diff --git a/includes/lib/transifex-live-integration-rewrite.php b/includes/lib/transifex-live-integration-rewrite.php
index 4086e4a2..e6cdede7 100644
--- a/includes/lib/transifex-live-integration-rewrite.php
+++ b/includes/lib/transifex-live-integration-rewrite.php
@@ -40,6 +40,7 @@ public function __construct( $settings, $rewrite_options ) {
 		Plugin_Debug::logTrace();
 		include_once TRANSIFEX_LIVE_INTEGRATION_DIRECTORY_BASE . '/includes/common/transifex-live-integration-validators.php';
 		include_once TRANSIFEX_LIVE_INTEGRATION_DIRECTORY_BASE . '/includes/override/transifex-live-integration-generate-rewrite-rules.php';
+		include_once TRANSIFEX_LIVE_INTEGRATION_DIRECTORY_BASE . '/includes/lib/transifex-live-integration-wp-services.php';
 		$this->rewrite_options = [ ];
 		$this->languages_regex = $settings['languages_regex'];
 		$this->source_language = $settings['source_language'];
@@ -97,6 +98,7 @@ public function __construct( $settings, $rewrite_options ) {
 				$this->rewrite_pattern = $pattern;
 			}
 		}
+		$this->wp_services = new Transifex_Live_Integration_WP_Services();
 	}
 
 	public function get_language_url( $atts ) {
@@ -146,7 +148,7 @@ function wp_hook() {
 	 * @return string Returns modified link
 	 */
 
-	static function reverse_hard_link( $lang, $link, $languages_map, $source_lang,
+	function reverse_hard_link( $lang, $link, $languages_map, $source_lang,
 			$pattern ) {
 		Plugin_Debug::logTrace();
 		if ( !(isset( $pattern )) ) {
@@ -170,7 +172,7 @@ static function reverse_hard_link( $lang, $link, $languages_map, $source_lang,
 		if ( count( $m ) > 1 ) {
 			$link = str_replace( $m[1], $lang, $m[0] );
 		} else {
-			$site_host = parse_url(site_url())['host'];
+			$site_host = parse_url($this->wp_services->get_site_url())['host'];
 			$parsed_url = parse_url($link);
 			$link_host = isset($parsed_url['host']) ? $parsed_url['host'] : '';
 			// change only wordpress links - not links reffering to other domains
diff --git a/includes/lib/transifex-live-integration-wp-services.php b/includes/lib/transifex-live-integration-wp-services.php
new file mode 100644
index 00000000..c81523b6
--- /dev/null
+++ b/includes/lib/transifex-live-integration-wp-services.php
@@ -0,0 +1,18 @@
+<?php
+
+/*
+ * @package TransifexLiveIntegration
+ */
+
+/**
+ * Provides WP services to other classes.
+ */
+class Transifex_Live_Integration_WP_Services {
+
+    /*
+	 * Wraps WP site_url().
+	 */
+	function get_site_url() {
+		return site_url();
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/BaseTestCase.php b/tests/unit/BaseTestCase.php
new file mode 100644
index 00000000..27c761c4
--- /dev/null
+++ b/tests/unit/BaseTestCase.php
@@ -0,0 +1,15 @@
+<?php
+/*
+ * This class caters for the different PHPUnit versions between production (CI)
+ * and development.
+ * To execute unit tests use :
+ * 
+ *   php codecept.phar run unit --debug
+ */
+if (class_exists('\PHPUnit_Framework_TestCase')) {
+	// php 5.6, production - CI environment
+	class BaseTestCase extends \PHPUnit_Framework_TestCase {}
+} else {
+	// php 7+, dev environment
+	class BaseTestCase extends PHPunit\Framework\TestCase {}
+}
\ No newline at end of file
diff --git a/tests/unit/CalculateDefaultsTest.php b/tests/unit/CalculateDefaultsTest.php
index c85c3946..9f29c913 100644
--- a/tests/unit/CalculateDefaultsTest.php
+++ b/tests/unit/CalculateDefaultsTest.php
@@ -1,6 +1,7 @@
 <?php
+include_once __DIR__ .'/BaseTestCase.php';
 
-class CalculateDefaultsTest extends \PHPUnit_Framework_TestCase
+class CalculateDefaultsTest extends BaseTestCase
 {
     private $data_subdomain;
 	private $data_subdirectory;
diff --git a/tests/unit/GenerateLanguageUrlMapTest.php b/tests/unit/GenerateLanguageUrlMapTest.php
index 73c92a57..59766e1e 100644
--- a/tests/unit/GenerateLanguageUrlMapTest.php
+++ b/tests/unit/GenerateLanguageUrlMapTest.php
@@ -1,6 +1,7 @@
 <?php
+include_once __DIR__ .'/BaseTestCase.php';
 
