fix: tests for components

__tests__/unit/app/components/Header.jsx

@@ -0,0 +1,12 @@
+import React from 'react'
+import { shallow } from 'enzyme'
+import Header from 'app/components/Header.jsx'
+
+describe('app/components/Header.jsx', () => {
+  it('renders Header component', () => {
+    expect(Header).toBeDefined()
+    const tree = shallow(<Header />)
+    expect(tree.find('Page')).toBeDefined()
+    expect(tree.text()).toContain('Stream things!')
+  })
+})

__tests__/unit/app/components/Page.jsx

@@ -0,0 +1,11 @@
+import React from 'react'
+import { shallow } from 'enzyme'
+import Page from 'app/components/Page.jsx'
+
+describe('app/components/Page.jsx', () => {
+  it('renders Page component', () => {
+    expect(Page).toBeDefined()
+    const tree = shallow(<Page />)
+    expect(tree).toBeDefined()
+  })
+})