[new feature] add Collapse component (#674)

test/components/collapse.vue

@@ -0,0 +1,21 @@
+<template>
+  <van-collapse v-model="active" :accordion="accordion">
+    <van-collapse-item title="a" name="first">content</van-collapse-item>
+    <van-collapse-item title="b">content</van-collapse-item>
+    <van-collapse-item title="c">content</van-collapse-item>
+  </van-collapse>
+</template>
+
+<script>
+export default {
+  props: {
+    accordion: Boolean
+  },
+
+  data() {
+    return {
+      active: this.accordion ? '' : []
+    };
+  }
+};
+</script>

test/specs/collapse.spec.js

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+import { mount } from 'avoriaz';
+import Collapse from '../components/collapse';
+
+describe('Circle', () => {
+  let wrapper;
+  afterEach(() => {
+    wrapper && wrapper.destroy();
+  });
+
+  it('basic mode', () => {
+    wrapper = mount(Collapse);
+
+    const firstTitle = wrapper.find('.van-collapse-item__title')[0];
+    firstTitle.trigger('click');
+    expect(wrapper.vm.active).to.eql(['first']);
+
+    const secondTitle = wrapper.find('.van-collapse-item__title')[1];
+    secondTitle.trigger('click');
+    expect(wrapper.vm.active).to.eql(['first', 1]);
+
+    firstTitle.trigger('click');
+    expect(wrapper.vm.active).to.eql([1]);
+  });
+
+  it('accordion', () => {
+    wrapper = mount(Collapse, {
+      propsData: {
+        accordion: true
+      }
+    });
+
+    const firstTitle = wrapper.find('.van-collapse-item__title')[0];
+    firstTitle.trigger('click');
+    expect(wrapper.vm.active).to.eql('first');
+
+    const secondTitle = wrapper.find('.van-collapse-item__title')[1];
+    secondTitle.trigger('click');
+    expect(wrapper.vm.active).to.eql(1);
+
+    firstTitle.trigger('click');
+    expect(wrapper.vm.active).to.eql('first');
+
+    firstTitle.trigger('click');
+    expect(wrapper.vm.active).to.eql('');
+  });
+});
+