Update test cases

Signed-off-by: Riyadh Al Nur <riyadhalnur@verticalaxisbd.com>

tests/tests.js

@@ -1,15 +1,16 @@
 'use strict';
 
 const chai = require('chai');
-chai.should();
-
+const chaiAsPromised = require('chai-as-promised');
 const weather = require('../index.js');
 
+chai.use(chaiAsPromised);
+chai.should();
+
 describe('Weather', () => {
-	it('should get the weather', (done) => {
-		weather([], (err, result) => {
-			result.should.exist;
-			done();
-		});
-	});
+  it('should get the weather', () => {
+    return weather([]).should.be.fulfilled.then(res => {
+      res.data.should.be.an.instanceOf(Object);
+    });
+  });
 });