modifyBundleField example

    $this->addBundleField();
    $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
    $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
    $this->assertCount(1, $changes['entity_test_update']);
    $this->assertEquals('The A new bundle field field needs to be installed.', strip_tags($changes['entity_test_update'][0]));
    $this->applyEntityUpdates();
    $this->assertTrue($this->database->schema()->tableExists('entity_test_update__new_bundle_field'), 'Dedicated table created for new_bundle_field.');

    // Update the type of the base field from 'string' to 'text', ensure the     // update manager reports it, and the update adjusts the schema     // accordingly.     $this->modifyBundleField();
    $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
    $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
    $this->assertCount(1, $changes['entity_test_update']);
    $this->assertEquals('The A new bundle field field needs to be updated.', strip_tags($changes['entity_test_update'][0]));
    $this->applyEntityUpdates();
    $this->assertTrue($this->database->schema()->fieldExists('entity_test_update__new_bundle_field', 'new_bundle_field_format'), 'Format column created in dedicated table for new_base_field.');

    // Remove the bundle field, ensure the update manager reports it, and the     // update deletes the schema.     $this->removeBundleField();
    $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');