--- /dev/null
+<?php
+
+namespace Drupal\Tests\config_translation\Kernel;
+
+use Drupal\Core\Routing\RouteMatch;
+use Drupal\KernelTests\KernelTestBase;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Tests config mapper.
+ *
+ * @group config_translation
+ */
+class ConfigMapperTest extends KernelTestBase {
+
+ /**
+ * {@inheritdoc}
+ */
+ public static $modules = [
+ 'config_translation',
+ 'config_translation_test',
+ 'language',
+ 'locale',
+ 'system',
+ ];
+
+ /**
+ * Tests adding config names to mapper.
+ */
+ public function testAddingConfigNames() {
+ // Get a config names mapper.
+ $mappers = \Drupal::service('plugin.manager.config_translation.mapper')->getMappers();
+ $mapper = $mappers['system.site_information_settings'];
+
+ // Test that it doesn't contain a config name from config_translation_test.
+ $config_names = $mapper->getConfigNames();
+ $this->assertNotContains('config_translation_test.content', $config_names);
+
+ // Call populateFromRouteMatch() to dispatch the "config mapper populate"
+ // event.
+ $mapper->populateFromRouteMatch(new RouteMatch('test', new Route('/')));
+
+ // Test that it contains the new config name from config_translation_test.
+ $config_names = $mapper->getConfigNames();
+ $this->assertContains('config_translation_test.content', $config_names);
+ }
+
+}