diff --git a/page_manager.module b/page_manager.module
index 7fd5c95..e5a8883 100644
--- a/page_manager.module
+++ b/page_manager.module
@@ -26,7 +26,7 @@ function page_manager_form_page_manager_display_variant_form_alter(array &$form,
 }
 
 /**
- * @todo.
+ * Saves the third party settings for a page display variant.
  *
  * @see page_manager_form_page_manager_display_variant_form_alter()
  */
diff --git a/src/EventSubscriber/DisableBlocksDisplayVariantSubscriber.php b/src/EventSubscriber/DisableBlocksDisplayVariantSubscriber.php
index 9471a2d..8536cd1 100644
--- a/src/EventSubscriber/DisableBlocksDisplayVariantSubscriber.php
+++ b/src/EventSubscriber/DisableBlocksDisplayVariantSubscriber.php
@@ -12,7 +12,7 @@
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
 /**
- * @todo.
+ * Disables page-level blocks for variants that select that option.
  */
 class DisableBlocksDisplayVariantSubscriber implements EventSubscriberInterface {
 
diff --git a/tests/src/Unit/DisableBlocksDisplayVariantSubscriberTest.php b/tests/src/Unit/DisableBlocksDisplayVariantSubscriberTest.php
new file mode 100644
index 0000000..4ef9a7b
--- /dev/null
+++ b/tests/src/Unit/DisableBlocksDisplayVariantSubscriberTest.php
@@ -0,0 +1,115 @@
+<?php
+
+/**
+ * @file
+ * Contains
+ *   \Drupal\Tests\page_manager\Unit\DisableBlocksDisplayVariantSubscriberTest.
+ */
+
+namespace Drupal\Tests\page_manager\Unit;
+
+use Drupal\Core\Render\PageDisplayVariantSelectionEvent;
+use Drupal\Core\Routing\RouteMatch;
+use Drupal\page_manager\EventSubscriber\DisableBlocksDisplayVariantSubscriber;
+use Drupal\Tests\UnitTestCase;
+use Symfony\Component\Routing\Route;
+
+/**
+ * @coversDefaultClass \Drupal\page_manager\EventSubscriber\DisableBlocksDisplayVariantSubscriber
+ *
+ * @group PageManager
+ */
+class DisableBlocksDisplayVariantSubscriberTest extends UnitTestCase {
+
+  /**
+   * @covers ::onSelectPageDisplayVariant
+   */
+  public function testNoRouteSlug() {
+    $page = $this->getMock('\Drupal\page_manager\PageInterface');
+    $page->expects($this->never())
+      ->method('getExecutable');
+    $route_match = new RouteMatch('the_route_name', new Route('/the/path/has/no/page_manager_page'), ['page_manager_page' => $page]);
+    $event = new PageDisplayVariantSelectionEvent('not_overridden', $route_match);
+    $subscriber = new DisableBlocksDisplayVariantSubscriber();
+    $subscriber->onSelectPageDisplayVariant($event);
+    $this->assertSame('not_overridden', $event->getPluginId());
+  }
+
+  /**
+   * @covers ::onSelectPageDisplayVariant
+   */
+  public function testNoSelectedVariant() {
+    $executable = $this->getMock('\Drupal\page_manager\PageExecutableInterface');
+    $page = $this->getMock('\Drupal\page_manager\PageInterface');
+    $page->expects($this->once())
+      ->method('getExecutable')
+      ->willReturn($executable);
+    $page->expects($this->never())
+      ->method('getThirdPartySetting');
+    $executable->expects($this->once())
+      ->method('selectDisplayVariant')
+      ->willReturn(NULL);
+    $route_match = new RouteMatch('the_route_name', new Route('/the/path/has/a/{page_manager_page}'), ['page_manager_page' => $page]);
+    $event = new PageDisplayVariantSelectionEvent('not_overridden', $route_match);
+
+    (new DisableBlocksDisplayVariantSubscriber())->onSelectPageDisplayVariant($event);
+    $this->assertSame('not_overridden', $event->getPluginId());
+  }
+
+  /**
+   * @covers ::onSelectPageDisplayVariant
+   *
+   * @dataProvider providerNoBlocksSettings
+   */
+  public function testNoBlocksSettings($settings, $expected) {
+    $executable = $this->getMock('\Drupal\page_manager\PageExecutableInterface');
+    $page = $this->getMock('\Drupal\page_manager\PageInterface');
+    $page->expects($this->once())
+      ->method('getExecutable')
+      ->willReturn($executable);
+    $page->expects($this->once())
+      ->method('getThirdPartySetting')
+      ->with('page_manager', 'the_plugin_id')
+      ->willReturn($settings);
+
+    $variant = $this->getMock('\Drupal\Core\Display\VariantInterface');
+    $variant->expects($this->once())
+      ->method('getPluginId')
+      ->willReturn('the_plugin_id');
+    $executable->expects($this->once())
+      ->method('selectDisplayVariant')
+      ->willReturn($variant);
+
+    $route_match = new RouteMatch('the_route_name', new Route('/the/path/has/a/{page_manager_page}'), ['page_manager_page' => $page]);
+    $event = new PageDisplayVariantSelectionEvent('not_overridden', $route_match);
+
+    (new DisableBlocksDisplayVariantSubscriber())->onSelectPageDisplayVariant($event);
+    $this->assertSame($expected, $event->getPluginId());
+  }
+
+  public function providerNoBlocksSettings() {
+    $data = [];
+    $data[] = [
+      NULL,
+      'not_overridden',
+    ];
+    $data[] = [
+      [],
+      'not_overridden',
+    ];
+    $data[] = [
+      ['no_blocks' => NULL],
+      'not_overridden',
+    ];
+    $data[] = [
+      ['no_blocks' => FALSE],
+      'not_overridden',
+    ];
+    $data[] = [
+      ['no_blocks' => TRUE],
+      'simple_page',
+    ];
+    return $data;
+  }
+
+}