20 files declare their use of FieldKernelTestBase in Drupal 9

BooleanItemTest.php in core/modules/field/tests/src/Kernel/Boolean/BooleanItemTest.php

CommentItemTest.php in core/modules/comment/tests/src/Kernel/CommentItemTest.php

DateRangeItemTest.php in core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php

DateTimeItemTest.php in core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php

EmailItemTest.php in core/modules/field/tests/src/Kernel/Email/EmailItemTest.php

EntityReferenceItemTest.php in core/modules/field/tests/src/Kernel/EntityReference/EntityReferenceItemTest.php

FieldRdfaTestBase.php in core/modules/rdf/tests/src/Kernel/Field/FieldRdfaTestBase.php

FileItemTest.php in core/modules/file/tests/src/Kernel/FileItemTest.php

ImageFormatterTest.php in core/modules/image/tests/src/Kernel/ImageFormatterTest.php

ImageItemTest.php in core/modules/image/tests/src/Kernel/ImageItemTest.php

LinkItemSerializationTest.php in core/modules/link/tests/src/Kernel/LinkItemSerializationTest.php

LinkItemTest.php in core/modules/link/tests/src/Kernel/LinkItemTest.php

LinkItemUrlValidationTest.php in core/modules/link/tests/src/Kernel/LinkItemUrlValidationTest.php

NumberItemTest.php in core/modules/field/tests/src/Kernel/Number/NumberItemTest.php

OptionsFieldUnitTestBase.php in core/modules/options/tests/src/Kernel/OptionsFieldUnitTestBase.php

TelephoneItemTest.php in core/modules/telephone/tests/src/Kernel/TelephoneItemTest.php

TextWithSummaryItemTest.php in core/modules/text/tests/src/Kernel/TextWithSummaryItemTest.php

TimestampItemTest.php in core/modules/field/tests/src/Kernel/Timestamp/TimestampItemTest.php

UriItemTest.php in core/modules/field/tests/src/Kernel/Uri/UriItemTest.php

UuidItemTest.php in core/modules/field/tests/src/Kernel/String/UuidItemTest.php