public void add(Plugin plugin)
	{
		plugins.add(plugin);
	}
@Test
	public void ensureNoDuplicateConfigKeyNames()
	{
		for (final Class<?> clazz : configClasses)
		{
			final Set<String> configKeyNames = new HashSet<>();

			for (final Method method : clazz.getMethods())
			{
				if (!method.isDefault())
				{
					continue;
				}

				final ConfigItem annotation = method.getAnnotation(ConfigItem.class);

				if (annotation == null)
				{
					continue;
				}

				final String configKeyName = annotation.keyName();

				if (configKeyNames.contains(configKeyName))
				{
					throw new IllegalArgumentException("keyName " + configKeyName + " is duplicated in " + clazz);
				}

				configKeyNames.add(configKeyName);
			}
		}
	}