migrate to JUnit 5

Java/src/test/java/com/gildedrose/GildedRoseTest.java

@@ -1,13 +1,13 @@
 package com.gildedrose;
 
-import static org.junit.Assert.*;
+import org.junit.jupiter.api.Test;
 
-import org.junit.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
-public class GildedRoseTest {
+class GildedRoseTest {
 
     @Test
-    public void foo() {
+    void foo() {
         Item[] items = new Item[] { new Item("foo", 0, 0) };
         GildedRose app = new GildedRose(items);
         app.updateQuality();