12 files declare their use of MigrateTestCase

ActionTest.php in core/modules/action/tests/src/Unit/Plugin/migrate/source/ActionTest.php
Drupal6SqlBaseTest.php in core/modules/migrate_drupal/tests/src/Unit/source/d6/Drupal6SqlBaseTest.php
Contains \Drupal\Tests\migrate_drupal\Unit\source\d6\Drupal6SqlBaseTest.
DrupalSqlBaseTest.php in core/modules/migrate_drupal/tests/src/Unit/source/DrupalSqlBaseTest.php
FieldInstanceSettingsTest.php in core/modules/field/tests/src/Unit/Plugin/migrate/process/d7/FieldInstanceSettingsTest.php
FieldSettingsTest.php in core/modules/field/tests/src/Unit/Plugin/migrate/process/d7/FieldSettingsTest.php
FileUriTest.php in core/modules/file/tests/src/Unit/Plugin/migrate/process/d6/FileUriTest.php
FilterSettingsTest.php in core/modules/filter/tests/src/Kernel/Plugin/migrate/process/FilterSettingsTest.php
MigrateProcessTestCase.php in core/modules/migrate/tests/src/Unit/process/MigrateProcessTestCase.php
PerComponentEntityDisplayTest.php in core/modules/migrate/tests/src/Unit/destination/PerComponentEntityDisplayTest.php
Contains \Drupal\Tests\migrate\Unit\destination\PerComponentEntityDisplayTest.
PerComponentEntityFormDisplayTest.php in core/modules/migrate/tests/src/Unit/destination/PerComponentEntityFormDisplayTest.php
Contains \Drupal\Tests\migrate\Unit\destination\PerComponentEntityFormDisplayTest.
ProcessFieldTest.php in core/modules/field/tests/src/Unit/Plugin/migrate/process/ProcessFieldTest.php
UrlEncodeTest.php in core/modules/migrate/tests/src/Unit/process/UrlEncodeTest.php

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