diff --git a/.travis.yml b/.travis.yml
index 95eb5ecb62bca..74e374412fff4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,7 +9,7 @@ addons:
     - postfix
 language: php
 php:
-  - 5.6
+  - 5.6.29
   - 7.0
 env:
   global:
diff --git a/app/code/Magento/Captcha/Test/Unit/Helper/DataTest.php b/app/code/Magento/Captcha/Test/Unit/Helper/DataTest.php
index 93379cff52f2c..40558b3cae8a5 100644
--- a/app/code/Magento/Captcha/Test/Unit/Helper/DataTest.php
+++ b/app/code/Magento/Captcha/Test/Unit/Helper/DataTest.php
@@ -53,10 +53,6 @@ protected function setUp()
      */
     public function testGetCaptcha()
     {
-        if (!function_exists("imageftbbox")) {
-            $this->markTestSkipped('imageftbbox is not available on the test environment');
-        }
-
         $this->configMock->expects(
             $this->once()
         )->method(
diff --git a/app/code/Magento/Captcha/Test/Unit/Model/DefaultTest.php b/app/code/Magento/Captcha/Test/Unit/Model/DefaultTest.php
index 26984af3df32c..649bce192614b 100644
--- a/app/code/Magento/Captcha/Test/Unit/Model/DefaultTest.php
+++ b/app/code/Magento/Captcha/Test/Unit/Model/DefaultTest.php
@@ -88,9 +88,6 @@ class DefaultTest extends \PHPUnit_Framework_TestCase
      */
     protected function setUp()
     {
-        if (!function_exists("imageftbbox")) {
-            $this->markTestSkipped('imageftbbox is not available on the test environment');
-        }
         $this->session = $this->_getSessionStub();
 
