一. 测试
Flask提供的测试渠道是Werkzeug的Client来处理本地环境，未经测试的应用难于改进现有的代码。
二. 代码
Flask实现测试的代码存放于flask/testing.py文件中，如下
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# -*- coding: utf-8 -*-
import werkzeug
from contextlib import contextmanager
from werkzeug.test import Client, EnvironBuilder
from flask import _request_ctx_stack
try:
from werkzeug.urls import url_parse
except ImportError:
from urlparse import urlsplit as url_parse
def make_test_environ_builder(app, path='/', base_url=None, *args, **kwargs):
http_host = app.config.get('SERVER_NAME')
app_root = app.config.get('APPLICATION_ROOT')
if base_url is None:
url = url_parse(path)
base_url = 'http://%s/' % (url.netloc or http_host or 'localhost')
if app_root:
base_url += app_root.lstrip('/')
if url.netloc:
path = url.path
if url.query:
path += '?' + url.query
return EnvironBuilder(path, base_url, *args, **kwargs)
class FlaskClient(Client):
preserve_context = False
def __init__(self, *args, **kwargs):
super(FlaskClient, self).__init__(*args, **kwargs)
self.environ_base = {
"REMOTE_ADDR": "127.0.0.1",
"HTTP_USER_AGENT": "werkzeug/" + werkzeug.__version__
}
@contextmanager
def session_transaction(self, *args, **kwargs):
if self.cookie_jar is None:
raise RuntimeError('Session transactions only make sense '
'with cookies enabled.')
app = self.application
environ_overrides = kwargs.setdefault('environ_overrides', {})
self.cookie_jar.inject_wsgi(environ_overrides)
outer_reqctx = _request_ctx_stack.top
with app.test_request_context(*args, **kwargs) as c:
sess = app.open_session(c.request)
if sess is None:
raise RuntimeError('Session backend did not open a session. '
'Check the configuration')
_request_ctx_stack.push(outer_reqctx)
try:
yield sess
finally:
_request_ctx_stack.pop()
resp = app.response_class()
if not app.session_interface.is_null_session(sess):
app.save_session(sess, resp)
headers = resp.get_wsgi_headers(c.request.environ)
self.cookie_jar.extract_wsgi(c.request.environ, headers)
def open(self, *args, **kwargs):
kwargs.setdefault('environ_overrides', {}) \
['flask._preserve_context'] = self.preserve_context
kwargs.setdefault('environ_base', self.environ_base)
as_tuple = kwargs.pop('as_tuple', False)
buffered = kwargs.pop('buffered', False)
follow_redirects = kwargs.pop('follow_redirects', False)
builder = make_test_environ_builder(self.application, *args, **kwargs)
return Client.open(self, builder,
as_tuple=as_tuple,
buffered=buffered,
follow_redirects=follow_redirects)
def __enter__(self):
if self.preserve_context:
raise RuntimeError('Cannot nest client invocations')
self.preserve_context = True
return self
def __exit__(self, exc_type, exc_value, tb):
self.preserve_context = False
top = _request_ctx_stack.top
if top is not None and top.preserved:
top.pop()
三. 解析
先来看看flask/app.py，里面有个调用到测试模块，如下
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class Flask(_PackageBoundObject):
test_client_class = None
def test_client(self, use_cookies=True, **kwargs):
cls = self.test_client_class
if cls is None:
from flask.testing import FlaskClient as cls
return cls(self, self.response_class, use_cookies=use_cookies, **kwargs)
这段代码是导入测试模块，为程序提供一个测试客户端的入口。 接下来具体看看FlaskClient类是怎么提供测试客户端入口的支持的。
- FlaskClient类使用了魔术方法__enter__和__exit__实现了上下文管理协议，当使用with关键字调用FlaskClient类时，如果当前的flask程序已经有另外的测试实例在运行，触发__enter__则报错退出，如果只有当前测试实例，退出时把测试环境创建的上下文的最新堆栈数据清空。
- session_transaction方法是contextmanager装饰器来装饰的，contextmanager其实也是上下文管理协议，
- 如果当前测试用例环境下的cookies为空，则抛出异常
- 模拟客户端调用，从而在测试客户端的上下文中打开一个Session，在事务结束时，抛出当前的模拟数据，Session将恢复到原来的值
- open函数是基于flask程序的配置和werkzeug.test的Client类和EnvironBuilder类，从而创建一个虚拟的客户端请求对象
四. 使用
应用使用可以参考测试 Flask 应用
