add test and clean code

Author: leibale

packages/client/lib/commands/CLUSTER_MYSHARDID.spec.ts

@@ -1,5 +1,5 @@
 import { strict as assert } from 'assert';
-import testUtils from '../test-utils';
+import testUtils, { GLOBAL } from '../test-utils';
 import { transformArguments } from './CLUSTER_MYSHARDID';
 
 describe('CLUSTER MYSHARDID', () => {
@@ -11,4 +11,12 @@ describe('CLUSTER MYSHARDID', () => {
             ['CLUSTER', 'MYSHARDID']
         );
     });
+
+    testUtils.testWithCluster('clusterNode.clusterMyShardId', async cluster => {
+        const client = await cluster.nodeClient(cluster.masters[0]);
+        assert.equal(
+            typeof await client.clusterMyShardId(),
+            'string'
+        );
+    }, GLOBAL.CLUSTERS.OPEN);
 });

packages/client/lib/commands/CLUSTER_MYSHARDID.ts

@@ -1,9 +1,7 @@
-import { RedisCommandArgument, RedisCommandArguments } from '.';
+export const IS_READ_ONLY = true;
 
-export function transformArguments(): RedisCommandArguments {
-    const args: RedisCommandArguments = ['CLUSTER', 'MYSHARDID'];
-
-    return args;
+export function transformArguments() {
+    return ['CLUSTER', 'MYSHARDID'];
 }
 
-export declare function transformReply(): RedisCommandArgument;
+export declare function transformReply(): string | Buffer;