         $this->_storeManager = $this->getMock(
diff --git a/app/code/Magento/Catalog/Model/ProductLink/CollectionProvider.php b/app/code/Magento/Catalog/Model/ProductLink/CollectionProvider.php
index 917a47b637cea..eb4e385993ac2 100644
--- a/app/code/Magento/Catalog/Model/ProductLink/CollectionProvider.php
+++ b/app/code/Magento/Catalog/Model/ProductLink/CollectionProvider.php
@@ -48,9 +48,21 @@ public function getCollection(\Magento\Catalog\Model\Product $product, $type)
         $products = $this->providers[$type]->getLinkedProducts($product);
         $converter = $this->converterPool->getConverter($type);
         $output = [];
+        $sorterItems = [];
         foreach ($products as $item) {
             $output[$item->getId()] = $converter->convert($item);
         }
-        return $output;
+
+        foreach ($output as $item) {
+            $itemPosition = $item['position'];
+            if (!isset($sorterItems[$itemPosition])) {
+                $sorterItems[$itemPosition] = $item;
+            } else {
+                $newPosition = $itemPosition + 1;
+                $sorterItems[$newPosition] = $item;
+            }
+        }
+        ksort($sorterItems);
+        return $sorterItems;
     }
 }
diff --git a/app/code/Magento/Catalog/Test/Unit/Model/CollectionProviderTest.php b/app/code/Magento/Catalog/Test/Unit/Model/CollectionProviderTest.php
new file mode 100644
index 0000000000000..b543c92ac0875
--- /dev/null
+++ b/app/code/Magento/Catalog/Test/Unit/Model/CollectionProviderTest.php
@@ -0,0 +1,110 @@
+<?php
+/**
+ * Copyright © 2013-2017 Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Catalog\Test\Unit\Model;
+
+use Magento\Catalog\Model\ProductLink\CollectionProvider;
+use Magento\Catalog\Model\ProductLink\CollectionProviderInterface;
+use Magento\Catalog\Model\ProductLink\Converter\ConverterInterface;
+use Magento\Catalog\Model\ProductLink\Converter\ConverterPool;
+use Magento\Catalog\Model\Product;
+
+class CollectionProviderTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @var CollectionProvider
+     */
+    private $model;
+
+    /**
+     * @var \PHPUnit_Framework_MockObject_MockObject
+     */
+    private $converterPoolMock;
+
+    /**
+     * @var \PHPUnit_Framework_MockObject_MockObject
+     */
+    private $providerMock;
+
+    /**
+     * @var \PHPUnit_Framework_MockObject_MockObject
+     */
+    private $productMock;
+
+    /**
+     * @var \PHPUnit_Framework_MockObject_MockObject
+     */
+    private $converterMock;
+
+    protected function setUp()
+    {
+        $this->productMock = $this->getMock(Product::class, [], [], '', false, false);
+        $this->converterPoolMock = $this->getMock(ConverterPool::class, [], [], '', false, false);
+        $this->providerMock = $this->getMock(CollectionProviderInterface::class);
+        $this->converterMock = $this->getMock(ConverterInterface::class);
+
+        $this->model = new CollectionProvider($this->converterPoolMock, ['crosssell' => $this->providerMock]);
+    }
+
+    /**
+     * Test sort order of linked products based on configured item position.
+     */
+    public function testGetCollection()
+    {
+        $linkedProductOneMock = $this->getMock(Product::class, [], [], '', false, false);
+        $linkedProductTwoMock = $this->getMock(Product::class, [], [], '', false, false);
+        $linkedProductThreeMock = $this->getMock(Product::class, [], [], '', false, false);
+
+        $linkedProductOneMock->expects($this->once())->method('getId')->willReturn(1);
+        $linkedProductTwoMock->expects($this->once())->method('getId')->willReturn(2);
+        $linkedProductThreeMock->expects($this->once())->method('getId')->willReturn(3);
+
+        $this->converterPoolMock->expects($this->once())
+            ->method('getConverter')
+            ->with('crosssell')
+            ->willReturn($this->converterMock);
+
+        $map = [
+            [$linkedProductOneMock, ['name' => 'Product One', 'position' => 10]],
+            [$linkedProductTwoMock, ['name' => 'Product Two', 'position' => 2]],
+            [$linkedProductThreeMock, ['name' => 'Product Three', 'position' => 2]],
+        ];
+
+        $this->converterMock->expects($this->exactly(3))->method('convert')->willReturnMap($map);
+
+        $this->providerMock->expects($this->once())
+            ->method('getLinkedProducts')
+            ->with($this->productMock)
+            ->willReturn(
+                [
+                    $linkedProductOneMock,
+                    $linkedProductTwoMock,
+                    $linkedProductThreeMock
+                ]
+            );
+
+        $expectedResult = [
+            2 => ['name' => 'Product Two', 'position' => 2],
+            3 => ['name' => 'Product Three', 'position' => 2],
+            10 => ['name' => 'Product One', 'position' => 10],
+        ];
+
+        $actualResult = $this->model->getCollection($this->productMock, 'crosssell');
+
+        $this->assertEquals($expectedResult, $actualResult, 'Sort order of linked products in incorrect');
+    }
+
+    /**
+     * Test exception when collection provider is not configured for product link type.
+     *
+     * @expectedException \Magento\Framework\Exception\NoSuchEntityException
+     * @expectedExceptionMessage Collection provider is not registered
+     */
+    public function testGetCollectionWithMissingProviders()
+    {
+        $this->model->getCollection($this->productMock, 'upsell');
+    }
+}
diff --git a/app/code/Magento/Cms/Block/Adminhtml/Wysiwyg/Images/Tree.php b/app/code/Magento/Cms/Block/Adminhtml/Wysiwyg/Images/Tree.php
index 1b5e4f54f552c..7e52e2bdb4702 100644
--- a/app/code/Magento/Cms/Block/Adminhtml/Wysiwyg/Images/Tree.php
+++ b/app/code/Magento/Cms/Block/Adminhtml/Wysiwyg/Images/Tree.php
@@ -26,20 +26,30 @@ class Tree extends \Magento\Backend\Block\Template
      */
     protected $_cmsWysiwygImages = null;
 