-class GenerateLanguageUrlMapTest extends \PHPUnit_Framework_TestCase
+class GenerateLanguageUrlMapTest extends BaseTestCase
 {
 
     private $data;
diff --git a/tests/unit/GenerateTokenizedUrlTest.php b/tests/unit/GenerateTokenizedUrlTest.php
index ff6323c0..5c27c105 100644
--- a/tests/unit/GenerateTokenizedUrlTest.php
+++ b/tests/unit/GenerateTokenizedUrlTest.php
@@ -1,6 +1,7 @@
 <?php
+include_once __DIR__ .'/BaseTestCase.php';
 
-class GenerateTokenizedUrlTest extends \PHPUnit_Framework_TestCase
+class GenerateTokenizedUrlTest extends BaseTestCase
 {
 
     private $data;
diff --git a/tests/unit/PrerenderCheckTest.php b/tests/unit/PrerenderCheckTest.php
index 76958658..6d408485 100644
--- a/tests/unit/PrerenderCheckTest.php
+++ b/tests/unit/PrerenderCheckTest.php
@@ -1,6 +1,7 @@
 <?php
+include_once __DIR__ .'/BaseTestCase.php';
 
-class PrerenderCheckTest extends \PHPUnit_Framework_TestCase
+class PrerenderCheckTest extends BaseTestCase
 {
 
     private $data;
diff --git a/tests/unit/ReplaceSubdomainTest.php b/tests/unit/ReplaceSubdomainTest.php
index 7a806da4..a80198ed 100644
--- a/tests/unit/ReplaceSubdomainTest.php
+++ b/tests/unit/ReplaceSubdomainTest.php
@@ -1,6 +1,7 @@
 <?php
+include_once __DIR__ .'/BaseTestCase.php';
 
-class ReplaceSubdomainTest extends \PHPUnit_Framework_TestCase
+class ReplaceSubdomainTest extends BaseTestCase
 {
 
     private $data;
@@ -9,6 +10,7 @@ protected function setUp()
     {
         include_once './includes/common/plugin-debug.php';
         include_once './includes/common/transifex-live-integration-common.php';
+        include_once './includes/transifex-live-integration-util.php';
         $this->data = [
         [
         'page_url' => 'https://www.foo.bar/about/',
diff --git a/tests/unit/ReverseHardLinkTest.php b/tests/unit/ReverseHardLinkTest.php
index 9e8d0bdb..16b21b55 100644
--- a/tests/unit/ReverseHardLinkTest.php
+++ b/tests/unit/ReverseHardLinkTest.php
@@ -1,21 +1,32 @@
 <?php
+/**
+ * Execute this test setting <environment> either as 'dev' or 'prod' :
+ * 
+ *   export TEST_ENV=<environment>
+ *   php codecept.phar run unit --debug ReverseHardLinkTest
+ */
+include_once __DIR__ .'/BaseTestCase.php';
 
-class ReverseHardLinkTest extends \PHPUnit_Framework_TestCase {
+class ReverseHardLinkTest extends BaseTestCase {
 
 	private $data;
 
