.../Drupal/Tests/Core/Cache/CacheContextsTest.php  | 95 ++++++++++++++++------
 1 file changed, 72 insertions(+), 23 deletions(-)

diff --git a/core/tests/Drupal/Tests/Core/Cache/CacheContextsTest.php b/core/tests/Drupal/Tests/Core/Cache/CacheContextsTest.php
index fff9df2..87b7798 100644
--- a/core/tests/Drupal/Tests/Core/Cache/CacheContextsTest.php
+++ b/core/tests/Drupal/Tests/Core/Cache/CacheContextsTest.php
@@ -9,7 +9,9 @@
 
 use Drupal\Core\Cache\CacheContexts;
 use Drupal\Core\Cache\CacheContextInterface;
+use Drupal\Core\Cache\CalculatedCacheContextInterface;
 use Drupal\Tests\UnitTestCase;
+use Symfony\Component\DependencyInjection\Container;
 
 /**
  * @coversDefaultClass \Drupal\Core\Cache\CacheContexts
@@ -17,20 +19,19 @@
  */
 class CacheContextsTest extends UnitTestCase {
 
-  public function testContextPlaceholdersAreReplaced() {
+  /**
+   * @covers ::convertTokensToKeys
+   */
+  public function testConvertTokensToKeys() {
     $container = $this->getMockContainer();
-    $container->expects($this->once())
-              ->method("get")
-              ->with("cache_context.foo")
-              ->will($this->returnValue(new FooCacheContext()));
-
     $cache_contexts = new CacheContexts($container, $this->getContextsFixture());
 
-    $new_keys = $cache_contexts->convertTokensToKeys(
-      ['foo']
-    );
+    $new_keys = $cache_contexts->convertTokensToKeys([
+      'foo',
+      'baz:parameter',
+    ]);
 
-    $expected = ['bar'];
+    $expected = ['bar', 'baz.cnenzrgre'];
     $this->assertEquals($expected, $new_keys);
   }
 
@@ -44,24 +45,41 @@ public function testInvalidContext() {
     $container = $this->getMockContainer();
     $cache_contexts = new CacheContexts($container, $this->getContextsFixture());
 
-    $cache_contexts->convertTokensToKeys(
-      ["non-cache-context"]
-    );
+    $cache_contexts->convertTokensToKeys(["non-cache-context"]);
+  }
+
+  /**
+   * @covers ::convertTokensToKeys
+   *
+   * @expectedException \Exception
+   *
+   * @dataProvider providerTestInvalidCalculatedContext
+   */
+  public function testInvalidCalculatedContext($context_token) {
+    $container = $this->getMockContainer();
+    $cache_contexts = new CacheContexts($container, $this->getContextsFixture());
+
+    $cache_contexts->convertTokensToKeys([$context_token]);
+  }
+
+  /**
+   * Provides a list of invalid 'baz' cache contexts: the parameter is missing.
+   */
+  public function providerTestInvalidCalculatedContext() {
+    return [
+      ['baz'],
+      ['baz:'],
+    ];
   }
 
   public function testAvailableContextStrings() {
     $cache_contexts = new CacheContexts($this->getMockContainer(), $this->getContextsFixture());
     $contexts = $cache_contexts->getAll();
-    $this->assertEquals(array("foo"), $contexts);
+    $this->assertEquals(array("foo", "baz"), $contexts);
   }
 
   public function testAvailableContextLabels() {
     $container = $this->getMockContainer();
-    $container->expects($this->once())
-              ->method("get")
-              ->with("cache_context.foo")
-              ->will($this->returnValue(new FooCacheContext()));
-
     $cache_contexts = new CacheContexts($container, $this->getContextsFixture());
     $labels = $cache_contexts->getLabels();
     $expected = array("foo" => "Foo");
@@ -69,14 +87,22 @@ public function testAvailableContextLabels() {
   }
 
   protected function getContextsFixture() {
-    return array('foo');
+    return array('foo', 'baz');
   }
 
   protected function getMockContainer() {
-    return $this->getMockBuilder('Drupal\Core\DependencyInjection\Container')
-                ->disableOriginalConstructor()
-                ->getMock();
+    $container = $this->getMockBuilder('Drupal\Core\DependencyInjection\Container')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $container->expects($this->any())
+      ->method('get')
+      ->will($this->returnValueMap([
+        ['cache_context.foo', Container::EXCEPTION_ON_INVALID_REFERENCE, new FooCacheContext()],
+        ['cache_context.baz', Container::EXCEPTION_ON_INVALID_REFERENCE, new BazCacheContext()],
+      ]));
+    return $container;
   }
+
 }
 
 /**
@@ -100,3 +126,26 @@ public function getContext() {
 
 }
 
+/**
+ * Fake calculated cache context class.
+ */
+class BazCacheContext implements CalculatedCacheContextInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getLabel() {
+    return 'Baz';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getContext($parameter) {
+    if (!is_string($parameter) || strlen($parameter) ===  0) {
+      throw new \Exception;
+    }
+    return 'baz.' . str_rot13($parameter);
+  }
+
+}