+    /**
+     * @var \Magento\Framework\Serialize\Serializer\Json
+     */
+    private $serializer;
+
     /**
      * @param \Magento\Backend\Block\Template\Context $context
      * @param \Magento\Cms\Helper\Wysiwyg\Images $cmsWysiwygImages
      * @param \Magento\Framework\Registry $registry
      * @param array $data
+     * @param \Magento\Framework\Serialize\Serializer\Json|null $serializer
+     * @throws \RuntimeException
      */
     public function __construct(
         \Magento\Backend\Block\Template\Context $context,
         \Magento\Cms\Helper\Wysiwyg\Images $cmsWysiwygImages,
         \Magento\Framework\Registry $registry,
-        array $data = []
+        array $data = [],
+        \Magento\Framework\Serialize\Serializer\Json $serializer = null
     ) {
         $this->_coreRegistry = $registry;
         $this->_cmsWysiwygImages = $cmsWysiwygImages;
+        $this->serializer = $serializer ?: \Magento\Framework\App\ObjectManager::getInstance()
+            ->get(\Magento\Framework\Serialize\Serializer\Json::class);
         parent::__construct($context, $data);
     }
 
@@ -65,7 +75,7 @@ public function getTreeJson()
                 'cls' => 'folder',
             ];
         }
-        return \Zend_Json::encode($jsonArray);
+        return $this->serializer->serialize($jsonArray);
     }
 
     /**
diff --git a/app/code/Magento/Customer/Block/Account/AuthenticationPopup.php b/app/code/Magento/Customer/Block/Account/AuthenticationPopup.php
index a0f94e1b8f733..eefec4c35679c 100644
--- a/app/code/Magento/Customer/Block/Account/AuthenticationPopup.php
+++ b/app/code/Magento/Customer/Block/Account/AuthenticationPopup.php
@@ -15,16 +15,26 @@ class AuthenticationPopup extends \Magento\Framework\View\Element\Template
      */
     protected $jsLayout;
 
+    /**
+     * @var \Magento\Framework\Serialize\Serializer\Json
+     */
+    private $serializer;
+
     /**
      * @param \Magento\Framework\View\Element\Template\Context $context
      * @param array $data
+     * @param \Magento\Framework\Serialize\Serializer\Json|null $serializer
+     * @throws \RuntimeException
      */
     public function __construct(
         \Magento\Framework\View\Element\Template\Context $context,
-        array $data = []
+        array $data = [],
+        \Magento\Framework\Serialize\Serializer\Json $serializer = null
     ) {
         parent::__construct($context, $data);
         $this->jsLayout = isset($data['jsLayout']) && is_array($data['jsLayout']) ? $data['jsLayout'] : [];
+        $this->serializer = $serializer ?: \Magento\Framework\App\ObjectManager::getInstance()
+            ->get(\Magento\Framework\Serialize\Serializer\Json::class);
     }
 
     /**
@@ -32,7 +42,7 @@ public function __construct(
      */
     public function getJsLayout()
     {
-        return \Zend_Json::encode($this->jsLayout);
+        return $this->serializer->serialize($this->jsLayout);
     }
 
     /**
@@ -50,6 +60,18 @@ public function getConfig()
         ];
     }
 
+    /**
+     * Returns popup config in JSON format.
+     *
+     * Added in scope of https://github.com/magento/magento2/pull/8617
+     *
+     * @return bool|string
+     */
+    public function getSerializedConfig()
+    {
+        return $this->serializer->serialize($this->getConfig());
+    }
+
     /**
      * Is autocomplete enabled for storefront
      *
diff --git a/app/code/Magento/Customer/Test/Unit/Block/Account/AuthenticationPopupTest.php b/app/code/Magento/Customer/Test/Unit/Block/Account/AuthenticationPopupTest.php
index 67a3fb8f3a576..40f770ab9fbd4 100644
--- a/app/code/Magento/Customer/Test/Unit/Block/Account/AuthenticationPopupTest.php
+++ b/app/code/Magento/Customer/Test/Unit/Block/Account/AuthenticationPopupTest.php
@@ -31,6 +31,9 @@ class AuthenticationPopupTest extends \PHPUnit_Framework_TestCase
     /** @var UrlInterface|\PHPUnit_Framework_MockObject_MockObject */
     private $urlBuilderMock;
 
