测试Flask应用程序时保留多种功能的更改

Question

I'm following a talk on Flask about creating an API. I want to write some tests for it. Upon testing creating a resource does testing deleting the resource in another function work? How do I make the creation of a resource persist to be tested for deletion and editing?

David Baumgold - Prototyping New APIs with Flask - PyCon 2016

The talk shows how to make an API for the names and image urls of puppies.

• you create a puppy at the index page with a POST request
• you get a single puppy with a GET from '/puppy_name'
• you get the list of puppies with a GET from '/'
• you edit a puppy with a PUT from '/puppy_name' (along with the new data of course)
• you delete a puppy with a DELETE from '/puppy_name'

import py.test
import unittest
from requests import get, post, delete, put

localhost = 'http://localhost:5000'

class TestApi(unittest.TestCase):
    def test_list_puppies(self):
        index = get(localhost)
        assert index.status_code == 200

    def test_get_puppy(self):
        puppy1 = get(localhost + '/rover')
        puppy2 = get(localhost + '/spot')
        assert puppy1.status_code == 200 and puppy2.status_code == 200

    def test_create_puppy(self):
        create = post(localhost, data={
            'name': 'lassie', 'image_url': 'lassie_url'})
        assert create.status_code == 201

    @py.test.mark.skip('cannot fix it')
    def test_edit_puppy(self):
        ret = put(localhost + '/lassie',
                  data={'name': 'xxx', 'image_url': 'yyy'})
        assert ret.status_code == 201

    def test_puppy_exits(self):
        lassie = get(localhost + '/lassie').status_code
        assert lassie == 200

    def test_delete_puppy(self):
        ret = delete(localhost + '/lassie')
        assert ret.status_code == 200

@app.route('/', methods=['POST'])
def create_puppy():
    puppy, errors = puppy_schema.load(request.form)
    if errors:
    response = jsonify(errors)
    response.status_code = 400
    return response

    puppy.slug = slugify(puppy.name)

    # create in database
    db.session.add(puppy)
    db.session.commit()

    # return an HTTP response
    response = jsonify( {'message': 'puppy created'} )
    response.status_code = 201
    location = url_for('get_puppy', slug=puppy.slug)
    response.headers['location'] = location

    return response

@app.route('/<slug>', methods=['DELETE'])
def delete_puppy(slug):
    puppy = Puppy.query.filter(Puppy.slug == slug).first_or_404()
    db.session.delete(puppy)
    db.session.commit()

    return jsonify( {'message': '{} deleted'.format(puppy.name)} )

The assert statements in both 'test_edit_puppy' and 'test_puppy_exists' fails. I get a 404 status code instead of 201 and 200.

Answer 1

You're testing the wrong thing. You can persist changes to a database, simply by committing it, when you run a test, but you really don't want to do that.

With unit testing you're testing simple units. With integration testing, which is what you're talking about here, you still want each test to have a specific focus. In this particular case you would want to do something like:

def test_delete_puppy(self):
    create = post(localhost, data={
        'name': 'lassie', 'image_url': 'lassie_url'})        
    lassie = get(localhost + '/lassie')

    # not sure if there's an "assume" method, but I would
    # use that here - the test is not a valid test
    # if you can't create a puppy and retrieve the puppy
    # then there's really no way to delete something that
    # does not exist
    assert create.status_code == 201
    assert lassie.status_code == 200

    ret = delete(localhost + '/lassie')
    assert ret.status_code == 200

    lassie = get(localhost + '/lassie')
    assert lassie.status_code == 404

The focus of this test is to test that deleting a puppy works fine. But you want to setup the puppy in the database as either part of your test or part of the setup of your test. It's the arrange portion of arrange, act, assert . You're arranging the state of the world in its proper order before you actually perform the test. The difference between integration testing and unit testing is that with unit testing you'd be mocking out all the endpoints that you're calling, while with integration tests you're going to actually setup all the data that you need before you run the test portion. Which is what you want to do here.