Activate bootstrap theme in BrowserTestBase phpunit test In a Drupal 8 testclass I am trying to install the bootstrap theme (v 8.x-3.1). It is saved in the /theme directory. No problem when using the UI. Unfortunately I get an error in the test when I try to install it with this code:

/*
 * Anytest
 * @group proreos
 * @runTestsInSeparateProcesses
 * @preserveGlobalState disabled
 *  
 */
class CalculatorControllerTest extends BrowserTestBase {

  public function setUp() {
    parent::setUp();
    \Drupal::service('theme_handler')-&gt;install(array('bootstrap'));
  }


The test exits with the following error:

PHPunit Test failed to complete; Error: PHPUnit 4.8.27 by Sebastian
Bergmann and contributors.
There was 1 error:

1)
Drupal\Tests\preosasde\Functional\CalculatorControllerTest::testCalculatorController
Drupal\Core\Config\Schema\SchemaIncompleteException: Schema errors for
bootstrap.settings with the following errors: bootstrap.settings:schemas
missing schema

/var/www/vhosts/proreos/core/lib/Drupal/Core/Config/Testing/ConfigSchemaChecker.php:93


Any advice on this? Anyone tried to install bootstrap in an PHPUnit test sucessfully?

Thanks!
Thanks to Berdir for the hint. The solution is to disable the schema validation here. It's done with this code in my testclass:

protected function getConfigSchemaExclusions() {
  return array_merge(parent::getConfigSchemaExclusions(), ['bootstrap.settings']);
}