我几乎开始怀疑 Django 应用程序可以拥有的 TestCases 数量是否有一些限制，所以我需要您的帮助来弄清楚如何避免这个问题，并在我的应用程序中对所有 TestCase 进行功能测试。
我的 Django (v1.10.7( 应用程序有 4 个固定测试用例，运行良好。一旦我添加了带有夹具的第 5 个测试用例，就会运行测试 全部与
python3 ./manage.py test myapp
开始导致随机一个旧的测试用例失败，并显示：
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
新的测试用例是什么似乎并不重要，即使我用新名称复制预先存在的测试，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。
事实证明，如果你有几个
super().tearDownClass()
代码中缺少，这就是您得到的症状。因此，如果这种情况发生在您身上，请检查您的 TestCase 是否具有调用父级的 tearDownClass。
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):
...
并运行：
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