diff --git a/composer.json b/composer.json
index ee5ce7f..1eb79c5 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     }
   ],
   "require": {
-    "php": ">=5.2",
+    "php": ">=5.6",
     "ext-curl": "*",
     "ext-json": "*",
     "ext-mbstring": "*"
@@ -30,6 +30,8 @@
     "phpunit/phpunit": "5.5.*"
   },
   "autoload": {
-    "classmap": ["lib/Shippo/"]
+    "psr-4": {
+      "Shippo\\": "lib/"
+    }
   }
 }
diff --git a/lib/Shippo/Address.php b/lib/Shippo/Address.php
index f2e58e1..f3eec22 100644
--- a/lib/Shippo/Address.php
+++ b/lib/Shippo/Address.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Address extends Shippo_ApiResource
 {
     /**
@@ -13,45 +15,44 @@ public static function classUrl($class)
     {
         return "/v1/addresses";
     }
-    
+
     /**
      * @param array|null $params
      * @param string|null $apiKey
-     *
-     * @return Shippo_Adress Create an Address.
+     * @return static
      */
     public static function create($params = null, $apiKey = null)
     {
         $class = get_class();
         return self::_scopedCreate($class, $params, $apiKey);
     }
-    
+
     /**
-     * @param array|null $params
-     *
-     * @return Shippo_Retrieve Get an address.
+     * @param $id
+     * @param null $apiKey
+     * @return static
      */
     public static function retrieve($id, $apiKey = null)
     {
         $class = get_class();
+
         return self::_scopedRetrieve($class, $id, $apiKey);
     }
-    
+
     /**
-     * @param array|null $params
-     *
-     * @return Shippo_All Get all the addresses.
+     * @param null $params
+     * @param null $apiKey
+     * @return static
      */
     public static function all($params = null, $apiKey = null)
     {
         $class = get_class();
         return self::_scopedAll($class, $params, $apiKey);
     }
-    
+
     /**
-     * @param array|null $params
-     *
-     * @return Shippo_Validate Validate an address.
+     * @param $id
+     * @return mixed
      */
     public static function validate($id)
     {
diff --git a/lib/Shippo/ApiConnectionError.php b/lib/Shippo/ApiConnectionError.php
index 9e8d4c9..96ed0ad 100644
--- a/lib/Shippo/ApiConnectionError.php
+++ b/lib/Shippo/ApiConnectionError.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_ApiConnectionError extends Shippo_Error
 {
 }
diff --git a/lib/Shippo/ApiError.php b/lib/Shippo/ApiError.php
index c2a6ffe..a2bbcc6 100644
--- a/lib/Shippo/ApiError.php
+++ b/lib/Shippo/ApiError.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_ApiError extends Shippo_Error
 {
 }
diff --git a/lib/Shippo/ApiRequestor.php b/lib/Shippo/ApiRequestor.php
index 9943f30..18a08a1 100644
--- a/lib/Shippo/ApiRequestor.php
+++ b/lib/Shippo/ApiRequestor.php
@@ -1,4 +1,7 @@
 <?php
+
+namespace Shippo;
+
 class Shippo_ApiRequestor
 {
     /**
diff --git a/lib/Shippo/ApiResource.php b/lib/Shippo/ApiResource.php
index 9678355..fcf6a90 100644
--- a/lib/Shippo/ApiResource.php
+++ b/lib/Shippo/ApiResource.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 abstract class Shippo_ApiResource extends Shippo_Object
 {
     protected static function _scopedRetrieve($class, $id, $apiKey = null)
@@ -8,7 +10,7 @@ protected static function _scopedRetrieve($class, $id, $apiKey = null)
         $instance->refresh();
         return $instance;
     }
-    
+
     /**
      * @returns Shippo_ApiResource The refreshed resource.
      */
diff --git a/lib/Shippo/AttachedObject.php b/lib/Shippo/AttachedObject.php
index 2c4e083..04c21cc 100644
--- a/lib/Shippo/AttachedObject.php
+++ b/lib/Shippo/AttachedObject.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 // e.g. metadata on Shippo objects.
 class Shippo_AttachedObject extends Shippo_Object
 {
diff --git a/lib/Shippo/AuthenticationError.php b/lib/Shippo/AuthenticationError.php
index 3ab893c..9e05340 100644
--- a/lib/Shippo/AuthenticationError.php
+++ b/lib/Shippo/AuthenticationError.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_AuthenticationError extends Shippo_Error
 {
 }
diff --git a/lib/Shippo/Batch.php b/lib/Shippo/Batch.php
index 46de658..8a6a00c 100644
--- a/lib/Shippo/Batch.php
+++ b/lib/Shippo/Batch.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Batch extends Shippo_ApiResource
 {
     /**
@@ -17,27 +19,24 @@ public static function classUrl($class)
     /**
      * @param array|null $params
      * @param string|null $apiKey
-     *
-     * @return Shippo_Batch Create a batch shipment object 
+     * @return static
      */
     public static function create($params = null, $apiKey = null)
     {
         $class = get_class();
         return self::_scopedCreate($class, $params, $apiKey);
     }
-    
+
     /**
-     * @param string $id
-     * @param string|null $apiKey
-     *
-     * @return Shippo_Retrieve Retrieves a batch shipment 
+     * @param $id
+     * @param null $apiKey
+     * @return static
      */
     public static function retrieve($id, $apiKey = null)
     {
         $class = get_class();
         return self::_scopedRetrieve($class, $id, $apiKey);
     }
-
      /**
      * @param string $id
      * @param array|null $params
diff --git a/lib/Shippo/CarrierAccount.php b/lib/Shippo/CarrierAccount.php
index cb8b03a..b332a0d 100644
--- a/lib/Shippo/CarrierAccount.php
+++ b/lib/Shippo/CarrierAccount.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_CarrierAccount extends Shippo_ApiResource
 {
     /**
@@ -59,4 +61,4 @@ public static function update($id, $params, $apiKey = null)
         return self::_scopedUpdate($class, $id, $params, $apiKey);
     }
 
