refs #5820 added new test to make sure the report always uses default metrics by default

tests/PHPUnit/Core/Plugin/ReportTest.php

+<?php
+/**
+ * Piwik - free/libre analytics platform
+ *
+ * @link http://piwik.org
+ * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
+ */
+
+use Piwik\Plugin\Report;
+use Piwik\Plugins\ExamplePlugin\Reports\GetExampleReport;
+use Piwik\Metrics;
+
+/**
+ * @group Core
+ */
+class Plugin_ReportTest extends PHPUnit_Framework_TestCase
+{
+    /**
+     * @var Report
+     */
+    private $report;
+
+    public function setUp()
+    {
+        $this->report = new GetExampleReport();
+    }
+
+    public function test_reportShouldUseDefaultMetrics()
+    {
+        $this->assertEquals(Metrics::getDefaultMetrics(), $this->report->getMetrics());
+    }
+
+    public function test_reportShouldUseDefaultProcessedMetrics()
+    {
+        $this->assertEquals(Metrics::getDefaultProcessedMetrics(), $this->report->getProcessedMetrics());
+    }
+}
\ No newline at end of file