python - 运行单个测试文件时 Django 测试设置失败

Question

直接症状：

$ pytest …/apps/users/test/test_graph_permissions_command.py
============================= test session starts ==============================
platform linux -- Python 3.6.8, pytest-4.6.2, py-1.8.0, pluggy-0.12.0
Django settings: dms.settings (from ini file)
rootdir: /src/app, inifile: pytest.ini
plugins: forked-1.0.2, celery-4.3.0, django-3.5.0, cov-2.7.1, xdist-1.28.0
collected 1 item                                                               

…/apps/users/test/test_graph_permissions_command.py E

==================================== ERRORS ====================================
_ ERROR at setup of TestGraphPermissionsCommand.test_should_resolve_a_permission_hierarchy _
.venv/lib/python3.6/site-packages/pytest_django/plugin.py:519: in _django_setup_unittest
    request.getfixturevalue("django_db_setup")
.venv/lib/python3.6/site-packages/pytest_django/fixtures.py:108: in django_db_setup
    **setup_databases_args
.venv/lib/python3.6/site-packages/django/test/utils.py:174: in setup_databases
    serialize=connection.settings_dict.get('TEST', {}).get('SERIALIZE', True),
.venv/lib/python3.6/site-packages/django/db/backends/base/creation.py:80: in create_test_db
    self.connection._test_serialized_contents = self.serialize_db_to_string()
.venv/lib/python3.6/site-packages/django/db/backends/base/creation.py:123: in serialize_db_to_string
    serializers.serialize("json", get_objects(), indent=None, stream=out)
.venv/lib/python3.6/site-packages/django/core/serializers/__init__.py:128: in serialize
    s.serialize(queryset, **options)
.venv/lib/python3.6/site-packages/django/core/serializers/base.py:90: in serialize
    for count, obj in enumerate(queryset, start=1):
.venv/lib/python3.6/site-packages/django/db/backends/base/creation.py:120: in get_objects
    yield from queryset.iterator()
.venv/lib/python3.6/site-packages/django/db/models/query.py:341: in _iterator
    yield from self._iterable_class(self, chunked_fetch=use_chunked_fetch, chunk_size=chunk_size)
.venv/lib/python3.6/site-packages/polymorphic/query.py:56: in _polymorphic_iterator
    o = next(base_iter)
.venv/lib/python3.6/site-packages/django/db/models/query.py:55: in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
.venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py:1087: in execute_sql
    sql, params = self.as_sql()
.venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py:474: in as_sql
    extra_select, order_by, group_by = self.pre_sql_setup()
.venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py:54: in pre_sql_setup
    self.setup_query()
.venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py:45: in setup_query
    self.select, self.klass_info, self.annotation_col_map = self.get_select()
.venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py:219: in get_select
    cols = self.get_default_columns()
.venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py:666: in get_default_columns
    column = field.get_col(alias)
.venv/lib/python3.6/site-packages/django/db/models/fields/related.py:981: in get_col
    output_field = self.target_field
.venv/lib/python3.6/site-packages/django/db/models/fields/related.py:878: in target_field
    return self.foreign_related_fields[0]
.venv/lib/python3.6/site-packages/django/db/models/fields/related.py:632: in foreign_related_fields
    return tuple(rhs_field for lhs_field, rhs_field in self.related_fields if rhs_field)
.venv/lib/python3.6/site-packages/django/db/models/fields/related.py:619: in related_fields
    self._related_fields = self.resolve_related_fields()
.venv/lib/python3.6/site-packages/django/db/models/fields/related.py:604: in resolve_related_fields
    raise ValueError('Related model %r cannot be resolved' % self.remote_field.model)
E   ValueError: Related model 'appname.ModelName' cannot be resolved
=========================== 1 error in 5.54 seconds ============================

测试文件：

$ cat …/apps/users/test/test_graph_permissions_command.py
from django.test import TestCase


class TestGraphPermissionsCommand(TestCase):
    def test_should_resolve_a_permission_hierarchy(self) -> None:
        pass

情况：

1. 用另一个文件测试 test_graph_permissions_command.py可以正常工作 - 任何其他文件似乎都可以工作，无论 test_graph_permissions_command.py 是第一个还是最后一个都可以。
2. TestCase从而不是导入unittest工作，但我需要django.test.TestCase在实际测试中的一些东西。
3. 测试任何其他单个文件也可以。
4. 我重建了每晚运行的虚拟机，一位同事能够重现这个问题，所以这不是我的设置所独有的。
5. ./manage.py makemigrations报告“未检测到更改”。
6. 许多其他测试类从同一个类继承TestCase而没有问题。
7. 错误消息中的应用程序和模型经过了很好的测试。同样适用于两个模型，每个模型都有ForeignKeyto "appname.ModelName"。代码覆盖率为 98%。

这里发生了什么？看起来这可能是由于测试数据库构建器未能以正确的顺序执行操作造成的。

标签： pythondjangopython-3.xdjango-rest-framework