Use new poll util to get exchange rate

Author: tanx

src/action/wallet.js

@@ -309,9 +309,7 @@ class WalletAction {
    * @return {Promise<undefined>}
    */
   async pollExchangeRate() {
-    await this.getExchangeRate();
-    clearTimeout(this.tPollRate);
-    this.tPollRate = setTimeout(() => this.pollExchangeRate(), RATE_DELAY);
+    await poll(() => this.getExchangeRate(), RATE_DELAY);
   }
 
   /**

test/unit/action/wallet.spec.js

@@ -5,7 +5,6 @@ import WalletAction from '../../../src/action/wallet';
 import NavAction from '../../../src/action/nav';
 import NotificationAction from '../../../src/action/notification';
 import * as logger from '../../../src/action/log';
-import { nap } from '../../../src/helper';
 import nock from 'nock';
 import 'isomorphic-fetch';
 
@@ -33,7 +32,6 @@ describe('Action Wallet Unit Tests', () => {
   });
 
   afterEach(() => {
-    clearTimeout(wallet.tPollRate);
     sandbox.restore();
   });
 
@@ -357,11 +355,11 @@ describe('Action Wallet Unit Tests', () => {
   });
 
   describe('pollExchangeRate()', () => {
-    it('should call getExchangeRate', async () => {
+    it('should poll getExchangeRate', async () => {
       sandbox.stub(wallet, 'getExchangeRate');
+      wallet.getExchangeRate.onSecondCall().resolves(true);
       await wallet.pollExchangeRate();
-      await nap(30);
-      expect(wallet.getExchangeRate.callCount, 'to be greater than', 1);
+      expect(wallet.getExchangeRate, 'was called twice');
     });
   });