[new feature] Tabs: support switch tabs with swipe gestrue in the content (#694)

test/components/tabs.vue

@@ -1,5 +1,12 @@
 <template>
-  <van-tabs :active="active" :duration="duration" @click="handleTabClick" @disabled="handleTabDisabledClick" :sticky="sticky">
+  <van-tabs
+    :active="active"
+    :duration="duration"
+    :sticky="sticky"
+    :swipeable="swipeable"
+    @click="handleTabClick"
+    @disabled="handleTabDisabledClick"
+  >
     <van-tab :title="firstTabTitle" :disabled="firstTabDisabled">内容一</van-tab>
     <van-tab title="选项二">内容二</van-tab>
     <van-tab title="选项三" disabled>内容三</van-tab>
@@ -17,7 +24,8 @@ export default {
     firstTabDisabled: {
       type: Boolean
     },
-    sticky: Boolean
+    sticky: Boolean,
+    swipeable: Boolean
   },
 
   data() {

test/specs/tabs.spec.js

@@ -2,6 +2,7 @@ import Tabs from 'packages/tabs';
 import { mount } from 'avoriaz';
 import TabsTestComponent from '../components/tabs';
 import MoreTabsTestComponent from '../components/more-tabs';
+import { triggerTouch } from '../utils';
 
 describe('Tabs', () => {
   let wrapper;
@@ -114,7 +115,7 @@ describe('Tabs', () => {
     });
   });
 
-  it('sticky', (done) => {
+  it('create a sticky tabs', (done) => {
     wrapper = mount(TabsTestComponent, {
       attachToDocument: true,
       propsData: {
@@ -129,4 +130,34 @@ describe('Tabs', () => {
       done();
     }, 30);
   });
+
+  it('create a swipeable tabs', (done) => {
+    wrapper = mount(TabsTestComponent, {
+      attachToDocument: true,
+      propsData: {
+        swipeable: true
+      }      
+    });
+
+    const tabsContainer = wrapper.find('.van-tabs')[0];
+    const tabContent = wrapper.find('.van-tabs__content')[0];
+
+    expect(tabsContainer.vNode.child.curActive).to.equal(0);
+
+    wrapper.vm.$nextTick(() => {
+      triggerTouch(tabContent, 'touchstart', 0, 0);
+      triggerTouch(tabContent, 'touchmove', -100, 0);
+  
+      setTimeout(() => {
+        expect(tabsContainer.vNode.child.curActive).to.equal(1);
+  
+        triggerTouch(tabContent, 'touchstart', 0, 0);
+        triggerTouch(tabContent, 'touchmove', 100, 0);
+        setTimeout(() => {
+          expect(tabsContainer.vNode.child.curActive).to.equal(0);
+          done();      
+        }, 500);
+      }, 500);
+    })
+  });
 });