Add Unit tests for getSelectCountSql

Author: osrecio

app/code/Magento/Reports/Model/ResourceModel/Review/Customer/Collection.php

@@ -106,7 +106,7 @@ protected function _joinCustomers()
      */
     public function getSelectCountSql()
     {
-        $countSelect = clone $this->_select;
+        $countSelect = clone $this->getSelect();
         $countSelect->reset(\Magento\Framework\DB\Select::ORDER);
         $countSelect->reset(\Magento\Framework\DB\Select::GROUP);
         $countSelect->reset(\Magento\Framework\DB\Select::HAVING);

app/code/Magento/Reports/Test/Unit/Model/ResourceModel/Report/Review/Customer/CollectionTest.php

@@ -0,0 +1,41 @@
+<?php
+/**
+ * CollectionTest
+ *
+ * @copyright Copyright (c) 2017 Interactiv4
+ * @author    [email protected]
+ */
+
+namespace Magento\Reports\Test\Unit\Model\ResourceModel\Review\Customer;
+
+use Magento\Framework\DB\Select;
+use Magento\Reports\Model\ResourceModel\Review\Customer\Collection;
+
+class CollectionTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @var \PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $selectMock;
+
+    protected function setUp()
+    {
+        $this->selectMock = $this->createMock(Select::class);
+    }
+
+    public function testGetSelectCountSql()
+    {
+        /** @var $collection \PHPUnit_Framework_MockObject_MockObject */
+        $collection = $this->getMockBuilder(Collection::class)
+            ->setMethods(['getSelect'])
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $collection->expects($this->atLeastOnce())->method('getSelect')->willReturn($this->selectMock);
+
+        $this->selectMock->expects($this->atLeastOnce())->method('reset')->willReturnSelf();
+        $this->selectMock->expects($this->exactly(1))->method('columns')->willReturnSelf();
+
+        $this->assertEquals($this->selectMock, $collection->getSelectCountSql());
+    }
+}