[Improvement] Optimize demo test (#1053)

packages/list/test/__snapshots__/demo.spec.js.snap

@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`renders list correctly 1`] = `
+exports[`renders demo correctly 1`] = `
 <div>
   <div>
     <p class="page-desc">当即将滚动到元素底部时，会自动加载更多</p>

packages/list/test/demo.spec.js

@@ -1,4 +1,4 @@
-import List from '../';
+import Demo from '../demo';
 import demoTest from '../../../test/demo-test';
 
-demoTest(List);
+demoTest(Demo);