+    /** @var \Magento\Framework\Serialize\Serializer\Json|\PHPUnit_Framework_MockObject_MockObject */
+    private $serializerMock;
+
     protected function setUp()
     {
         $this->contextMock = $this->getMockBuilder(Context::class)
@@ -72,8 +75,13 @@ function ($string) {
             ->method('getEscaper')
             ->willReturn($escaperMock);
 
+        $this->serializerMock = $this->getMockBuilder(\Magento\Framework\Serialize\Serializer\Json::class)
+            ->getMock();
+
         $this->model = new AuthenticationPopup(
-            $this->contextMock
+            $this->contextMock,
+            [],
+            $this->serializerMock
         );
     }
 
@@ -83,6 +91,7 @@ function ($string) {
      * @param string $registerUrl
      * @param string $forgotUrl
      * @param array $result
+     * @throws \PHPUnit_Framework_Exception
      *
      * @dataProvider dataProviderGetConfig
      */
@@ -172,4 +181,51 @@ public function dataProviderGetConfig()
             ],
         ];
     }
+
+    /**
+     * @param mixed $isAutocomplete
+     * @param string $baseUrl
+     * @param string $registerUrl
+     * @param string $forgotUrl
+     * @param array $result
+     * @throws \PHPUnit_Framework_Exception
+     *
+     * @dataProvider dataProviderGetConfig
+     */
+    public function testGetSerializedConfig($isAutocomplete, $baseUrl, $registerUrl, $forgotUrl, array $result)
+    {
+        $this->scopeConfigMock->expects($this->any())
+            ->method('getValue')
+            ->with(Form::XML_PATH_ENABLE_AUTOCOMPLETE, ScopeInterface::SCOPE_STORE, null)
+            ->willReturn($isAutocomplete);
+
+        /** @var StoreInterface||\PHPUnit_Framework_MockObject_MockObject $storeMock */
+        $storeMock = $this->getMockBuilder(StoreInterface::class)
+            ->setMethods(['getBaseUrl'])
+            ->getMockForAbstractClass();
+
+        $this->storeManagerMock->expects($this->any())
+            ->method('getStore')
+            ->with(null)
+            ->willReturn($storeMock);
+
+        $storeMock->expects($this->any())
+            ->method('getBaseUrl')
+            ->willReturn($baseUrl);
+
+        $this->urlBuilderMock->expects($this->any())
+            ->method('getUrl')
+            ->willReturnMap(
+                [
+                    ['customer/account/create', [], $registerUrl],
+                    ['customer/account/forgotpassword', [], $forgotUrl],
+                ]
+            );
+        $this->serializerMock->expects($this->any())->method('serialize')
+            ->willReturn(
+                json_encode($this->model->getConfig())
+            );
+
+        $this->assertEquals(json_encode($result), $this->model->getSerializedConfig());
+    }
 }
diff --git a/app/code/Magento/Customer/view/frontend/templates/account/authentication-popup.phtml b/app/code/Magento/Customer/view/frontend/templates/account/authentication-popup.phtml
index bcf0cc92bc912..20ea488931398 100644
--- a/app/code/Magento/Customer/view/frontend/templates/account/authentication-popup.phtml
+++ b/app/code/Magento/Customer/view/frontend/templates/account/authentication-popup.phtml
@@ -10,7 +10,7 @@
 ?>
 <div id="authenticationPopup" data-bind="scope:'authenticationPopup'" style="display: none;">
     <script>
-        window.authenticationPopup = <?php /* @noEscape */ echo \Zend_Json::encode($block->getConfig()); ?>;
+        window.authenticationPopup = <?php /* @noEscape */ echo $block->getSerializedConfig(); ?>;
     </script>
     <!-- ko template: getTemplate() --><!-- /ko -->
     <script type="text/x-magento-init">
diff --git a/dev/tests/integration/etc/di/preferences/ce.php b/dev/tests/integration/etc/di/preferences/ce.php
