--- /dev/null
+<?php
+
+namespace Drupal\Tests\Component\Discovery;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\Component\Discovery\YamlDiscovery;
+use org\bovigo\vfs\vfsStream;
+use org\bovigo\vfs\vfsStreamWrapper;
+use org\bovigo\vfs\vfsStreamDirectory;
+
+/**
+ * YamlDiscovery component unit tests.
+ *
+ * @group Discovery
+ */
+class YamlDiscoveryTest extends UnitTestCase {
+
+ /**
+ * Tests the YAML file discovery.
+ */
+ public function testDiscovery() {
+ vfsStreamWrapper::register();
+ $root = new vfsStreamDirectory('modules');
+ vfsStreamWrapper::setRoot($root);
+ $url = vfsStream::url('modules');
+
+ mkdir($url . '/test_1');
+ file_put_contents($url . '/test_1/test_1.test.yml', 'name: test');
+ file_put_contents($url . '/test_1/test_2.test.yml', 'name: test');
+
+ mkdir($url . '/test_2');
+ file_put_contents($url . '/test_2/test_3.test.yml', 'name: test');
+ // Write an empty YAML file.
+ file_put_contents($url . '/test_2/test_4.test.yml', '');
+
+ // Set up the directories to search.
+ $directories = [
+ 'test_1' => $url . '/test_1',
+ 'test_2' => $url . '/test_1',
+ 'test_3' => $url . '/test_2',
+ 'test_4' => $url . '/test_2',
+ ];
+
+ $discovery = new YamlDiscovery('test', $directories);
+ $data = $discovery->findAll();
+
+ $this->assertEquals(count($data), count($directories));
+ $this->assertArrayHasKey('test_1', $data);
+ $this->assertArrayHasKey('test_2', $data);
+ $this->assertArrayHasKey('test_3', $data);
+ $this->assertArrayHasKey('test_4', $data);
+
+ foreach (['test_1', 'test_2', 'test_3'] as $key) {
+ $this->assertArrayHasKey('name', $data[$key]);
+ $this->assertEquals($data[$key]['name'], 'test');
+ }
+
+ $this->assertSame([], $data['test_4']);
+ }
+
+}