diff --git a/core/lib/Drupal/Core/Breadcrumb/BreadcrumbManager.php b/core/lib/Drupal/Core/Breadcrumb/BreadcrumbManager.php
index 45de662bfb5..9e6f9b7ee90 100644
--- a/core/lib/Drupal/Core/Breadcrumb/BreadcrumbManager.php
+++ b/core/lib/Drupal/Core/Breadcrumb/BreadcrumbManager.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Breadcrumb;
 
+use Drupal\Component\Utility\String;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 
 /**
@@ -85,7 +86,7 @@ class BreadcrumbManager implements BreadcrumbBuilderInterface {
         break;
       }
       else {
-        throw new \UnexpectedValueException(format_string('Invalid breadcrumb returned by !class::build().', array('!class' => get_class($builder))));
+        throw new \UnexpectedValueException(String::format('Invalid breadcrumb returned by !class::build().', array('!class' => get_class($builder))));
       }
     }
     // Allow modules to alter the breadcrumb.
diff --git a/core/tests/Drupal/Tests/Core/Breadcrumb/BreadcrumbManagerTest.php b/core/tests/Drupal/Tests/Core/Breadcrumb/BreadcrumbManagerTest.php
new file mode 100644
index 00000000000..f3ac82abe29
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Breadcrumb/BreadcrumbManagerTest.php
@@ -0,0 +1,157 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Core\Breadcrumb\BreadcrumbManagerTest.
+ */
+
+namespace Drupal\Tests\Core\Breadcrumb;
+
+use Drupal\Core\Breadcrumb\BreadcrumbManager;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests the breadcrumb manager.
+ *
+ * @group Drupal
+ * @group Breadcrumb
+ *
+ * @covers \Drupal\Tests\Core\Breadcrumb\BreadcrumbManagerTest
+ */
+class BreadcrumbManagerTest extends UnitTestCase {
+
+  /**
+   * The tested breadcrumb manager.
+   *
+   * @var \Drupal\Core\Breadcrumb\BreadcrumbManager
+   */
+  protected $breadcrumbManager;
+
+  /**
+   * The mocked module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $moduleHandler;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    $this->moduleHandler = $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface');
+    $this->breadcrumbManager = new BreadcrumbManager($this->moduleHandler);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Breadcrumb manager',
+      'description' => 'Tests the breadcrumb manager.',
+      'group' => 'Menu'
+    );
+  }
+
+  /**
+   * Tests the breadcrumb manager without any set breadcrumb.
+   */
+  public function testBuildWithoutBuilder() {
+    $result = $this->breadcrumbManager->build(array());
+    $this->assertEquals(array(), $result);
+  }
+
+  /**
+   * Tests the build method with a single breadcrumb builder.
+   */
+  public function testBuildWithSingleBuilder() {
+    $builder = $this->getMock('Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface');
+    $breadcrumb = array('<a href="/example">Test</a>');
+
+    $attributes = array('key' => 'value');
+
+    $builder->expects($this->once())
+      ->method('build')
+      ->will($this->returnValue($breadcrumb));
+
+    $this->moduleHandler->expects($this->once())
+      ->method('alter')
+      ->with('system_breadcrumb', $breadcrumb, $attributes, array('builder' => $builder));
+
+    $this->breadcrumbManager->addBuilder($builder, 0);
+
+    $result = $this->breadcrumbManager->build($attributes);
+    $this->assertEquals($breadcrumb, $result);
+  }
+
+  /**
+   * Tests multiple breadcrumb builder with different priority.
+   */
+  public function testBuildWithMultipleApplyingBuilders() {
+    $builder1 = $this->getMock('Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface');
+    $builder1->expects($this->never())
+      ->method('build');
+
+    $builder2 = $this->getMock('Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface');
+    $breadcrumb2 = array('<a href="/example2">Test2</a>');
+    $builder2->expects($this->once())
+      ->method('build')
+      ->will($this->returnValue($breadcrumb2));
+
+    $attributes = array('key' => 'value');
+
+    $this->moduleHandler->expects($this->once())
+      ->method('alter')
+      ->with('system_breadcrumb', $breadcrumb2, $attributes, array('builder' => $builder2));
+
+    $this->breadcrumbManager->addBuilder($builder1, 0);
+    $this->breadcrumbManager->addBuilder($builder2, 10);
+
+    $result = $this->breadcrumbManager->build($attributes);
+    $this->assertEquals($breadcrumb2, $result);
+  }
+
+  /**
+   * Tests multiple breadcrumb builders of which one returns NULL.
+   */
+  public function testBuildWithOneNotApplyingBuilders() {
+    $builder1 = $this->getMock('Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface');
+    $builder1->expects($this->once())
+      ->method('build')
+      ->will($this->returnValue(NULL));
+
+    $builder2 = $this->getMock('Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface');
+    $breadcrumb2 = array('<a href="/example2">Test2</a>');
+    $builder2->expects($this->once())
+      ->method('build')
+      ->will($this->returnValue($breadcrumb2));
+
+    $attributes = array('key' => 'value');
+
+    $this->moduleHandler->expects($this->once())
+      ->method('alter')
+      ->with('system_breadcrumb', $breadcrumb2, $attributes, array('builder' => $builder2));
+
+    $this->breadcrumbManager->addBuilder($builder1, 10);
+    $this->breadcrumbManager->addBuilder($builder2, 0);
+
+    $result = $this->breadcrumbManager->build($attributes);
+    $this->assertEquals($breadcrumb2, $result);
+  }
+
+  /**
+   * Tests a breadcrumb builder with a bad return value.
+   *
+   * @expectedException \UnexpectedValueException
+   */
+  public function testBuildWithInvalidBreadcrumbResult() {
+    $builder = $this->getMock('Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface');
+    $builder->expects($this->once())
+      ->method('build')
+      ->will($this->returnValue('invalid_result'));
+
+    $this->breadcrumbManager->addBuilder($builder, 0);
+    $this->breadcrumbManager->build(array());
+  }
+
+}