### Question:
CommandHelper { public static boolean hasCommand(String commandName) { BaseCommand command = null; try { command = ExtensionLoader.getExtensionLoader(BaseCommand.class).getExtension(commandName); } catch (Throwable throwable) { return false; } return command != null; }  static boolean hasCommand(String commandName); static List<Class<?>> getAllCommandClass(); static Class<?> getCommandClass(String commandName);  }### Answer:
@Test public void testHasCommand() throws Exception { assertTrue(CommandHelper.hasCommand("greeting")); assertFalse(CommandHelper.hasCommand("not-exiting")); }