10 files declare their use of FeedsBrowserTestBase in Feeds 8.3

CsvParserFeedFormTest.php in tests/src/Functional/Feeds/Parser/Form/CsvParserFeedFormTest.php

DeleteFeedTest.php in tests/src/Functional/Plugin/Action/DeleteFeedTest.php

FeedsDrushCommandsTest.php in tests/src/Functional/Commands/FeedsDrushCommandsTest.php

FeedsItemFormatterTestBase.php in tests/src/Functional/Plugin/Field/FieldFormatter/FeedsItemFormatterTestBase.php

FileTest.php in tests/src/Functional/Feeds/Target/FileTest.php

HttpFetcherTest.php in tests/src/Functional/Feeds/Fetcher/HttpFetcherTest.php

ItemListControllerTest.php in tests/src/Functional/Controller/ItemListControllerTest.php

MappingFormTest.php in tests/src/Functional/Form/MappingFormTest.php

PasswordTest.php in tests/src/Functional/Feeds/Target/PasswordTest.php

UploadFetcherTest.php in tests/src/Functional/Feeds/Fetcher/UploadFetcherTest.php