diff --git a/core/modules/system/tests/src/Unit/Batch/BatchBuilderTest.php b/core/modules/system/tests/src/Unit/Batch/BatchBuilderTest.php
new file mode 100644
index 0000000..0a6816a
--- /dev/null
+++ b/core/modules/system/tests/src/Unit/Batch/BatchBuilderTest.php
@@ -0,0 +1,246 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\system\Unit\Batch\BatchBuilderTest.
+ */
+
+namespace Drupal\Tests\system\Unit\Batch;
+
+use Drupal\Core\Batch\BatchBuilder;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests for the batch builder class.
+ *
+ * @coversDefaultClass \Drupal\Core\Batch\BatchBuilder
+ *
+ * @group system
+ */
+class BatchBuilderTest extends UnitTestCase {
+
+  /**
+   * Tests the default values.
+   *
+   * @covers ::toArray
+   */
+  public function testSensibleDefaultValues() {
+    $batch = (new BatchBuilder())->toArray();
+
+    $this->assertTrue(is_array($batch), 'Batch builder create an array.');
+    $this->assertTrue(is_array($batch['operations']), 'Operations array exists.');
+    $this->assertEmpty($batch['operations'], 'Operations array is empty.');
+    $this->assertEquals('Processing', $batch['title'], 'Default title has been set.');
+    $this->assertEquals('Initializing.', $batch['init_message'], 'Default initialization message has been set.');
+    $this->assertEquals('Completed @current of @total.', $batch['progress_message'], 'Default progess message has been set.');
+    $this->assertEquals('An error has occurred.', $batch['error_message'], 'Default error message has been set.');
+    $this->assertNull($batch['finished'], 'Finished callback has not been set.');
+    $this->assertNull($batch['file'], 'No file is to be included.');
+    $this->assertTrue(is_array($batch['library']), 'Library array exists.');
+    $this->assertEmpty($batch['library'], 'No libraries have been added.');
+    $this->assertTrue(is_array($batch['url_options']), 'URL options array exists.');
+    $this->assertEmpty($batch['url_options'], 'URL options array is empty.');
+    $this->assertTrue($batch['progressive'], 'Progressive has been set.');
+    $this->assertFalse(isset($batch['queue']), 'Queue has not been set.');
+  }
+
+  /**
+   * Tests setTitle().
+   *
+   * @covers ::setTitle
+   */
+  public function testSetTitle() {
+    $batch = (new BatchBuilder())
+      ->setTitle('New Title')
+      ->toArray();
+
+    $this->assertEquals('New Title', $batch['title'], 'Title has been set.');
+  }
+
+  /**
+   * Tests setFinishCallback().
+   *
+   * @covers ::setFinishCallback
+   */
+  public function testSetFinishCallback() {
+    $batch = (new BatchBuilder())
+      ->setFinishCallback('\Drupal\Tests\system\Unit\Batch\BatchBuilderTest::finishedCallback')
+      ->toArray();
+
+    $this->assertEquals('\Drupal\Tests\system\Unit\Batch\BatchBuilderTest::finishedCallback', $batch['finished'], 'Finish callback has been set');
+  }
+
+  /**
+   * Tests setInitMessage().
+   *
+   * @covers ::setInitMessage
+   */
+  public function testSetInitMessage() {
+    $batch = (new BatchBuilder())
+      ->setInitMessage('New initialization message.')
+      ->toArray();
+
+    $this->assertEquals('New initialization message.', $batch['init_message'], 'Initialization message has been set/');
+  }
+
+  /**
+   * Tests setProgressMessage().
+   *
+   * @covers ::setProgressMessage
+   */
+  public function testSetProgressMessage() {
+    $batch = (new BatchBuilder())
+      ->setProgressMessage('Batch in progress...')
+      ->toArray();
+
+    $this->assertEquals('Batch in progress...', $batch['progress_message'], 'Progress message has been set.');
+  }
+
+  /**
+   * Tests setErrorMessage().
+   */
+  public function testSetErrorMessage() {
+    $batch = (new BatchBuilder())
+      ->setErrorMessage('Ooops. An error has occurred :(')
+      ->toArray();
+
+    $this->assertEquals('Ooops. An error has occurred :(', $batch['error_message'], 'Error message has been set.');
+  }
+
+  /**
+   * Tests setFile().
