Support PHPUnit 6

tests/Spout/Reader/CSV/ReaderTest.php

@@ -11,11 +11,12 @@ use Box\Spout\Reader\CSV\Manager\OptionsManager;
 use Box\Spout\Reader\Exception\ReaderNotOpenedException;
 use Box\Spout\Reader\ReaderInterface;
 use Box\Spout\TestUsingResource;
+use PHPUnit\Framework\TestCase;
 
 /**
  * Class ReaderTest
  */
-class ReaderTest extends \PHPUnit_Framework_TestCase
+class ReaderTest extends TestCase
 {
     use TestUsingResource;