1、前言#####
最近在學習django仇味，使用的書是《Python Web開發(fā) 測試驅動方法》硫惕，在第四章中遇到了一個問題使用render_to_string()函數(shù)。學習過程中使用的是py2敞斋，Django的版本是1.10.1截汪。
2、問題描述#####
第四章的單元測試部分代碼：
class HomePageTest(TestCase):
[...]
def test_home_page_returns_correct_html(self):
request = HttpRequest()
response = home_page(request)
expected_html = render_to_string('home.html'）
self.assertEqual(response.content.decode(), expected_html)
[...]
在沒有在表單中加入CSRF令牌{% csrf_token %}時植捎，運行都是正常的衙解。
I:\Django_learn\superlists>python manage.py test
Creating test database for alias 'default'...
...
----------------------------------------------------------------------
Ran 3 tests in 0.000s
OK
Destroying test database for alias 'default'...
I:\Django_learn\superlists>
現(xiàn)在在home.html中加入CSRF令牌{% csrf_token %}后。
<html>
<head>
<title>To-Do lists</title>
</head>
<body>
<h1>Your To-Do lists</h1>
<form method="POST">
<input name="item_text" id="id_new_item" placeholder="Enter a to-do item"/>
{% csrf_token %}
</form>
<table id="id_list_table">
<tr><td>{{ new_item_text }}</td></tr>
</table>
</body>
</html>
再次運行單元測試
I:\Django_learn\superlists>python manage.py test
Creating test database for alias 'default'...
.F.
======================================================================
FAIL: test_home_page_returns_correct_html (lists.tests.HomePageTest)
----------------------------------------------------------------------
Traceback (most recent call last):
File "I:\Django_learn\superlists\lists\tests.py", line 28, in test_home_page_returns_correct_html
self.assertEqual(response.content.decode(), expected_html)
AssertionError: u'<html>\n<head>\n <title>To-Do lists</title>\n</head>\n<body>\n <h1>Your To-Do lists</h1>\n <form method="POST">\n <input name="item_text" id="id_new_item" placeholder="Enter a to-do item"/>\n <input type=\'hidden\' name=\'csrfmiddlewaretoken\' value=\'WkE5AMVHQu5oVmJ6wFSU2KjMvXV6yGYwsB3IJ0Too0QM4xXKVPj6BJ24DBLP600v\' />\n </form>\n <table id="id_list_table">\n <tr><td></td></tr>\n </table>\n</body>\n</html>\n' != u'<html>\n<head>\n <title>To-Do lists</title>\n</head>\n<body>\n <h1>Your To-Do lists</h1>\n <form method="POST">\n <input name="item_text" id="id_new_item" placeholder="Enter a to-do item"/>\n \n </form>\n <table id="id_list_table">\n <tr><td></td></tr>\n </table>\n</body>\n</html>\n'
----------------------------------------------------------------------
Ran 3 tests in 0.047s
FAILED (failures=1)
Destroying test database for alias 'default'...
根據(jù)錯誤信息可以知道在最后的斷言self.assertEqual(response.content.decode(), expected_html)導致測試失敗焰枢。
我們添加兩行用于調試蚓峦，打印出response.content.decode()和expected_html.
print 'response.content.decode()\n', response.content.decode()
print 'expected_html\n', expected_html
I:\Django_learn\superlists>python manage.py test
Creating test database for alias 'default'...
.response.content.decode()
<html>
<head>
<title>To-Do lists</title>
</head>
<body>
<h1>Your To-Do lists</h1>
<form method="POST">
<input name="item_text" id="id_new_item" placeholder="Enter a to-do item"/>
<input type='hidden' name='csrfmiddlewaretoken' value='VUMXA6dNnUT8Y2rAY3nAcQyTMtJKGznXqts0HbPaDWN16b4uiMDkFMWp1EVbC3xu' />
</form>
<table id="id_list_table">
<tr><td></td></tr>
</table>
</body>
</html>
expected_html
<html>
<head>
<title>To-Do lists</title>
</head>
<body>
<h1>Your To-Do lists</h1>
<form method="POST">
<input name="item_text" id="id_new_item" placeholder="Enter a to-do item"/>
</form>
<table id="id_list_table">
<tr><td></td></tr>
</table>
</body>
</html>
..
----------------------------------------------------------------------
Ran 3 tests in 0.031s
OK
Destroying test database for alias 'default'...
I:\Django_learn\superlists>
在渲染模板時，Django 會把這個模板標簽替換成一個<input type="hidden">元素,其值是CSRF 令牌济锄。
從上面的html代碼可以看出暑椰，通過視圖函數(shù)home_page()渲染得到的響應包含csrf轉換的<input>元素，而render_to_string()則未生成該部分荐绝，所以導致測試失敗一汽。
3、如何解決#####
經過google低滩，在stackoverflow找到了解決辦法召夹。
按照stackoverflow上的解決辦法(當前djano==1.10.1)岩喷，我使用expected_html = render_to_string('home.html', request=request)和render_to_string('index.html', context_instance=RequestContext(request))仍然會報錯，于是將自己django版本降低到1.8后使用expected_html = render_to_string('home.html', request=request)监憎，測試通過纱意。
