Added email templating, and user welcome email

server/mailer.test.js

@@ -0,0 +1,19 @@
+/* eslint-disable flowtype/require-valid-file-annotation */
+import { Mailer } from './mailer';
+
+describe('Mailer', () => {
+  let fakeMailer;
+  let sendMailOutput;
+
+  beforeEach(() => {
+    fakeMailer = new Mailer();
+    fakeMailer.transporter = {
+      sendMail: output => (sendMailOutput = output),
+    };
+  });
+
+  test('#welcome', () => {
+    fakeMailer.welcome('user@example.com');
+    expect(sendMailOutput).toMatchSnapshot();
+  });
+});