Add testcase for toString

Author: O-Link06

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

@@ -0,0 +1,17 @@
+package com.gildedrose;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ItemTest {
+
+    private final Item normalItem = new Item("Foo", 10, 20);
+
+    @DisplayName("toString prints name and quality")
+    @Test
+    void testToString() {
+        assertThat(normalItem.toString()).isEqualTo("Foo, 10, 20");
+    }
+}