index a01ac8caaf977..158d94d503df2 100644
--- a/dev/tests/integration/etc/di/preferences/ce.php
+++ b/dev/tests/integration/etc/di/preferences/ce.php
@@ -22,6 +22,5 @@
     \Magento\Framework\App\ResourceConnection\ConnectionAdapterInterface::class =>
         \Magento\TestFramework\Db\ConnectionAdapter::class,
     \Magento\Framework\Filesystem\DriverInterface::class => \Magento\Framework\Filesystem\Driver\File::class,
-    \Magento\Framework\App\Config\ScopeConfigInterface::class => \Magento\TestFramework\App\Config::class,
-    \Magento\Captcha\Model\DefaultModel::class => \Magento\TestFramework\Captcha\DefaultModel::class,
+    \Magento\Framework\App\Config\ScopeConfigInterface::class => \Magento\TestFramework\App\Config::class
 ];
diff --git a/dev/tests/integration/framework/Magento/TestFramework/Captcha/DefaultModel.php b/dev/tests/integration/framework/Magento/TestFramework/Captcha/DefaultModel.php
deleted file mode 100644
index a3620ee3a968a..0000000000000
--- a/dev/tests/integration/framework/Magento/TestFramework/Captcha/DefaultModel.php
+++ /dev/null
@@ -1,44 +0,0 @@
-<?php
-/**
- * Copyright © 2013-2017 Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
- */
-namespace Magento\TestFramework\Captcha;
-
-/**
- * Implementation of \Zend\Captcha\Image for integration test environment.
- *
- * With introducing "zendframework/zend-captcha": "~2.4.6" (see https://github.com/magento/magento2/pull/8356)
- * validation happens in \Zend\Captcha\Image class constructor that blocks testing on Travis CI, even for cases
- * when this functionality is not needed.
- * For test environment that supports freetype functional behaviour should not be changed.
- */
-class DefaultModel extends \Magento\Captcha\Model\DefaultModel
-{
-    /**
-     * Do not pass onto the parent constructor as imageftbbox is not initialized on travis
-     *
-     * @param \Magento\Framework\Session\SessionManagerInterface $session
-     * @param \Magento\Captcha\Helper\Data $captchaData
-     * @param \Magento\Captcha\Model\ResourceModel\LogFactory $resLogFactory
-     * @param string $formId
-     */
-    public function __construct(
-        \Magento\Framework\Session\SessionManagerInterface $session,
-        \Magento\Captcha\Helper\Data $captchaData,
-        \Magento\Captcha\Model\ResourceModel\LogFactory $resLogFactory,
-        $formId
-    ) {
-        /**
-         * Workaround for test environments that do not support freetype.
-         */
-        if (function_exists("imageftbbox")) {
-            parent::__construct($session, $captchaData, $resLogFactory, $formId);
-        } else {
-            $this->session = $session;
-            $this->captchaData = $captchaData;
-            $this->resLogFactory = $resLogFactory;
-            $this->formId = $formId;
-        }
-    }
-}
diff --git a/dev/tests/integration/testsuite/Magento/Framework/Image/Adapter/InterfaceTest.php b/dev/tests/integration/testsuite/Magento/Framework/Image/Adapter/InterfaceTest.php
index fa0b520aa8eef..e50874ccb8304 100644
--- a/dev/tests/integration/testsuite/Magento/Framework/Image/Adapter/InterfaceTest.php
+++ b/dev/tests/integration/testsuite/Magento/Framework/Image/Adapter/InterfaceTest.php
@@ -547,7 +547,9 @@ public function cropDataProvider()
      */
     public function testCreatePngFromString($pixel1, $expectedColor1, $pixel2, $expectedColor2, $adapterType)
     {
-        if (!function_exists('imagettfbbox')) {
+        if (!function_exists('imagettfbbox')
+            || (getenv('TRAVIS') && getenv('TRAVIS_PHP_VERSION') == '5.6.29')
+        ) {
             $this->markTestSkipped('Workaround for problem with imagettfbbox() function on Travis');
         }
         $adapter = $this->_getAdapter($adapterType);