Failing test for custom foreign key

simple_history/tests/models.py

@@ -1,9 +1,9 @@
 from django.db import models
+from django.conf import settings
 from django.contrib.auth.models import User
 from simple_history.models import HistoricalRecords
 from simple_history import register
 
-
 class Poll(models.Model):
     question = models.CharField(max_length=200)
     pub_date = models.DateTimeField('date published')
@@ -45,7 +45,6 @@ class FileModel(models.Model):
     file = models.FileField(upload_to='files')
     history = HistoricalRecords()
 
-
 class Document(models.Model):
     changed_by = models.ForeignKey(User, null=True)
     history = HistoricalRecords()
@@ -54,6 +53,18 @@ class Document(models.Model):
     def _history_user(self):
         return self.changed_by
 
+class Book(models.Model):
+    isbn = models.CharField(max_length=15, primary_key=True)
+    changed_by = models.ForeignKey(User, null=True)
+    history = HistoricalRecords()
+
+    @property
+    def _history_user(self):
+        return self.changed_by
+
+class Library(models.Model):
+    book = models.ForeignKey(Book, null=True)
+    history = HistoricalRecords()
 
 register(User, app='simple_history.tests', manager_name='histories')
 

simple_history/tests/tests.py

@@ -6,7 +6,7 @@
 from django.core.urlresolvers import reverse
 from django.contrib.auth.models import User
 
-from .models import Poll, Choice, Restaurant, Person, FileModel, Document
+from .models import Poll, Choice, Restaurant, Person, FileModel, Document, Book, Library
 from .models import ExternalModel1, ExternalModel3
 from simple_history import register
 from simple_history.tests.external.models import ExternalModel2, ExternalModel4
@@ -169,6 +169,18 @@ def test_specify_history_user(self):
         self.assertEqual([d.history_user for d in document.history.all()],
                          [None, user2, user1])
 
+    def test_non_default_primary_key_save(self):
+        book1 = Book.objects.create(isbn='1-84356-028-1')
+        book2 = Book.objects.create(isbn='1-84356-028-2')
+        library = Library.objects.create(book=book1)
+        library.book = book2
+        library.save()
+        library.book = None
+        library.save()
+        self.assertEqual([l.book for l in library.history.all()],
+                         [None, book2, book1])
+
+
     def test_raw_save(self):
         document = Document()
         document.save_base(raw=True)
@@ -180,7 +192,6 @@ def test_raw_save(self):
             'history_type': "~",
         })
 
-
 class RegisterTest(TestCase):
     def test_register_no_args(self):
         self.assertEqual(len(Choice.history.all()), 0)