Functional/HelpTopicSearchTest.php

LocaleUpdateCronTest.php in core/modules/locale/tests/src/Functional/LocaleUpdateCronTest.php

ReEnableModuleFieldTest.php in core/modules/field/tests/src/Functional/ReEnableModuleFieldTest.php

SearchCommentTest.php in core/modules/search/tests/src/Functional/SearchCommentTest.php

SearchIntegrationTest.php in core/modules/views/tests/src/Functional/SearchIntegrationTest.php

SearchMultilingualTest.php in core/modules/views/tests/src/Functional/SearchMultilingualTest.php

SearchNumberMatchingTest.php in core/modules/search/tests/src/Functional/SearchNumberMatchingTest.php

SearchNumbersTest.php in core/modules/search/tests/src/Functional/SearchNumbersTest.php

SearchRankingTest.php in core/modules/search/tests/src/Functional/SearchRankingTest.php

StatisticsAdminTest.php in core/modules/statistics/tests/src/Functional/StatisticsAdminTest.php

UpdateCoreTest.php in core/modules/update/tests/src/Functional/UpdateCoreTest.php

WebTestBase.php in core/modules/simpletest/src/WebTestBase.php