Unit testing for part variant MPTT

InvenTree/part/fixtures/part.yaml

@@ -97,4 +97,61 @@
     tree_id: 0
     level: 0
     lft: 0
-    rght: 0
+    rght: 0
+
+# A 'template' part
+- model: part.part
+  pk: 10000
+  fields:
+    name: 'Chair Template'
+    description: 'A chair'
+    is_template: True
+    category: 7
+    tree_id: 1
+    level: 0
+    lft: 0
+    rght: 0
+
+- model: part.part
+  pk: 10001
+  fields:
+    name: 'Blue Chair'
+    variant_of: 10000
+    category: 7
+    tree_id: 1
+    level: 0
+    lft: 0
+    rght: 0
+
+- model: part.part
+  pk: 10002
+  fields:
+    name: 'Red chair'
+    variant_of: 10000
+    category: 7
+    tree_id: 1
+    level: 0
+    lft: 0
+    rght: 0
+
+- model: part.part
+  pk: 10003
+  fields:
+    name: 'Green chair'
+    variant_of: 10000
+    category: 7
+    tree_id: 1
+    level: 0
+    lft: 0
+    rght: 0
+
+- model: part.part
+  pk: 10004
+  fields:
+    name: 'Green chair variant'
+    variant_of: 10003
+    category: 
+    tree_id: 1
+    level: 0
+    lft: 0
+    rght: 0

InvenTree/part/test_part.py

@@ -52,6 +52,18 @@ class PartTest(TestCase):
 
         self.C1 = Part.objects.get(name='C_22N_0805')
 
+        Part.objects.rebuild()
+
+    def test_tree(self):
+        # Test that the part variant tree is working properly
+        chair = Part.objects.get(pk=10000)
+        self.assertEqual(chair.get_children().count(), 3)
+        self.assertEqual(chair.get_descendant_count(), 4)
+
+        green = Part.objects.get(pk=10004)
+        self.assertEqual(green.get_ancestors().count(), 2)
+        self.assertEqual(green.get_root(), chair)
+
     def test_str(self):
         p = Part.objects.get(pk=100)
         self.assertEqual(str(p), "BOB | Bob | A2 - Can we build it?")