Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/phpunit/php-code-coverage/tests/_files/CoverageNotPublicTest.php

@@ -0,0 +1,12 @@
+<?php
+class CoverageNotPublicTest extends PHPUnit_Framework_TestCase
+{
+    /**
+     * @covers CoveredClass::<!public>
+     */
+    public function testSomething()
+    {
+        $o = new CoveredClass;
+        $o->publicMethod();
+    }
+}