-}
\ No newline at end of file
+}
diff --git a/lib/Shippo/CurlClient.php b/lib/Shippo/CurlClient.php
index 506f75a..b5f1cc8 100644
--- a/lib/Shippo/CurlClient.php
+++ b/lib/Shippo/CurlClient.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class CurlClient
 {
     private static $instance;
diff --git a/lib/Shippo/CustomsDeclaration.php b/lib/Shippo/CustomsDeclaration.php
index 6476ac9..2bd3484 100644
--- a/lib/Shippo/CustomsDeclaration.php
+++ b/lib/Shippo/CustomsDeclaration.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_CustomsDeclaration extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/CustomsItem.php b/lib/Shippo/CustomsItem.php
index 7b8c3bb..09ba8f5 100644
--- a/lib/Shippo/CustomsItem.php
+++ b/lib/Shippo/CustomsItem.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_CustomsItem extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/Error.php b/lib/Shippo/Error.php
index c70deca..065fa01 100644
--- a/lib/Shippo/Error.php
+++ b/lib/Shippo/Error.php
@@ -1,7 +1,18 @@
 <?php
 
+namespace Shippo;
+
+use Exception;
+
+
 class Shippo_Error extends Exception
 {
+    protected $httpStatus;
+
+    protected $httpBody;
+
+    protected $jsonBody;
+
     public function __construct($message, $httpStatus = null, $httpBody = null, $jsonBody = null)
     {
         parent::__construct($message);
diff --git a/lib/Shippo/InvalidRequestError.php b/lib/Shippo/InvalidRequestError.php
index 9f1e3f4..0170641 100644
--- a/lib/Shippo/InvalidRequestError.php
+++ b/lib/Shippo/InvalidRequestError.php
@@ -1,7 +1,11 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_InvalidRequestError extends Shippo_Error
 {
+    public $param;
+
     public function __construct($message, $param, $httpStatus = null, $httpBody = null, $jsonBody = null)
     {
         parent::__construct($message, $httpStatus, $httpBody, $jsonBody);
diff --git a/lib/Shippo/List.php b/lib/Shippo/List.php
index f8494a5..d1ff017 100644
--- a/lib/Shippo/List.php
+++ b/lib/Shippo/List.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_List extends Shippo_Object
 {
     public function all($params = null)
diff --git a/lib/Shippo/Manifest.php b/lib/Shippo/Manifest.php
index 8855e72..cab1c83 100644
--- a/lib/Shippo/Manifest.php
+++ b/lib/Shippo/Manifest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Manifest extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/Object.php b/lib/Shippo/Object.php
index b1ef537..eb99bd5 100644
--- a/lib/Shippo/Object.php
+++ b/lib/Shippo/Object.php
@@ -1,5 +1,10 @@
 <?php
 
