Add tests for default location traversal

InvenTree/part/fixtures/category.yaml

@@ -6,7 +6,7 @@
     name: Electronics
     description: Electronic components
     parent: null
-    default_location: null
+    default_location: 1  # Home
 - model: part.partcategory
   pk: 2
   fields:
@@ -54,3 +54,4 @@
     name: Fasteners
     description: Screws, bolts, etc
     parent: 7
+    default_location: 5

InvenTree/part/fixtures/part.yaml

@@ -23,10 +23,17 @@
     name: 'R_4K7_0603'
     description: '4.7kOhm resistor in 0603 package'
     category: 2
+    default_location: 2  # Home/Bathroom
 
 # Create some capacitors
 - model: part.part
   fields:
     name: 'C_22N_0805'
     description: '22nF capacitor in 0805 package'
-    category: 3
+    category: 3
+
+- model: part.part
+  fields:
+    name: 'Widget'
+    description: 'A watchamacallit'
+    category: 7