Flask Jinja template with parameters

from flask import Flask, request, render_template
app = Flask(__name__)

@app.route("/")
def main():
    return render_template('echo.html')

@app.route("/echo", methods=['POST'])
def echo():
    user_text = request.form.get('text', '')
    return render_template('echo.html', text=user_text)

<form action="/echo" method="POST">
<input name="text">
<input type="submit" value="Echo">
</form>

You said: <b>{{ text }}</b>

import app

def test_app():
    web = app.app.test_client()

    rv = web.get('/')
    assert rv.status == '200 OK'
    assert b'<form action="/echo" method="POST">' in rv.data

    rv = web.post('/echo', data={ 'text': 'foo bar' })
    assert rv.status == '200 OK'
    assert b'<form action="/echo" method="POST">' in rv.data
    assert b'You said: <b>foo bar</b>' in rv.data

    rv = web.post('/echo')
    assert rv.status == '200 OK'
    assert b'<form action="/echo" method="POST">' in rv.data
    assert b'You said: <b></b>' in rv.data