PageHeader: add page-header component (#15714)

test/unit/specs/page-header.spec.js

@@ -0,0 +1,24 @@
+import { createVue, destroyVM, waitImmediate } from '../util';
+import PageHeader from 'packages/page-header';
+
+describe('PageHeader', () => {
+  let vm;
+  afterEach(() => {
+    destroyVM(vm);
+  });
+
+  it('render well and trigger back event', async() => {
+    vm = createVue(PageHeader, {
+      content: 'content'
+    });
+    expect(vm.$el).to.exist;
+    const spy = sinon.spy();
+    vm.$on('back', spy);
+    vm.$el.querySelector('.el-page-header__left').click();
+
+    await waitImmediate();
+
+    expect(spy.calledOnce).to.be.true;
+  });
+});
+