Fixed #7825 - modeltests/delete tests failing after NFA merge, and improved...

__test__ = {'API_TESTS': """

# First, some tests for the datastructure we use

### Tests for models A,B,C,D ###

## First, test the CollectedObjects data structure directly

>>> from django.db.models.query import CollectedObjects

CyclicDependency: There is a cyclic dependency of items to be processed.

## Second, test the usage of CollectedObjects by Model.delete()

# Due to the way that transactions work in the test harness,

# doing m.delete() here can work but fail in a real situation,

# then try again with a known 'tricky' order.  Slightly naughty

# access to internals here :-)

# If implementation changes, then the tests may need to be simplified:

#  - remove the lines that set the .keyOrder and clear the related

#    object caches

#  - remove the second set of tests (with a2, b2 etc)

>>> from django.db.models.loading import cache

>>> def clear_rel_obj_caches(models):

...     for m in models:

...         if hasattr(m._meta, '_related_objects_cache'): 

...             del m._meta._related_objects_cache

# Nice order

>>> cache.app_models['delete'].keyOrder = ['a', 'b', 'c', 'd']

>>> del A._meta._related_objects_cache

>>> del B._meta._related_objects_cache

>>> del C._meta._related_objects_cache

>>> del D._meta._related_objects_cache

>>> clear_rel_obj_caches([A, B, C, D])

>>> a1 = A()

>>> a1.save()

# Same again with a known bad order

>>> cache.app_models['delete'].keyOrder = ['d', 'c', 'b', 'a']

>>> del A._meta._related_objects_cache

>>> del B._meta._related_objects_cache

>>> del C._meta._related_objects_cache

>>> del D._meta._related_objects_cache

>>> clear_rel_obj_caches([A, B, C, D])

>>> a2 = A()

>>> a2.save()

[<class 'modeltests.delete.models.D'>, <class 'modeltests.delete.models.C'>, <class 'modeltests.delete.models.B'>, <class 'modeltests.delete.models.A'>]

>>> a2.delete()

# Tests for nullable related fields

### Tests for models E,F - nullable related fields ###

## First, test the CollectedObjects data structure directly

>>> g = CollectedObjects()

>>> g.add("key1", 1, "item1", None)

>>> g.ordered_keys()

['key1', 'key2']

## Second, test the usage of CollectedObjects by Model.delete()

>>> e1 = E()

>>> e1.save()

>>> f1 = F(e=e1)