Create event consistency test + test code cleanup

src/test/java/fr/xephi/authme/TestHelper.java

@@ -6,6 +6,9 @@ import org.mockito.ArgumentCaptor;
 import org.mockito.Mockito;
 
 import java.io.File;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Modifier;
 import java.net.URL;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -84,9 +87,42 @@ public final class TestHelper {
         runnable.run();
     }
 
+    /**
+     * Assign the necessary fields on ConsoleLogger with mocks.
+     *
+     * @return The logger mock used
+     */
     public static Logger setupLogger() {
         Logger logger = Mockito.mock(Logger.class);
         ConsoleLogger.setLogger(logger);
         return logger;
     }
+
+    /**
+     * Check that a class only has a hidden, zero-argument constructor, preventing the
+     * instantiation of such classes (utility classes). Invokes the hidden constructor
+     * as to register the code coverage.
+     *
+     * @param clazz The class to validate
+     */
+    public static void validateHasOnlyPrivateEmptyConstructor(Class<?> clazz) {
+        Constructor<?>[] constructors = clazz.getDeclaredConstructors();
+        if (constructors.length > 1) {
+            throw new IllegalStateException("Class " + clazz.getSimpleName() + " has more than one constructor");
+        } else if (constructors[0].getParameterTypes().length != 0) {
+            throw new IllegalStateException("Constructor of " + clazz + " does not have empty parameter list");
+        } else if (!Modifier.isPrivate(constructors[0].getModifiers())) {
+            throw new IllegalStateException("Constructor of " + clazz + " is not private");
+        }
+
+        // Ugly hack to get coverage on the private constructors
+        // http://stackoverflow.com/questions/14077842/how-to-test-a-private-constructor-in-java-application
+        try {
+            constructors[0].setAccessible(true);
+            constructors[0].newInstance();
+        } catch (InvocationTargetException | InstantiationException | IllegalAccessException e) {
+            throw new UnsupportedOperationException(e);
+        }
+    }
+
 }