Add some testing

By: Erik Broes <erikbroes@grum.nl>

paper-server/src/test/java/org/bukkit/AchievementTest.java

@@ -0,0 +1,41 @@
+package org.bukkit;
+
+import static org.hamcrest.Matchers.hasSize;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThat;
+
+import java.util.List;
+
+import net.minecraft.server.Statistic;
+import net.minecraft.server.StatisticList;
+
+import org.bukkit.support.Util;
+import org.junit.Test;
+
+import com.google.common.collect.Lists;
+
+public class AchievementTest {
+    @Test
+    @SuppressWarnings("unchecked")
+    public void verifyMapping() throws IllegalArgumentException, SecurityException, IllegalAccessException, NoSuchFieldException {
+        List<Achievement> achievements = Lists.newArrayList(Achievement.values());
+
+        for (Statistic statistic : (List<Statistic>) StatisticList.b) {
+            int id = statistic.e;
+            String hash = statistic.g;
+
+            if ((id & Achievement.STATISTIC_OFFSET) != Achievement.STATISTIC_OFFSET) continue;
+            if (hash == null) continue;
+
+            String name = Util.getInternalState(Statistic.class, statistic, "a");
+            String message = String.format("org.bukkit.Achievement is missing id: %d named: '%s'", id - Achievement.STATISTIC_OFFSET, name);
+
+            Achievement subject = Achievement.getById(id);
+            assertNotNull(message, subject);
+
+            achievements.remove(subject);
+        }
+
+        assertThat("org.bukkit.Achievement has too many achievements", achievements, hasSize(0));
+    }
+}