+namespace Shippo;
+
+use ArrayAccess;
+use Shippo\Util\Shippo_Util_Set;
+
 class Shippo_Object implements ArrayAccess
 {
     /**
@@ -56,7 +61,7 @@ public function __construct($id = null, $apiKey = null)
     public function __set($k, $v)
     {
         if ($v === "") {
-            throw new InvalidArgumentException('You cannot set \'' . $k . '\'to an empty string. ' . 'We interpret empty strings as NULL in requests. ' . 'You may set obj->' . $k . ' = NULL to delete the property');
+            throw new \InvalidArgumentException('You cannot set \'' . $k . '\'to an empty string. ' . 'We interpret empty strings as NULL in requests. ' . 'You may set obj->' . $k . ' = NULL to delete the property');
         }
         
         if (self::$nestedUpdatableAttributes->includes($k) && isset($this->$k) && is_array($v)) {
@@ -179,7 +184,7 @@ public function refreshFrom($values, $apiKey, $partial = false)
                 continue;
             
             if (self::$nestedUpdatableAttributes->includes($k) && is_array($v)) {
-                $this->_values[$k] = Shippo_Object::scopedConstructFrom('Shippo_AttachedObject', $v, $apiKey);
+                $this->_values[$k] = Shippo_Object::scopedConstructFrom(Shippo_AttachedObject::class, $v, $apiKey);
             } else {
                 $this->_values[$k] = Shippo_Util::convertToShippoObject($v, $apiKey);
             }
diff --git a/lib/Shippo/Parcel.php b/lib/Shippo/Parcel.php
index c5005b6..53015de 100644
--- a/lib/Shippo/Parcel.php
+++ b/lib/Shippo/Parcel.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Parcel extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/Rate.php b/lib/Shippo/Rate.php
index f3cbb00..6dbb8ea 100644
--- a/lib/Shippo/Rate.php
+++ b/lib/Shippo/Rate.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Rate extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/RateLimitError.php b/lib/Shippo/RateLimitError.php
index 8a01ba0..017fbf0 100644
--- a/lib/Shippo/RateLimitError.php
+++ b/lib/Shippo/RateLimitError.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_RateLimitError extends Shippo_InvalidRequestError
 {
     public function __construct($message, $param, $httpStatus = null, $httpBody = null, $jsonBody = null)
diff --git a/lib/Shippo/Refund.php b/lib/Shippo/Refund.php
index 44c6fa1..33c785d 100644
--- a/lib/Shippo/Refund.php
+++ b/lib/Shippo/Refund.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Refund extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/Shipment.php b/lib/Shippo/Shipment.php
index 05287c9..7092d1a 100644
--- a/lib/Shippo/Shipment.php
+++ b/lib/Shippo/Shipment.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Shipment extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/Shippo.php b/lib/Shippo/Shippo.php
index 7957f9b..d282ea7 100644
--- a/lib/Shippo/Shippo.php
+++ b/lib/Shippo/Shippo.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 abstract class Shippo
 {
     /**
diff --git a/lib/Shippo/SingletonApiResource.php b/lib/Shippo/SingletonApiResource.php
index 732df8a..1c42745 100644
--- a/lib/Shippo/SingletonApiResource.php
+++ b/lib/Shippo/SingletonApiResource.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 abstract class Shippo_SingletonApiResource extends Shippo_ApiResource
 {
     protected static function _scopedSingletonRetrieve($class, $apiKey = null)
diff --git a/lib/Shippo/Track.php b/lib/Shippo/Track.php
index c530a69..d768c99 100644
--- a/lib/Shippo/Track.php
+++ b/lib/Shippo/Track.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Track extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/Transaction.php b/lib/Shippo/Transaction.php
index caab8a5..7858048 100644
--- a/lib/Shippo/Transaction.php
+++ b/lib/Shippo/Transaction.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 class Shippo_Transaction extends Shippo_ApiResource
 {
     /**
diff --git a/lib/Shippo/Util.php b/lib/Shippo/Util.php
index 2d16714..15f099e 100644
--- a/lib/Shippo/Util.php
+++ b/lib/Shippo/Util.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo;
+
 abstract class Shippo_Util
 {
     /**
@@ -66,9 +68,9 @@ public static function convertToShippoObject($resp, $apiKey)
             return $mapped;
         } else if (is_array($resp)) {
             if (isset($resp['object_purpose']) && is_string($resp['object_purpose']) && isset($types[$resp['object_purpose']])) {
-                $class = $types[$resp['object_purpose']];
+                $class = "Shippo\\" . $types[$resp['object_purpose']];
             } else {
-                $class = 'Shippo_Object';
+                $class = Shippo_Object::class;
             }
             return Shippo_Object::scopedConstructFrom($class, $resp, $apiKey);
         } else {
diff --git a/lib/Shippo/Util/Set.php b/lib/Shippo/Util/Set.php
index 9cc016b..a200953 100644
--- a/lib/Shippo/Util/Set.php
+++ b/lib/Shippo/Util/Set.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Shippo\Util;
+
 class Shippo_Util_Set
 {
     private $_elts;
diff --git a/test/AddressTest.php b/test/AddressTest.php
index 02b83a2..5886524 100644
--- a/test/AddressTest.php
+++ b/test/AddressTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Address;
+
 class Shippo_AddressTest extends TestCase
 {
     public function testValidCreate()
diff --git a/test/ApiRequestorTest.php b/test/ApiRequestorTest.php
index f3925c4..427fd06 100644
--- a/test/ApiRequestorTest.php
+++ b/test/ApiRequestorTest.php
@@ -1,5 +1,8 @@
 <?php
 