+   *
+   * @covers ::setFile
+   */
+  public function testSetFile() {
+    $batch = (new BatchBuilder())
+      ->setFile('filename.php')
+      ->toArray();
+
+    $this->assertEquals('filename.php', $batch['file'], 'The file has been set.');
+  }
+
+  /**
+   * Tests setting and adding libraries.
+   *
+   * @covers ::setLibraries
+   * @covers ::addLibraries
+   */
+  public function testAddingLibraries() {
+    $batch_builder = new BatchBuilder();
+    $batch = $batch_builder
+      ->addLibraries('library1')
+      ->toArray();
+
+    $this->assertEquals(1, count($batch['library']), 'Library added as string.');
+
+    $batch = $batch_builder
+      ->addLibraries(['library2', 'library3'])
+      ->toArray();
+
+    $this->assertEquals(3, count($batch['library']), 'Libraries added in an array.');
+
+    $batch = $batch_builder
+      ->setLibraries(['onlylibrary'])
+      ->toArray();
+
+    $this->assertEquals(1, count($batch['library']), 'Libraries replaced by an array.');
+  }
+
+  /**
+   * Tests setProgressive().
+   *
+   * @covers ::setProgressive
+   */
+  public function testSetProgressive() {
+    $batch_builder = new BatchBuilder();
+    $batch = $batch_builder
+      ->setProgressive(FALSE)
+      ->toArray();
+
+    $this->assertFalse($batch['progressive'], 'Batch has been set to not progressive.');
+
+    $batch = $batch_builder
+      ->setProgressive(TRUE)
+      ->toArray();
+
+    $this->assertTrue($batch['progressive'], 'Batch has been set to progressive.');
+  }
+
+  /**
+   * Tests setQueue().
+   *
+   * @covers ::setQueue
+   */
+  public function testSetQueue() {
+    $batch = (new BatchBuilder())
+      ->setQueue('BatchName', '\Drupal\Core\Queue\Batch')
+      ->toArray();
+
+    $this->assertArrayEquals([
+      'name' => 'BatchName',
+      'class' => '\Drupal\Core\Queue\Batch',
+    ], $batch['queue'], 'Batch queue has been set.');
+  }
+
+  /**
+   * Tests setUrlOptions().
+   *
+   * @covers ::setUrlOptions
+   */
+  public function testSetUrlOptions() {
+    $options = [
+      'absolute' => TRUE,
+      'language' => 'de',
+    ];
+    $batch = (new BatchBuilder())
+      ->setUrlOptions($options)
+      ->toArray();
+
+    $this->assertEquals($options, $batch['url_options'], 'URL options have been set.');
+  }
+
+  /**
+   * Tests addOperation().
+   *
+   * @covers ::addOperation
+   */
+  public function testAddOperation() {
+    $batch_builder = new BatchBuilder();
+    $batch = $batch_builder
+      ->addOperation('\Drupal\Tests\system\Unit\Batch\BatchBuilderTest::operationCallback')
+      ->toArray();
+
+    $this->assertEquals(1, count($batch['operations']), 'One operation has been added.');
+
+    $batch = $batch_builder
+      ->addOperation('\Drupal\Tests\system\Unit\Batch\BatchBuilderTest::operationCallback', [2])
+      ->addOperation('\Drupal\Tests\system\Unit\Batch\BatchBuilderTest::operationCallback', [3])
+      ->toArray();
+
+    $this->assertEquals(3, count($batch['operations']), 'Three operations have been added.');
+
+    $this->assertEquals('\Drupal\Tests\system\Unit\Batch\BatchBuilderTest::operationCallback', $batch['operations'][0][0], 'Operation callback has been set.');
+    $this->assertEquals([], $batch['operations'][0][1], 'First operation parameters set correctly.');
+    $this->assertEquals([2], $batch['operations'][1][1], 'Second operation parameters set correctly.');
+    $this->assertEquals([3], $batch['operations'][2][1], 'Third operation parameters set correctly.');
+
+  }
+
+  /**
+   * Empty callback for the tests.
+   *
+   * @internal
+   */
+  public static function finishedCallback() {
+  }
+
+  /**
+   * Empty callback for the tests.
+   *
+   * @internal
+   */
+  public static function operationCallback() {
+  }
+
+}