[new feature] Popup: add duration prop

packages/popup/test/__snapshots__/index.spec.js.snap

@@ -1,3 +1,5 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`duration prop 1`] = `<div class="van-popup van-popup--center" style="transition-duration: 0.5s;" name="van-fade"></div>`;
+
 exports[`reset z-index 1`] = `<div class="van-popup van-popup--center" name="van-fade"></div>`;

packages/popup/test/index.spec.js

@@ -200,3 +200,14 @@ test('click event', () => {
   wrapper.trigger('click');
   expect(wrapper.emitted('click')).toBeTruthy();
 });
+
+test('duration prop', () => {
+  const wrapper = mount(Popup, {
+    propsData: {
+      value: true,
+      duration: 0.5
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});