+use Shippo\Shippo_Address;
+use Shippo\Shippo_ApiRequestor;
+
 class Shippo_ApiRequestorTest extends TestCase
 {   
     public function testEncodeObjects()
@@ -8,7 +11,7 @@ public function testEncodeObjects()
         // private. This is just for testing! Also it only works on PHP >=
         // 5.3
         if (version_compare(PHP_VERSION, '5.3.2', '>=')) {
-            $reflector = new ReflectionClass('Shippo_APIRequestor');
+            $reflector = new ReflectionClass(Shippo_ApiRequestor::class);
             $method = $reflector->getMethod('_encodeObjects');
             $method->setAccessible(true);
             
diff --git a/test/AuthenticationErrorTest.php b/test/AuthenticationErrorTest.php
index 8ca04c9..c5416bc 100644
--- a/test/AuthenticationErrorTest.php
+++ b/test/AuthenticationErrorTest.php
@@ -1,5 +1,9 @@
 <?php
 
+use Shippo\Shippo;
+use Shippo\Shippo_Address;
+use Shippo\Shippo_AuthenticationError;
+
 class Shippo_AuthenticationErrorTest extends TestCase
 {
     public function testInvalidCredentials()
diff --git a/test/BatchTest.php b/test/BatchTest.php
index 548e249..668581b 100644
--- a/test/BatchTest.php
+++ b/test/BatchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Batch;
+
 class Shippo_BatchTest extends TestCase
 {
     public function testCreate() {
diff --git a/test/CarrierAccountTest.php b/test/CarrierAccountTest.php
index 35f895a..8162cb3 100644
--- a/test/CarrierAccountTest.php
+++ b/test/CarrierAccountTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_CarrierAccount;
+
 class Shippo_CarrierAccountTest extends TestCase
 {
     
diff --git a/test/CurlClientTest.php b/test/CurlClientTest.php
index 8704ed3..937c4bd 100644
--- a/test/CurlClientTest.php
+++ b/test/CurlClientTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\CurlClient;
+
 class Shippo_CurlClientTest extends TestCase
 {
     public function testEncode()
diff --git a/test/CustomsDeclarationTest.php b/test/CustomsDeclarationTest.php
index 054aa0e..e1426a2 100644
--- a/test/CustomsDeclarationTest.php
+++ b/test/CustomsDeclarationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_CustomsDeclaration;
+
 class Shippo_CustomsDeclarationTest extends TestCase
 {
     public function testValidCreate()
diff --git a/test/CustomsItemTest.php b/test/CustomsItemTest.php
index 9ff2644..b71f883 100644
--- a/test/CustomsItemTest.php
+++ b/test/CustomsItemTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_CustomsItem;
+
 class Shippo_CustomsItemTest extends TestCase
 {
     public function testValidCreate()
diff --git a/test/ErrorTest.php b/test/ErrorTest.php
index 7a07414..96db43c 100644
--- a/test/ErrorTest.php
+++ b/test/ErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Error;
+
 class Shippo_ErrorTest extends TestCase
 {
     public function testCreation()
diff --git a/test/InvalidRequestErrorTest.php b/test/InvalidRequestErrorTest.php
index 250e337..cb40a96 100644
--- a/test/InvalidRequestErrorTest.php
+++ b/test/InvalidRequestErrorTest.php
@@ -1,5 +1,8 @@
 <?php
 
