--- /dev/null
+<?php
+
+namespace Drupal\Tests\locale\Functional;
+
+use Drupal\Core\StreamWrapper\PublicStream;
+use Drupal\language\Entity\ConfigurableLanguage;
+use org\bovigo\vfs\vfsStream;
+
+/**
+ * Tests locale translation download.
+ *
+ * @group locale
+ */
+class LocaleTranslationDownloadTest extends LocaleUpdateBase {
+
+ /**
+ * The virtual file stream for storing translations.
+ *
+ * @var \org\bovigo\vfs\vfsStreamDirectory
+ */
+ protected $translationsStream;
+
+ /**
+ * {@inheritdoc}
+ */
+ protected function setUp() {
+ parent::setUp();
+ $moduleHandler = $this->container->get('module_handler');
+ $moduleHandler->loadInclude('locale', 'inc', 'locale.batch');
+ ConfigurableLanguage::createFromLangcode('de')->save();
+
+ // Let the translations:// stream wrapper point to a virtual file system to
+ // make it independent from the test environment.
+ $this->translationsStream = vfsStream::setup('translations');
+ \Drupal::configFactory()->getEditable('locale.settings')
+ ->set('translation.path', $this->translationsStream->url())
+ ->save();
+ }
+
+ /**
+ * Tests translation download from remote sources.
+ */
+ public function testUpdateImportSourceRemote() {
+
+ // Provide remote and 'previously' downloaded translation file.
+ $this->setTranslationFiles();
+ vfsStream::create([
+ 'contrib_module_one-8.x-1.1.de._po' => '__old_content__',
+ ], $this->translationsStream);
+
+ $url = \Drupal::service('url_generator')->generateFromRoute('<front>', [], ['absolute' => TRUE]);
+ $uri = $url . PublicStream::basePath() . '/remote/8.x/contrib_module_one/contrib_module_one-8.x-1.1.de._po';
+ $source_file = (object) [
+ 'uri' => $uri,
+ ];
+
+ $result = locale_translation_download_source($source_file, 'translations://');
+
+ $this->assertEquals('translations://contrib_module_one-8.x-1.1.de._po', $result->uri);
+ $this->assertFalse(file_exists('translations://contrib_module_one-8.x-1.1.de_0._po'));
+ $this->assertTrue(file_exists('translations://contrib_module_one-8.x-1.1.de._po'));
+ $this->assertNotContains('__old_content__', file_get_contents('translations://contrib_module_one-8.x-1.1.de._po'));
+ }
+
+}