Minor householding in tests

- Add missing test for injector
- Remove redundant Mock fields

src/test/java/fr/xephi/authme/util/StringUtilsTest.java

@@ -1,5 +1,6 @@
 package fr.xephi.authme.util;
 
+import fr.xephi.authme.TestHelper;
 import org.junit.Test;
 
 import java.io.File;
@@ -145,4 +146,9 @@ public class StringUtilsTest {
         // then
         assertThat(result, equalTo("path" + File.separator + "to" + File.separator + "test-file.txt"));
     }
+
+    @Test
+    public void shouldHaveHiddenConstructor() {
+        TestHelper.validateHasOnlyPrivateEmptyConstructor(StringUtils.class);
+    }
 }

src/test/java/fr/xephi/authme/util/TeleportationServiceTest.java

@@ -5,7 +5,6 @@ import fr.xephi.authme.cache.auth.PlayerCache;
 import fr.xephi.authme.cache.limbo.LimboPlayer;
 import fr.xephi.authme.events.FirstSpawnTeleportEvent;
 import fr.xephi.authme.events.SpawnTeleportEvent;
-import fr.xephi.authme.output.Messages;
 import fr.xephi.authme.settings.NewSetting;
 import fr.xephi.authme.settings.SpawnLoader;
 import fr.xephi.authme.settings.properties.RestrictionSettings;
@@ -48,9 +47,6 @@ public class TeleportationServiceTest {
     @Mock
     private NewSetting settings;
 
-    @Mock
-    private Messages messages;
-
     @Mock
     private BukkitService bukkitService;