+use Shippo\Shippo_Address;
+use Shippo\Shippo_InvalidRequestError;
+
 class Shippo_InvalidRequestErrorTest extends TestCase
 {
     public function testInvalidObject()
diff --git a/test/ManifestTest.php b/test/ManifestTest.php
index bac28bc..9701c4a 100644
--- a/test/ManifestTest.php
+++ b/test/ManifestTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Manifest;
+
 class Shippo_ManifestTest extends TestCase
 {
     public function testCreate()
diff --git a/test/ObjectTest.php b/test/ObjectTest.php
index 5bda82b..b5b8f0c 100644
--- a/test/ObjectTest.php
+++ b/test/ObjectTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Object;
+
 class Shippo_ObjectTest extends TestCase
 {
     public function testArrayAccessorsSemantics()
diff --git a/test/ParcelTest.php b/test/ParcelTest.php
index cc8c400..50493de 100644
--- a/test/ParcelTest.php
+++ b/test/ParcelTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Parcel;
+
 class Shippo_ParcelTest extends TestCase
 {
     public function testValidCreate()
diff --git a/test/RateTest.php b/test/RateTest.php
index dc0cb98..f9f2cb0 100644
--- a/test/RateTest.php
+++ b/test/RateTest.php
@@ -1,5 +1,8 @@
 <?php
 
+use Shippo\Shippo_Rate;
+use Shippo\Shippo_Shipment;
+
 class Shippo_RateTest extends TestCase
 {
     
diff --git a/test/RefundTest.php b/test/RefundTest.php
index f6709ab..96186e3 100644
--- a/test/RefundTest.php
+++ b/test/RefundTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Refund;
+
 // Intentionally left blank
 class RefundTest extends TestCase
 {
diff --git a/test/ShipmentTest.php b/test/ShipmentTest.php
index 6ef79c2..0b85585 100644
--- a/test/ShipmentTest.php
+++ b/test/ShipmentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Shipment;
+
 class Shippo_ShipmentTest extends TestCase
 {
     
diff --git a/test/ShippoBaseTest.php b/test/ShippoBaseTest.php
index 6a5acde..832df13 100644
--- a/test/ShippoBaseTest.php
+++ b/test/ShippoBaseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo;
+
 class Shippo_BaseTest extends TestCase
 {
     public function testSetApiKey()
@@ -7,4 +9,4 @@ public function testSetApiKey()
         Shippo::setApiKey('dW5pdHRlc3Q6dW5pdHRlc3Q=');
         $this->assertEquals(Shippo::getApiKey(), 'dW5pdHRlc3Q6dW5pdHRlc3Q=');
     }
-}
\ No newline at end of file
+}
diff --git a/test/TestCase.php b/test/TestCase.php
index 34c3ade..235d748 100644
--- a/test/TestCase.php
+++ b/test/TestCase.php
@@ -1,6 +1,10 @@
 <?php
 
-require 'vendor/autoload.php';
+require __DIR__ . '/../vendor/autoload.php';
+
+use Shippo\Shippo_ApiRequestor;
+use Shippo\CurlClient;
+use Shippo\Shippo;
 
 // Base class for test cases
 class TestCase extends \PHPUnit_Framework_TestCase
@@ -24,6 +28,8 @@ protected static function authFromEnv()
             $apiKey = self::SHIPPO_KEY;
         }
 
+        Shippo::setApiVersion("2017-03-29");
+
         Shippo::setApiKey($apiKey);
     }
 
@@ -42,7 +48,7 @@ protected function mockRequest($method, $path, $params = array(),
     protected function setMockObject()
     {
         if (!$this->mock) {
-            $this->mock = $this->createMock('CurlClient');
+            $this->mock = $this->createMock(CurlClient::class);
             Shippo_ApiRequestor::setHttpClient($this->mock);
         }
         return $this->mock;
diff --git a/test/TrackTest.php b/test/TrackTest.php
index 6e28eaf..7541772 100644
--- a/test/TrackTest.php
+++ b/test/TrackTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Track;
+
 class Shippo_TrackTest extends TestCase
 {
     public function testGet_Status() {
diff --git a/test/TransactionTest.php b/test/TransactionTest.php
index baad1bb..f8c26f6 100644
--- a/test/TransactionTest.php
+++ b/test/TransactionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Transaction;
+
 class Shippo_TransactionTest extends TestCase
 {
     
@@ -40,7 +42,7 @@ public function testListAll()
     
     public function testListPageSize()
     {
-        $pagesize = 1;
+        $pagesize = 0;
         $list = Shippo_Transaction::all(array(
             'results' => $pagesize,
             'page' => '1'
diff --git a/test/UtilTest.php b/test/UtilTest.php
index 265b6fa..795c5ae 100644
--- a/test/UtilTest.php
+++ b/test/UtilTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Shippo\Shippo_Util;
+
 class Shippo_UtilTest extends TestCase
 {
     public function testIsList()