### Question:
CommandHelper { public static Class<?> getCommandClass(String commandName){ if (hasCommand(commandName)){ return ExtensionLoader.getExtensionLoader(BaseCommand.class).getExtension(commandName).getClass(); }else { return null; } }  static boolean hasCommand(String commandName); static List<Class<?>> getAllCommandClass(); static Class<?> getCommandClass(String commandName);  }### Answer:
@Test public void testGetCommandClass() throws Exception { assertThat(CommandHelper.getCommandClass("greeting"), equalTo(GreetingCommand.class)); assertNull(CommandHelper.getCommandClass("not-exiting")); }