python - pytest`AssertionError: View function mapping is overwritten an existing endpoint function:`flask-restful while registring blueprint

Question

问题如下，我创建了一个虚拟示例。文件夹结构在哪里：

.
├── api_bp
│   └── __init__.py
├── app.py
├── pytest.ini
└── tests
    ├── conftest.py
    ├── __init__.py
    ├── test_todo1.py
    └── test_todo2.py

文件夹api_bp里面的代码__init__.py：

# __init__.py

from flask import Blueprint

api_bp = Blueprint('api', __name__)

烧瓶应用程序：

# app.py

from flask import Flask, Blueprint
from flask_restful import Api, Resource


class TodoItem(Resource):
    def get(self, id):
        return {'task': 'Say "Hello, World!"'}


def create_app():
    """Initialize the app. """
    app = Flask(__name__)
    from api_bp import api_bp
    # api_bp = Blueprint('api', __name__)
    api = Api(api_bp)

    api.add_resource(TodoItem, '/todos/<int:id>')
    app.register_blueprint(api_bp, url_prefix='/api')

    return app


if __name__ == '__main__':
    app = create_app()
    app.run(debug=True)

出于测试目的，我为不同的待办事项提供了客户端夹具和两个测试（我故意将它们放入单独的模块中）：

# conftest.py

import pytest

from app_factory import create_app

@pytest.fixture(scope='module')
def client():
    flask_app = create_app()

    testing_client = flask_app.test_client()

    context = flask_app.app_context()
    context.push()

    yield testing_client

    context.pop()

# test_todo1.py

import pytest

def test_todo2(client):
    """Test"""
    response = client.get('/api/todos/1')
    print(response)
    assert response.status_code == 200

# test_todo2.py

import pytest

def test_todo2(client):
    """Test"""
    response = client.get('/api/todos/2')
    print(response)
    assert response.status_code == 200

因此，当我运行$ pytest -v测试它时，我最终会遇到以下错误：

AssertionError: View function mapping is overwriting an existing endpoint function: api.todoitem

这是因为注册了蓝图。我想了解烧瓶 (flask-restful) 与 pytest 相结合的神奇之处。因为如果我像这样定义我的app.py模块，它会成功通过测试：

# app.py

from flask import Flask, Blueprint
from flask_restful import Api, Resource


class TodoItem(Resource):
    def get(self, id):
        return {'task': 'Say "Hello, World!"'}


def create_app():
    """Initialize the app. """
    app = Flask(__name__)
    # note: I commented the line below and defined the blueprint in-place
    # from api_bp import api_bp  
    api_bp = Blueprint('api', __name__)
    api = Api(api_bp)

    api.add_resource(TodoItem, '/todos/<int:id>')
    app.register_blueprint(api_bp, url_prefix='/api')

    return app


if __name__ == '__main__':
    app = create_app()
    app.run(debug=True)

$ pytest -v
tests/test_api1.py::test_todo2 PASSED    [ 50%]
tests/test_api2.py::test_todo2 PASSED    [100%]

或者，如果我不使用应用程序工厂，它也可以正常工作：

# app.py

from flask import Flask, Blueprint
from flask_restful import Api, Resource

app = Flask(__name__)
api_bp = Blueprint('api', __name__)
api = Api(api_bp)


class TodoItem(Resource):
    def get(self, id):
        return {'task': 'Say "Hello, World!"'}


api.add_resource(TodoItem, '/todos/<int:id>')
app.register_blueprint(api_bp, url_prefix='/api')

如果我将所有测试都放在一个模块中，或者我先注册蓝图然后添加如下资源，也可以修复它：

# app.py

...

def create_app():
    """Initialize the app. """
    app = Flask(__name__)

    from api_bp import api_bp

    api = Api(api_bp)

    app.register_blueprint(api_bp, url_prefix='/api')
    api.add_resource(TodoItem, '/todos/<int:id>')


    return app

...

谁知道这里发生了什么并能解释一下magic？提前致谢。

标签： pythonflaskpytestflask-restful

Answer 1

因此，问题的解释是，当 pytest 设置并在测试中使用客户端时，它会运行create_app()并在未在内部定义蓝图时尝试重用蓝图app.py：

tests/test_api1.py::test_todo2 <flask.blueprints.Blueprint object at 0x7f04a8c9c610>

    SETUP    M client
        tests/test_api1.py::test_todo2 (fixtures used: client)<Response streamed [200 OK]>
PASSED
    TEARDOWN M client
tests/test_api2.py::test_todo2 <flask.blueprints.Blueprint object at 0x7f04a8c9c610>

    SETUP    M clientERROR
    TEARDOWN M client

它可以通过这样做来修复：

# api_bp/__init__.py

from flask import Blueprint


get_blueprint = lambda: Blueprint('api', __name__)

并使用：

def create_app():
    """Initialize the app. """
    app = Flask(__name__)
    from api_bp import get_blueprint

    api_bp = get_blueprint()
    api = Api(api_bp)

    api.add_resource(TodoItem, '/todos/<int:id>')
    app.register_blueprint(api_bp, url_prefix='/api')

    return app

因此，此类问题的最简单解决方案是使用适当的 pytest 范围（不是“模块”）：

@pytest.fixture(scope='session')
def client():
...

更新：

这种方法不适用于定义管理命令，例如：

class Test(Command):
    def run(self):
        """Runs the tests."""
        pytest.main(['-s', '-v', './tests'])


manager.add_command('test', Test)  # run the tests

使用python app.py test您将得到与前面示例中相同的错误。有关更多详细信息，请阅读以下链接中的“注意：”部分：https ://docs.pytest.org/en/latest/usage.html#calling-pytest-from-python-code