Django 测试在添加另一个 TestCase 后无法安装夹具答案

【问题标题】：Django tests failing to install a fixture after adding one more TestCaseDjango 测试在添加另一个 TestCase 后无法安装夹具
【发布时间】：2017-07-20 10:43:39
【问题描述】：

我几乎开始怀疑一个 Django 应用程序可以拥有多少个 TestCases 是否有一些限制，所以我需要你的帮助来弄清楚如何避免这个问题并在我的应用程序中使用所有 TestCases 进行功能测试.

我的 Django (v1.10.7) 应用程序有 4 个夹具测试用例，它们运行良好。一旦我添加了带有固定装置的第 5 个测试用例，运行测试和

一起

python3 ./manage.py test myapp

开始导致一个随机的旧测试用例失败：

ERROR: setUpClass (myapp.tests.RandomOldTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/django/db/backends/base/base.py", line 206, in _cursor
    return self.create_cursor()
  File "/usr/lib/python3/dist-packages/django/db/backends/postgresql/base.py", line 211, in create_cursor
    cursor = self.connection.cursor()
psycopg2.InterfaceError: connection already closed

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/django/test/testcases.py", line 1019, in setUpClass
    'database': db_name,
  File "/usr/lib/python3/dist-packages/django/core/management/__init__.py", line 130, in call_command
    return command.execute(*args, **defaults)
  File "/usr/lib/python3/dist-packages/django/core/management/base.py", line 345, in execute
    output = self.handle(*args, **options)
  File "/usr/lib/python3/dist-packages/django/core/management/commands/loaddata.py", line 64, in handle
    self.loaddata(fixture_labels)
  File "/usr/lib/python3/dist-packages/django/core/management/commands/loaddata.py", line 104, in loaddata
    self.load_label(fixture_label)
  File "/usr/lib/python3/dist-packages/django/core/management/commands/loaddata.py", line 167, in load_label
    obj.save(using=self.using)
  File "/usr/lib/python3/dist-packages/django/core/serializers/base.py", line 201, in save
    models.Model.save_base(self.object, using=using, raw=True, **kwargs)
  File "/usr/lib/python3/dist-packages/django/db/models/base.py", line 824, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "/usr/lib/python3/dist-packages/django/db/models/base.py", line 889, in _save_table
    forced_update)
  File "/usr/lib/python3/dist-packages/django/db/models/base.py", line 939, in _do_update
    return filtered._update(values) > 0
  File "/usr/lib/python3/dist-packages/django/db/models/query.py", line 654, in _update
    return query.get_compiler(self.db).execute_sql(CURSOR)
  File "/usr/lib/python3/dist-packages/django/db/models/sql/compiler.py", line 1148, in execute_sql
    cursor = super(SQLUpdateCompiler, self).execute_sql(result_type)
  File "/usr/lib/python3/dist-packages/django/db/models/sql/compiler.py", line 833, in execute_sql
    cursor = self.connection.cursor()
  File "/usr/lib/python3/dist-packages/django/db/backends/base/base.py", line 233, in cursor
    cursor = self.make_cursor(self._cursor())
  File "/usr/lib/python3/dist-packages/django/db/backends/base/base.py", line 206, in _cursor
    return self.create_cursor()
  File "/usr/lib/python3/dist-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/lib/python3/dist-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/usr/lib/python3/dist-packages/django/db/backends/base/base.py", line 206, in _cursor
    return self.create_cursor()
  File "/usr/lib/python3/dist-packages/django/db/backends/postgresql/base.py", line 211, in create_cursor
    cursor = self.connection.cursor()
django.db.utils.InterfaceError: Problem installing fixture '/home/lynoure/PycharmProjects/usertools2/useraccounts/fixtures/test-fixtures.json': connection already closed

新的 TestCase 是什么似乎并不重要，即使我用新名称复制了一个预先存在的测试，也会发生这种情况。

如果重要的话，这是在 Debian Stable 上，postgresql 的版本是 9.6+181，python3-psycopg2 是 2.6.2-1。

【问题讨论】：

似乎很想通过使用 TransactionTestCase 来“解决”这个问题，但后来没有加载固定装置，所以这种方式仍然会被破坏。
serialized_rollback = True 似乎也没有任何区别
--parallel=1 也没有区别

标签： python django postgresql fixtures

【解决方案1】：

原来，如果你有几个

super().tearDownClass()

从您的代码中丢失，这是您得到的那种症状。因此，如果您遇到这种情况，请检查您的 TestCase 是否有 tearDownClass 调用父级。

【讨论】：

【解决方案2】：

作为一种解决方法，可以标记一些测试用例，然后只运行排除标记的测试：

from django.test import tag

@tag('trouble')
class TroubleTestCase(TestCase):
...

然后运行：

python3 ./manage.py test myapp --exclude-tag=trouble

之后必须单独运行这些测试：

python3 ./manage.py test myapp --tag=trouble

【讨论】：