Compatibility with PHPUnit 6.x fix

tests/compatibility.php

@@ -3,14 +3,14 @@
  * Ensures compatibility with PHPUnit < 6.x
  */
 
-if (!class_exists('PHPUnit\Framework\Constraint\Constraint') && class_exists('PHPUnit_Framework_Constraint')) {
 namespace PHPUnit\Framework\Constraint {
+    if (!class_exists('PHPUnit\Framework\Constraint\Constraint') && class_exists('PHPUnit_Framework_Constraint')) {
         abstract class Constraint extends \PHPUnit_Framework_Constraint {}
     }
 }
 
-if (!class_exists('PHPUnit\Framework\TestCase') && class_exists('PHPUnit_Framework_TestCase')) {
 namespace PHPUnit\Framework {
+    if (!class_exists('PHPUnit\Framework\TestCase') && class_exists('PHPUnit_Framework_TestCase')) {
         abstract class TestCase extends \PHPUnit_Framework_TestCase {}
     }
 }