NoticeBar: improve test coverage

test/unit/components/notice-bar.vue

@@ -0,0 +1,16 @@
+<template>
+  <div class="notice-bar-container" style="width: 100px;">
+    <van-notice-bar :speed="speed" :text="text" :mode="mode" :delay="delay" />
+  </div>
+</template>
+
+<script>
+import NoticeBar from 'packages/notice-bar';
+export default {
+  components: {
+    [NoticeBar.name]: NoticeBar
+  },
+  props: ['speed', 'text', 'mode', 'delay']
+};
+</script>
+