diff --git a/.travis.yml b/.travis.yml
index 80b64a5..96ba9fc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,7 @@
 language: php
 
 php:
+  - 5.5
   - 5.6
   - 7.0
   - 7.1
diff --git a/tests/CredisClusterTest.php b/tests/CredisClusterTest.php
index 7059928..c72d629 100644
--- a/tests/CredisClusterTest.php
+++ b/tests/CredisClusterTest.php
@@ -92,7 +92,7 @@ public function testMasterSlave()
       $this->waitForSlaveReplication();
       $this->assertEquals('value',$this->cluster->client('slave')->get('key'));
       $this->assertEquals('value',$this->cluster->get('key'));
-      $this->expectException('CredisException','read-only slaves should not be writeable');
+      $this->expectException('CredisException');
       $this->assertFalse($this->cluster->client('slave')->set('key2','value'));
   }
   public function testMasterWithoutSlavesAndWriteOnlyFlag()
diff --git a/tests/CredisTestCommon.php b/tests/CredisTestCommon.php
index 8c64371..b50e11a 100644
--- a/tests/CredisTestCommon.php
+++ b/tests/CredisTestCommon.php
@@ -1,7 +1,7 @@
 <?php
 // backward compatibility (https://stackoverflow.com/a/42828632/187780)
 if (!class_exists('\PHPUnit\Framework\TestCase') && class_exists('\PHPUnit_Framework_TestCase')) {
-    //class_alias('\PHPUnit_Framework_TestCase', '\PHPUnit\Framework\TestCase');
+    class_alias('\PHPUnit_Framework_TestCase', '\PHPUnit\Framework\TestCase');
 }
 
 class CredisTestCommon extends \PHPUnit\Framework\TestCase
@@ -150,4 +150,34 @@ public static function tearDownAfterClass()
             @copy('redis-sentinel.conf.bak','redis-sentinel.conf');
         }
     }
+    
+    /**
+     * Polyfill for older PHPUnit
+     */
+    public function createMock($class)
+    {
+        if (method_exists($this, 'getMock')) {
+            return $this->getMock($class);
+        } else {
+            return parent::createMock($class);
+        }
+    }
+    
+    /**
+     * Polyfill for older PHPUnit
+     */
+    public function expectException($class, $message = NULL, $code = NULL)
+    {
+        if (method_exists($this, 'setExpectedException')) {
+            $this->setExpectedException($class, $message, $code);
+        } else {
+            parent::expectException($class);
+            if ($message !== null) {
+                $this->expectExceptionMessage($message);
+            }
+            if ($code !== null) {
+                $this->expectExceptionCode($code);
+            }
+        }
+    }
 }