Make tests PHPUnit 6.0 compatible

tests/bootstrap.php

@@ -32,7 +32,7 @@ require __DIR__ . '/../vendor/autoload.php';
 
 // Backward compatibility
 if (!class_exists(TestCase::class)) {
-	class_alias(PHPUnit_Framework_TestCase::class, TestCase::class);
+	class_alias(\PHPUnit\Framework\TestCase::class, TestCase::class);
 }
 
 $dice = new Dice();

tests/datasets/api.fixture.php

@@ -738,4 +738,4 @@ return [
 			'uid'  => 42,
 		],
 	],
-];
+];