diff --git a/InvenTree/part/test_category.py b/InvenTree/part/test_category.py
index 53030d402a..6eb76fa845 100644
--- a/InvenTree/part/test_category.py
+++ b/InvenTree/part/test_category.py
@@ -172,3 +172,122 @@ class CategoryTest(TestCase):
         # And one part should have no default location at all
         w = Part.objects.get(name='Widget')
         self.assertIsNone(w.get_default_location())
+
+    def test_category_tree(self):
+        """
+        Unit tests for the part category tree structure (MPTT)
+        Ensure that the MPTT structure is rebuilt correctly,
+        and the correct ancestor tree is observed.
+        """
+
+        # Clear out any existing parts
+        Part.objects.all().delete()
+
+        # First, create a structured tree of part categories
+        A = PartCategory.objects.create(
+            name='A',
+            description='Top level category',
+        )
+
+        B1 = PartCategory.objects.create(name='B1', parent=A)
+        B2 = PartCategory.objects.create(name='B2', parent=A)
+        B3 = PartCategory.objects.create(name='B3', parent=A)
+
+        C11 = PartCategory.objects.create(name='C11', parent=B1)
+        C12 = PartCategory.objects.create(name='C12', parent=B1)
+        C13 = PartCategory.objects.create(name='C13', parent=B1)
+
+        C21 = PartCategory.objects.create(name='C21', parent=B2)
+        C22 = PartCategory.objects.create(name='C22', parent=B2)
+        C23 = PartCategory.objects.create(name='C23', parent=B2)
+
+        C31 = PartCategory.objects.create(name='C31', parent=B3)
+        C32 = PartCategory.objects.create(name='C32', parent=B3)
+        C33 = PartCategory.objects.create(name='C33', parent=B3)
+
+        # Check that the tree_id value is correct
+        for cat in [B1, B2, B3, C11, C22, C33]:
+            self.assertEqual(cat.tree_id, A.tree_id)
+            self.assertEqual(cat.level, cat.parent.level + 1)
+            self.assertEqual(cat.get_ancestors().count(), cat.level)
+
+        # Spot check for C31
+        ancestors = C31.get_ancestors(include_self=True)
+
+        self.assertEqual(ancestors.count(), 3)
+        self.assertEqual(ancestors[0], A)
+        self.assertEqual(ancestors[1], B3)
+        self.assertEqual(ancestors[2], C31)
+
+        # At this point, we are confident that the tree is correctly structured
+
+        # Add some parts to category B3
+
+        for i in range(10):
+            Part.objects.create(
+                name=f'Part {i}',
+                description='A test part',
+                category=B3,
+            )
+
+        self.assertEqual(Part.objects.filter(category=B3).count(), 10)
+        self.assertEqual(Part.objects.filter(category=A).count(), 0)
+
+        # Delete category B3
+        B3.delete()
+
+        # Child parts have been moved to category A
+        self.assertEqual(Part.objects.filter(category=A).count(), 10)
+
+        for cat in [C31, C32, C33]:
+            # These categories should now be directly under A
+            cat.refresh_from_db()
+
+            self.assertEqual(cat.parent, A)
+            self.assertEqual(cat.level, 1)
+            self.assertEqual(cat.get_ancestors().count(), 1)
+            self.assertEqual(cat.get_ancestors()[0], A)
+
+        # Now, delete category A
+        A.delete()
+
+        # Parts have now been moved to the top-level category
+        self.assertEqual(Part.objects.filter(category=None).count(), 10)
+
+        for loc in [B1, B2, C31, C32, C33]:
+            # These should now all be "top level" categories
+            loc.refresh_from_db()
+
+            self.assertEqual(loc.level, 0)
+            self.assertEqual(loc.parent, None)
+
+        # Check descendants for B1
+        descendants = B1.get_descendants()
+        self.assertEqual(descendants.count(), 3)
+
+        for loc in [C11, C12, C13]:
+            self.assertTrue(loc in descendants)
+
+        # Check category C1x, should be B1 -> C1x
+        for loc in [C11, C12, C13]:
+            loc.refresh_from_db()
+
+            self.assertEqual(loc.level, 1)
+            self.assertEqual(loc.parent, B1)
+            ancestors = loc.get_ancestors(include_self=True)
+
+            self.assertEqual(ancestors.count(), 2)
+            self.assertEqual(ancestors[0], B1)
+            self.assertEqual(ancestors[1], loc)
+
+        # Check category C2x, should be B2 -> C2x
+        for loc in [C21, C22, C23]:
+            loc.refresh_from_db()
+
+            self.assertEqual(loc.level, 1)
+            self.assertEqual(loc.parent, B2)
+            ancestors = loc.get_ancestors(include_self=True)
+
+            self.assertEqual(ancestors.count(), 2)
+            self.assertEqual(ancestors[0], B2)
+            self.assertEqual(ancestors[1], loc)
diff --git a/InvenTree/stock/tests.py b/InvenTree/stock/tests.py
index 20dc562f54..50f77a593b 100644
--- a/InvenTree/stock/tests.py
+++ b/InvenTree/stock/tests.py
@@ -688,7 +688,6 @@ class StockTest(TestCase):
         self.assertEqual(C22.parent, B2)
 
         ancestors = C21.get_ancestors()
-        print("C21 ancestors:", ancestors)
 
         self.assertEqual(C21.get_ancestors().count(), 1)
         self.assertEqual(C22.get_ancestors().count(), 1)