 	protected function setUp() {
 		include_once './includes/common/plugin-debug.php';
 		include_once './includes/lib/transifex-live-integration-rewrite.php';
+		include_once './includes/lib/transifex-live-integration-wp-services.php';
+		include_once '../../../wp-load.php';
 		$this->data = [[ //1
-		'lang' => 'zh_CN',
-		'link' => 'http://www.mydomain.com/page-markup-and-formatting',
-		'languages_map' => ["zh_CN" => "zh_CN", "de_DE" => "de_DE" ],
-		'souce_lang' => 'en',
-		'pattern' => '/http:\/\/www.mydomain.com\/(zh_CN|de_DE)\//',
-		'result' => 'http://www.mydomain.com/zh_CN/page-markup-and-formatting'
+				'host' => 'http://www.mydomain.com',
+				'lang' => 'zh_CN',
+				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
+				'languages_map' => ["zh_CN" => "zh_CN", "de_DE" => "de_DE" ],
+				'souce_lang' => 'en',
+				'pattern' => '/http:\/\/www.mydomain.com\/(zh_CN|de_DE)\//',
+				'result' => 'http://www.mydomain.com/zh_CN/page-markup-and-formatting'
 			],
 			[ //2
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'zh_CN',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
 				'languages_map' => ["zh_CN" => "zh_CN", "de_DE" => "de_DE" ],
@@ -24,6 +35,7 @@ protected function setUp() {
 				'result' => 'http://www.mydomain.com/page-markup-and-formatting'
 			],
 			[ //3
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'zh_HK',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
 				'languages_map' => ["zh_CN" => "zh_CN", "de_DE" => "de_DE" ],
@@ -32,6 +44,7 @@ protected function setUp() {
 				'result' => 'http://www.mydomain.com/page-markup-and-formatting'
 			],
 			[ //4
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'cn',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
 				'languages_map' => ["zh_CN" => "cn", "de_DE" => "de_DE" ],
@@ -40,6 +53,7 @@ protected function setUp() {
 				'result' => 'http://www.mydomain.com/cn/page-markup-and-formatting'
 			],
 			[ //5
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'zh_CN',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
 				'languages_map' => [ ],
@@ -48,6 +62,7 @@ protected function setUp() {
 				'result' => 'http://www.mydomain.com/page-markup-and-formatting'
 			],
 			[ //6
+				'host' => 'http://www.mydomain.com',
 				'lang' => null,
 				'link' => 'http://www.mydomain.com/',
 				'languages_map' => null,
@@ -56,6 +71,7 @@ protected function setUp() {
 				'result' => 'http://www.mydomain.com/'
 			],
 			[ //7
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'zh_CN',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
 				'languages_map' => ["zh_CN" => "cn", "de_DE" => "de_DE" ],
@@ -64,6 +80,7 @@ protected function setUp() {
 				'result' => 'http://www.mydomain.com/page-markup-and-formatting'
 			],
 			[ //8
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'zh_CN',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
 				'languages_map' => ["zh_CN" => "zh_CN", "de_DE" => "de_DE" ],
@@ -72,6 +89,7 @@ protected function setUp() {
 				'result' => 'http://zh_CN.mydomain.com/page-markup-and-formatting'
 			],
 			[ //9
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'cn',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting',
 				'languages_map' => ["zh_CN" => "cn", "de_DE" => "de_DE" ],
@@ -80,6 +98,7 @@ protected function setUp() {
 				'result' => 'http://cn.mydomain.com/page-markup-and-formatting'
 			],
 			[ //10 plex case
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'de',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting-de',
 				'languages_map' => ["zh_CN" => "cn", "de_DE" => "de" ],
@@ -88,25 +107,37 @@ protected function setUp() {
 				'result' => 'http://www.mydomain.com/de/page-markup-and-formatting-de'
 			],
 			[ //11
+				'host' => 'http://www.mydomain.com',
 				'lang' => 'de',
 				'link' => 'http://www.mydomain.com/page-markup-and-formatting-de',
 				'languages_map' => ["zh_CN" => "cn", "de_DE" => "de" ],
 				'souce_lang' => 'en',
 				'pattern' => '/http:\/\/(cn|de|www).mydomain.com\/.*/',
 				'result' => 'http://de.mydomain.com/page-markup-and-formatting-de'
+			],
+			[ //12 external link, leave intact
+				'host' => 'http://www.mydomain.com',
+				'lang' => 'de',
+				'link' => 'http://www.another.com/page-markup-and-formatting-de',
+				'languages_map' => ["zh_CN" => "cn", "de_DE" => "de" ],
+				'souce_lang' => 'en',
+				'pattern' => '/http:\/\/www.mydomain.com\/(cn|de)\//',
+				'result' => 'http://www.another.com/page-markup-and-formatting-de'
 			]
 		];
 	}
 
 	public function testMe() {
 		$counter = 0;
+		$rewrite = new Transifex_Live_Integration_Rewrite( [], [] );
 		foreach ($this->data as $i) {
 			$counter = $counter + 1;
-			$result = Transifex_Live_Integration_Rewrite::reverse_hard_link(
+			$rewrite->wp_services = \Codeception\Stub::make(Transifex_Live_Integration_WP_Services::class, ['get_site_url' => $i['host']]);
+			$result = $rewrite->reverse_hard_link(
 							$i['lang'], $i['link'], $i['languages_map'], $i['souce_lang'], $i['pattern']
 			);
 
-//            eval(\Psy\sh());
+			// codecept_debug('result:' . $i['result']);
 			$this->assertEquals( $i['result'], $result, 'Test Number:' . $counter );
 		}
 	}