Support PHPUnit 6

tests/Spout/Common/Entity/Style/BorderTest.php

@@ -6,11 +6,12 @@ use Box\Spout\Writer\Common\Creator\Style\BorderBuilder;
 use Box\Spout\Writer\Exception\Border\InvalidNameException;
 use Box\Spout\Writer\Exception\Border\InvalidStyleException;
 use Box\Spout\Writer\Exception\Border\InvalidWidthException;
+use PHPUnit\Framework\TestCase;
 
 /**
  * Class BorderTest
  */
-class BorderTest extends \PHPUnit_Framework_TestCase
+class BorderTest extends TestCase
 {
     /**
      * @return void

tests/Spout/Common/Entity/Style/ColorTest.php

@@ -3,11 +3,12 @@
 namespace Box\Spout\Common\Entity\Style;
 
 use Box\Spout\Common\Exception\InvalidColorException;
+use PHPUnit\Framework\TestCase;
 
 /**
  * Class ColorTest
  */
-class ColorTest extends \PHPUnit_Framework_TestCase
+class ColorTest extends TestCase
 {
     /**
      * @return array