Use PHPUnit\Framework\TestCase instead of PHPUnit_Framework_TestCase

tests/PayPal/Test/Common/ArrayUtilTest.php

@@ -2,8 +2,9 @@
 namespace PayPal\Test\Common;
 
 use PayPal\Common\ArrayUtil;
+use PHPUnit\Framework\TestCase;
 
-class ArrayUtilTest extends \PHPUnit_Framework_TestCase
+class ArrayUtilTest extends TestCase
 {
 
     public function testIsAssocArray()

tests/PayPal/Test/Common/FormatConverterTest.php

@@ -10,8 +10,9 @@ use PayPal\Api\Tax;
 use PayPal\Common\PayPalModel;
 use PayPal\Converter\FormatConverter;
 use PayPal\Test\Validation\NumericValidatorTest;
+use PHPUnit\Framework\TestCase;
 
-class FormatConverterTest extends \PHPUnit_Framework_TestCase
+class FormatConverterTest extends TestCase
 {
 
     public static function classMethodListProvider()

tests/PayPal/Test/Common/ModelTest.php

@@ -4,8 +4,9 @@ namespace PayPal\Test\Common;
 use PayPal\Api\Payment;
 use PayPal\Common\PayPalModel;
 use PayPal\Core\PayPalConfigManager;
+use PHPUnit\Framework\TestCase;
 
-class ModelTest extends \PHPUnit_Framework_TestCase
+class ModelTest extends TestCase
 {
 
     public function testSimpleClassConversion()

tests/PayPal/Test/Common/PayPalModelTest.php

@@ -1,6 +1,7 @@
 <?php
 
 use PayPal\Common\PayPalModel;
+use PHPUnit\Framework\TestCase;
 
 class SimpleModelTestClass extends PayPalModel
 {
@@ -145,7 +146,7 @@ class ListModelTestClass extends PayPalModel
  * Test class for PayPalModel.
  *
  */
-class PayPalModelTest extends PHPUnit_Framework_TestCase
+class PayPalModelTest extends TestCase
 {
     /**
      * Sets up the fixture, for example, opens a network connection.

tests/PayPal/Test/Common/UserAgentTest.php

@@ -1,8 +1,9 @@
 <?php
 
 use PayPal\Common\PayPalUserAgent;
+use PHPUnit\Framework\TestCase;
 
-class UserAgentTest extends PHPUnit_Framework_TestCase
+class UserAgentTest extends TestCase
 {
 
     public function testGetValue()