Refs #26678 -- Added tests for using the field the relation points to with RelatedManager.add()/remove()/set().

tests/many_to_many/models.py

@@ -38,6 +38,7 @@ class Article(models.Model):
     # correctly created. Refs #20207
     publications = models.ManyToManyField(Publication, name='publications')
     tags = models.ManyToManyField(Tag, related_name='tags')
+    authors = models.ManyToManyField('User', through='UserArticle')
 
     objects = NoDeletedArticleManager()
 
@@ -48,6 +49,18 @@ class Article(models.Model):
         return self.headline
 
 
+class User(models.Model):
+    username = models.CharField(max_length=20, unique=True)
+
+    def __str__(self):
+        return self.username
+
+
+class UserArticle(models.Model):
+    user = models.ForeignKey(User, models.CASCADE, to_field='username')
+    article = models.ForeignKey(Article, models.CASCADE)
+
+
 # Models to test correct related_name inheritance
 class AbstractArticle(models.Model):
     class Meta:

tests/many_to_many/tests.py

@@ -3,7 +3,9 @@ from unittest import mock
 from django.db import transaction
 from django.test import TestCase, skipUnlessDBFeature
 
-from .models import Article, InheritedArticleA, InheritedArticleB, Publication
+from .models import (
+    Article, InheritedArticleA, InheritedArticleB, Publication, User,
+)
 
 
 class ManyToManyTests(TestCase):
@@ -76,6 +78,32 @@ class ManyToManyTests(TestCase):
             ]
         )
 
+    def test_add_remove_set_by_pk(self):
+        a5 = Article.objects.create(headline='Django lets you create Web apps easily')
+        a5.publications.add(self.p1.pk)
+        self.assertQuerysetEqual(
+            a5.publications.all(),
+            ['<Publication: The Python Journal>'],
+        )
+        a5.publications.set([self.p2.pk])
+        self.assertQuerysetEqual(
+            a5.publications.all(),
+            ['<Publication: Science News>'],
+        )
+        a5.publications.remove(self.p2.pk)
+        self.assertQuerysetEqual(a5.publications.all(), [])
+
+    def test_add_remove_set_by_to_field(self):
+        user_1 = User.objects.create(username='Jean')
+        user_2 = User.objects.create(username='Joe')
+        a5 = Article.objects.create(headline='Django lets you create Web apps easily')
+        a5.authors.add(user_1.username)
+        self.assertQuerysetEqual(a5.authors.all(), ['<User: Jean>'])
+        a5.authors.set([user_2.username])
+        self.assertQuerysetEqual(a5.authors.all(), ['<User: Joe>'])
+        a5.authors.remove(user_2.username)
+        self.assertQuerysetEqual(a5.authors.all(), [])
+
     def test_reverse_add(self):
         # Adding via the 'other' end of an m2m
         a5 = Article(headline='NASA finds intelligent life on Mars')