Add some unit testing for the new model

InvenTree/part/api.py

@@ -1281,7 +1281,6 @@ class BomItemValidate(generics.UpdateAPIView):
         return Response(serializer.data)
 
 
-
 class BomItemSubstituteList(generics.ListCreateAPIView):
     """
     API endpoint for accessing a list of BomItemSubstitute objects

InvenTree/part/models.py

@@ -2629,6 +2629,12 @@ class BomItemSubstitute(models.Model):
         # Prevent duplication of substitute parts
         unique_together = ('part', 'bom_item')
 
+    def save(self, *args, **kwargs):
+
+        self.full_clean()
+
+        super().save(*args, **kwargs)
+
     def validate_unique(self, exclude=None):
         """
         Ensure that this BomItemSubstitute is "unique":

InvenTree/part/test_bom_item.py

@@ -1,8 +1,13 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import unicode_literals
+from django.db import transaction
+
 from django.test import TestCase
 import django.core.exceptions as django_exceptions
 from decimal import Decimal
 
-from .models import Part, BomItem
+from .models import Part, BomItem, BomItemSubstitute
 
 
 class BomItemTest(TestCase):
@@ -130,3 +135,67 @@ class BomItemTest(TestCase):
             self.bob.get_bom_price_range(1, internal=True),
             (Decimal(27.5), Decimal(87.5))
         )
+
+    def test_substitutes(self):
+        """
+        Tests for BOM item substitutes
+        """
+
+        # We will make some subtitute parts for the "orphan" part
+        bom_item = BomItem.objects.get(
+            part=self.bob,
+            sub_part=self.orphan
+        )
+
+        # No substitute parts available
+        self.assertEqual(bom_item.substitutes.count(), 0)
+
+        subs = []
+
+        for ii in range(5):
+            
+            # Create a new part
+            sub_part = Part.objects.create(
+                name=f"Orphan {ii}",
+                description="A substitute part for the orphan part",
+                component=True,
+                is_template=False,
+                assembly=False,
+            )
+
+            subs.append(sub_part)
+
+            # Link it as a substitute part
+            BomItemSubstitute.objects.create(
+                bom_item=bom_item,
+                part=sub_part
+            )
+
+            # Try to link it again (this should fail as it is a duplicate substitute)
+            with self.assertRaises(django_exceptions.ValidationError):
+                with transaction.atomic():
+                    BomItemSubstitute.objects.create(
+                        bom_item=bom_item,
+                        part=sub_part
+                    )
+
+        # There should be now 5 substitute parts available
+        self.assertEqual(bom_item.substitutes.count(), 5)
+            
+        # Try to create a substitute which points to the same sub-part (should fail)
+        with self.assertRaises(django_exceptions.ValidationError):
+            BomItemSubstitute.objects.create(
+                bom_item=bom_item,
+                part=self.orphan,
+            )
+
+        # Remove one substitute part
+        bom_item.substitutes.last().delete()
+
+        self.assertEqual(bom_item.substitutes.count(), 4)
+
+        for sub in subs:
+            sub.delete()
+
+        # The substitution links should have been automatically removed
+        self.assertEqual(bom_item.substitutes.count(), 0)