Flask route parameters - default values

from flask import Flask
app = Flask(__name__)

@app.get("/")
def main_page():
    return '''
Main<br>
<a href="/user/23">23</a><br>
<a href="/user/42">42</a><br>
<a href="/user/Joe">Joe</a><br>
'''

@app.get("/user/", defaults={ 'uid': 'zero' })
@app.get("/user/<uid>")
def user_by_uid(uid):
    if uid == 'zero':
        return "List users"
    return uid

import pytest
import path_default

@pytest.fixture()
def web():
    return path_default.app.test_client()

def test_main_page(web):
    rv = web.get('/')
    assert rv.status == '200 OK'
    assert b'Main<br>' in rv.data

@pytest.mark.parametrize('uid', ['23', '42', 'Joe'])
def test_user(web, uid):
    rv = web.get(f'/user/{uid}')
    assert rv.status == '200 OK'
    assert uid == rv.data.decode('utf-8')

def test_user_root_slash(web):
    rv = web.get(f'/user/')
    assert rv.status == '200 OK'
    assert b'List users' == rv.data

def test_user_root(web):
    rv = web.get(f'/user')
    assert rv.status == '308 PERMANENT REDIRECT'
    assert rv.headers['Location'] == 'http://localhost/user/'
    assert b'<p>You should be redirected automatically to the target URL:' in rv.data