diff --git a/lib/Config/AccessControl.php b/lib/Config/AccessControl.php
index 9eecc661e5..2ce6039fc8 100644
--- a/lib/Config/AccessControl.php
+++ b/lib/Config/AccessControl.php
@@ -14,48 +14,41 @@ class AccessControl {
   const PERMISSION_MANAGE_SEGMENTS = 'mailpoet_manage_segments';
   const NO_ACCESS_RESTRICTION = 'mailpoet_no_access_restriction';
 
-  /** @var WPFunctions */
-  private $wp;
-
-  function __construct(WPFunctions $wp) {
-    $this->wp = $wp;
-  }
-
   function getDefaultPermissions() {
     return array(
-      self::PERMISSION_ACCESS_PLUGIN_ADMIN => $this->wp->applyFilters(
+      self::PERMISSION_ACCESS_PLUGIN_ADMIN => WPFunctions::get()->applyFilters(
         'mailpoet_permission_access_plugin_admin',
         array(
           'administrator',
           'editor'
         )
       ),
-      self::PERMISSION_MANAGE_SETTINGS => $this->wp->applyFilters(
+      self::PERMISSION_MANAGE_SETTINGS => WPFunctions::get()->applyFilters(
         'mailpoet_permission_manage_settings',
         array(
           'administrator'
         )
       ),
-      self::PERMISSION_MANAGE_EMAILS => $this->wp->applyFilters(
+      self::PERMISSION_MANAGE_EMAILS => WPFunctions::get()->applyFilters(
         'mailpoet_permission_manage_emails',
         array(
           'administrator',
           'editor'
         )
       ),
-      self::PERMISSION_MANAGE_SUBSCRIBERS => $this->wp->applyFilters(
+      self::PERMISSION_MANAGE_SUBSCRIBERS => WPFunctions::get()->applyFilters(
         'mailpoet_permission_manage_subscribers',
         array(
           'administrator'
         )
       ),
-      self::PERMISSION_MANAGE_FORMS => $this->wp->applyFilters(
+      self::PERMISSION_MANAGE_FORMS => WPFunctions::get()->applyFilters(
         'mailpoet_permission_manage_forms',
         array(
           'administrator'
         )
       ),
-      self::PERMISSION_MANAGE_SEGMENTS => $this->wp->applyFilters(
+      self::PERMISSION_MANAGE_SEGMENTS => WPFunctions::get()->applyFilters(
         'mailpoet_permission_manage_segments',
         array(
           'administrator'
diff --git a/lib/Form/Block/Base.php b/lib/Form/Block/Base.php
index af27b47b05..32fb7ce202 100644
--- a/lib/Form/Block/Base.php
+++ b/lib/Form/Block/Base.php
@@ -4,6 +4,7 @@ namespace MailPoet\Form\Block;
 
 use MailPoet\Form\Util\FieldNameObfuscator;
 use MailPoet\Models\ModelValidator;
+use MailPoet\WP\Functions as WPFunctions;
 
 abstract class Base {
   protected static function getInputValidation($block, $extra_rules = array()) {
diff --git a/lib/WP/Functions.php b/lib/WP/Functions.php
index 58a4b7a01a..3e99808886 100644
--- a/lib/WP/Functions.php
+++ b/lib/WP/Functions.php
@@ -482,4 +482,16 @@ class Functions {
   function hasFilter() {
     return call_user_func_array('has_filter', func_get_args());
   }
+
+  function wcPrice() {
+    return call_user_func_array('wc_price', func_get_args());
+  }
+
+  function wcGetOrder() {
+    return call_user_func_array('wc_get_order', func_get_args());
+  }
+  function wcGetCustomerOrderCount() {
+    return call_user_func_array('wc_get_customer_order_count', func_get_args());
+  }
+
 }
diff --git a/lib/WP/Posts.php b/lib/WP/Posts.php
index 6ec3c2a6a5..98d26ead67 100644
--- a/lib/WP/Posts.php
+++ b/lib/WP/Posts.php
@@ -8,7 +8,7 @@ class Posts {
   static function getTerms($args) {
     // Since WordPress 4.5.0 signature of get_terms changed to require
     // one argument array, where taxonomy is key of that array
-    if (version_compare(get_bloginfo('version'), '4.5.0', '>=')) {
+    if (version_compare(WPFunctions::get()->getBloginfo('version'), '4.5.0', '>=')) {
       return WPFunctions::get()->getTerms($args);
     } else {
       $taxonomy = $args['taxonomy'];
diff --git a/tests/integration/Config/AccessControlTest.php b/tests/integration/Config/AccessControlTest.php
index ae82c4f963..8c129e48dd 100644
--- a/tests/integration/Config/AccessControlTest.php
+++ b/tests/integration/Config/AccessControlTest.php
@@ -2,9 +2,8 @@
 
 namespace MailPoet\Test\Config;
 
-use Codeception\Util\Stub;
+use Codeception\Stub;
 use Codeception\Stub\Expected;
-use Helper\WordPress as WPHelper;
 use MailPoet\Config\AccessControl;
 use MailPoet\WP\Functions as WPFunctions;
 
