Test order of linked-to editions in dataloader

We removed an implicit assertion on this from other tests which had
broken following the introduction of a UNION, so we're testing the
impact of the ORDER more explicitly here

Co-authored-by: Mike Patrick <mike.patrick2@digital.cabinet-office.gov.uk>

spec/graphql/sources/linked_to_editions_source_spec.rb

@@ -105,4 +105,32 @@
       expect(request.load).to match_array([target_edition_3, target_edition_4])
     end
   end
+
+  it "returns editions in order of their associated link's `position`" do
+    target_edition_0 = create(:edition)
+    target_edition_1 = create(:edition)
+    target_edition_2 = create(:edition)
+    target_edition_3 = create(:edition)
+
+    source_edition = create(:edition, content_store: "draft")
+    create(:link, edition: source_edition, target_content_id: target_edition_1.content_id, position: 1, link_type: "test_link")
+    create(:link, edition: source_edition, target_content_id: target_edition_3.content_id, position: 3, link_type: "test_link")
+
+    link_set = create(:link_set, content_id: source_edition.content_id)
+    create(:link, link_set:, target_content_id: target_edition_0.content_id, position: 0, link_type: "test_link")
+    create(:link, link_set:, target_content_id: target_edition_2.content_id, position: 2, link_type: "test_link")
+
+    GraphQL::Dataloader.with_dataloading do |dataloader|
+      request = dataloader.with(
+        described_class,
+        content_store: source_edition.content_store,
+      ).request([
+        source_edition,
+        "test_link",
+        %i[id base_path title document_id],
+      ])
+
+      expect(request.load).to eq([target_edition_0, target_edition_1, target_edition_2, target_edition_3])
+    end
+  end
 end