Add missing tests for shipment state after cancel

When cancelling all items in a completed order, if the shipment is not
already shipped, it should be marked as cancelled. However, if the
shipment has already shipped, we should maintain its state because we
treat that state as immutable.

Author: adammathys

core/spec/models/spree/order_cancellations_spec.rb

@@ -109,6 +109,32 @@
       it "adjusts the order" do
         expect { subject }.to change { order.reload.total }.by(-40.0)
       end
+
+      context "when cancelling all items in a completed order" do
+        let!(:order) { create(:completed_order_with_totals, line_items_attributes: [{ quantity: }]) }
+
+        subject { described_class.new(order).short_ship(order.inventory_units) }
+
+        it "updates all of the inventory units" do
+          expect { subject }.to change { order.inventory_units.canceled.count }.to(quantity)
+        end
+
+        it "updates the shipment state" do
+          expect { subject }.to change { order.shipments.first.reload.state }.to("canceled")
+        end
+
+        context "when the shipment is already shipped" do
+          let!(:order) { create(:shipped_order, line_items_attributes: [{ quantity: }]) }
+
+          it "updates all of the inventory units" do
+            expect { subject }.to change { order.inventory_units.canceled.count }.to(quantity)
+          end
+
+          it "does not update the shipment state" do
+            expect { subject }.not_to change { order.shipments.first.reload.state }.from("shipped")
+          end
+        end
+      end
     end
 
     it "sends a cancellation email" do