@@ -15,7 +14,7 @@ class AccessControlTest extends \MailPoetTest {
 
   function _before() {
     parent::_before();
-    $this->access_control = new AccessControl(new WPFunctions());
+    $this->access_control = new AccessControl;
   }
 
   function testItAllowsSettingCustomPermissions() {
@@ -88,17 +87,16 @@ class AccessControlTest extends \MailPoetTest {
   }
 
   function testItValidatesIfUserHasCapability() {
-    $wp_mock = Stub::makeEmpty(
-      new WPFunctions(),
-      ['currentUserCan' => Expected::once(true)]
-    );
-    $access_control = new AccessControl($wp_mock);
     $capability = 'some_capability';
+    $access_control = new AccessControl();
+    WPFunctions::set(Stub::make(new WPFunctions, [
+      'currentUserCan' => true
+    ]));
 
     expect($access_control->validatePermission($capability))->true();
   }
 
   function _after() {
-    WPHelper::releaseAllFunctions();
+    WPFunctions::set(new WPFunctions);
   }
 }
diff --git a/tests/integration/Twig/FunctionsTest.php b/tests/integration/Twig/FunctionsTest.php
index 7c39b37164..30913afa29 100644
--- a/tests/integration/Twig/FunctionsTest.php
+++ b/tests/integration/Twig/FunctionsTest.php
@@ -2,8 +2,9 @@
 
 namespace MailPoet\Test\Twig;
 
-use AspectMock\Test as Mock;
+use Codeception\Util\Stub;
 use MailPoet\Twig\Functions;
+use MailPoet\WP\Functions as WPFunctions;
 
 class FunctionsTest extends \MailPoetTest {
   function testItExecutesIsRtlFunction() {
@@ -11,12 +12,20 @@ class FunctionsTest extends \MailPoetTest {
     $twig = new \Twig_Environment(new \Twig_Loader_Array($template));
     $twig->addExtension(new Functions());
 
-    Mock::func('MailPoet\Twig', 'is_rtl', true);
+    WPFunctions::set(Stub::make(new WPFunctions, [
+      'isRtl' => true
+    ]));
     $result = $twig->render('template');
     expect($result)->equals('rtl');
 
-    Mock::func('MailPoet\Twig', 'is_rtl', false);
+    WPFunctions::set(Stub::make(new WPFunctions, [
+      'isRtl' => false
+    ]));
     $result = $twig->render('template');
     expect($result)->isEmpty();
   }
+
+  function _after() {
+    WPFunctions::set(new WPFunctions);
+  }
 }
diff --git a/tests/integration/WP/FunctionsTest.php b/tests/integration/WP/FunctionsTest.php
index 09f6fa5eb5..57c1f2d05c 100644
--- a/tests/integration/WP/FunctionsTest.php
+++ b/tests/integration/WP/FunctionsTest.php
@@ -42,25 +42,6 @@ class FunctionsTest extends \MailPoetTest {
     return $this->ids[] = $id;
   }
 
-  function testItCanGetImageInfo() {
-    expect(
-      function_exists('wp_generate_attachment_metadata')
-    )->true();
-
-    $filename = 'tests/_data/test-image.jpg';
-    $contents = file_get_contents($filename);
-
-    $upload = wp_upload_bits(basename($filename), null, $contents);
-    $id = $this->makeAttachment($upload);
-    expect($id)->notEmpty();
-
-    $image = $this->wp->getImageInfo($id);
-    expect($image[1])->equals(Env::NEWSLETTER_CONTENT_WIDTH);
-
-    wp_delete_attachment($id, $force_delete = true);
-  }
-
-
   function testItCanProcessActions() {
     $test_value = array('abc', 'def');
     $test_value2 = new \stdClass;
diff --git a/tests/unit/WP/PostsTest.php b/tests/unit/WP/PostsTest.php
index 6171a0f3b4..37dadd515b 100644
--- a/tests/unit/WP/PostsTest.php
+++ b/tests/unit/WP/PostsTest.php
@@ -1,8 +1,9 @@
 <?php
 namespace MailPoet\Test\WP;
 
-use Helper\WordPress as WordPressHelper;
 use MailPoet\WP\Posts;
+use Codeception\Util\Stub;
+use MailPoet\WP\Functions as WPFunctions;
 
 class PostsTest extends \MailPoetUnitTest {
 
@@ -12,16 +13,17 @@ class PostsTest extends \MailPoetUnitTest {
       'hide_empty' => true
     );
 
-    WordPressHelper::interceptFunction('get_bloginfo', function($key) {
-      return '4.6.0';
-    });
-
-    WordPressHelper::interceptFunction('get_terms', function($key) {
-      return array(
-        'call check' => 'get_terms called',
-        'arguments' => func_get_args()
-      );
-    });
+    WPFunctions::set(Stub::make(new WPFunctions, [
+      'getBloginfo' => function($key) {
+        return '4.6.0';
+      },
+      'getTerms' => function($key) {
+        return array(
+          'call check' => 'get_terms called',
+          'arguments' => func_get_args()
+        );
+      }
+    ]));
 
     $result = Posts::getTerms($args);
     expect($result['call check'])->equals('get_terms called');
@@ -34,16 +36,17 @@ class PostsTest extends \MailPoetUnitTest {
       'hide_empty' => true
     );
 
-    WordPressHelper::interceptFunction('get_bloginfo', function($key) {
-      return '4.4.0';
-    });
-
-    WordPressHelper::interceptFunction('get_terms', function($key) {
-      return array(
-        'call check' => 'get_terms called',
-        'arguments' => func_get_args()
-      );
-    });
+    WPFunctions::set(Stub::make(new WPFunctions, [
+      'getBloginfo' => function($key) {
+        return '4.4.0';
+      },
+      'getTerms' => function($key) {
+        return array(
+          'call check' => 'get_terms called',
+          'arguments' => func_get_args()
+        );
+      }
+    ]));
 
     $result = Posts::getTerms($args);
     expect($result['call check'])->equals('get_terms called');
@@ -51,7 +54,4 @@ class PostsTest extends \MailPoetUnitTest {
     expect($result['arguments'][1])->equals(array_diff_key($args, array('taxonomy' => '')));
   }
 
-  function _afterStep() {
-    WordPressHelper::releaseAllFunctions();
-  }
 }