Pytest: Flask app sending mail

This is a web application that allows the user to register by providing an email. The system then generates a unique code and sends an email to the registered address with a link back to the server.

The user is expected to click on the link in the email to verify that it is indeed his email address and he wanted to subscribe.

from flask import Flask, request
import random

app = Flask(__name__)
db = {}

@app.route('/', methods=['GET'])
def home():
    return '''
          <form method="POST" action="/register">
          <input name="email">
          <input type="submit">
          </form>
          '''

@app.route('/register', methods=['POST'])
def register():
    email = request.form.get('email')
    code = str(random.random())
    if db_save(email, code):
        html = '<a href="/verify/{email}/{code}">here</a>'.format(email=email, code = code)
        sendmail({'to': email, 'subject': 'Registration', 'html': html })
        return 'OK'
    else:
        return 'FAILED'

@app.route('/verify/<email>/<code>', methods=['GET'])
def verify(email, code):
    if db_verify(email, code):
        sendmail({'to': email, 'subject': 'Welcome!', 'html': '' })
        return 'OK'
    else:
        return 'FAILED'

def sendmail(data):
    pass

def db_save(email, code):
   if email in db:
       return False
   db[email] = code
   return True

def db_verify(email, code):
    return email in db and db[email] == code