Add helper to patch links when there is a conflict

This improves the documentation and testing for the existing patch_links
test helper, while adding another to simulate the response when a
version conflict occurs.

lib/gds_api/test_helpers/publishing_api_v2.rb

@@ -34,12 +34,39 @@ def stub_publishing_api_put_content(content_id, body, response_hash = {})
 
       # Stub a PATCH /v2/links/:content_id request
       #
+      # @example
+      #   stub_publishing_api_patch_links(
+      #     my_content_id,
+      #     "links" => {
+      #       "taxons" => %w(level_one_topic level_two_topic),
+      #     },
+      #     "previous_version" => "3",
+      #   )
+      #
       # @param content_id [UUID]
       # @param body  [String]
       def stub_publishing_api_patch_links(content_id, body)
         stub_publishing_api_patch(content_id, body, '/links')
       end
 
+      # Stub a PATCH /v2/links/:content_id request to return a 409 response
+      #
+      # @example
+      #   stub_publishing_api_patch_links_conflict(
+      #     my_content_id,
+      #     "links" => {
+      #       "taxons" => %w(level_one_topic level_two_topic),
+      #     },
+      #     "previous_version" => "3",
+      #   )
+      #
+      # @param content_id [UUID]
+      # @param body  [String]
+      def stub_publishing_api_patch_links_conflict(content_id, body)
+        override_response_hash = { status: 409, body: version_conflict(body[:previous_version]) }
+        stub_publishing_api_patch(content_id, body, '/links', override_response_hash)
+      end
+
       # Stub a POST /v2/content/:content_id/publish request
       #
       # @param content_id [UUID]
@@ -620,6 +647,16 @@ def resource_not_found(content_id, type)
           }
         }
       end
+
+      def version_conflict(expected_version, actual_version = expected_version + 1)
+        {
+          error: {
+            code: 409,
+            message: "A lock-version conflict occurred. The `previous_version` you've sent (#{expected_version}) is not the same as the current lock version of the edition (#{actual_version}).",
+            fields: { previous_version: ["does not match"] },
+          }
+        }
+      end
     end
   end
 end

test/test_helpers/publishing_api_v2_test.rb

@@ -234,23 +234,69 @@
     end
   end
 
-  describe "stub_any_publishing_api_publish" do
+  describe '#stub_publishing_api_patch_links' do
+    it "stubs a request to patch links" do
+      content_id = SecureRandom.uuid
+      body = {
+        links: {
+          my_linkset: %w(link_1),
+        },
+        previous_version: 4
+      }
+
+      assert_raises WebMock::NetConnectNotAllowedError do
+        publishing_api.patch_links(content_id, body)
+      end
+
+      stub_publishing_api_patch_links(content_id, body)
+      response = publishing_api.patch_links(content_id, body)
+      assert_equal(response.code, 200)
+    end
+  end
+
+  describe '#stub_publishing_api_patch_links_conflict' do
+    it "stubs a request to patch links with a 409 conflict response" do
+      content_id = SecureRandom.uuid
+      body = {
+        links: {
+          my_linkset: %w(link_1),
+        },
+        previous_version: 4
+      }
+
+      stub_publishing_api_patch_links_conflict(content_id, body)
+
+      error = assert_raises GdsApi::HTTPConflict do
+        publishing_api.patch_links(content_id, body)
+      end
+
+      assert error.message.include?({
+        error: {
+          code: 409,
+          message: "A lock-version conflict occurred. The `previous_version` you've sent (4) is not the same as the current lock version of the edition (5).",
+          fields: { previous_version: ["does not match"] },
+        }
+      }.to_json)
+    end
+  end
+
+  describe '#stub_any_publishing_api_publish' do
     it "stubs any publish request to the publishing api" do
       stub_any_publishing_api_publish
       publishing_api.publish("some-content-id", "major")
       assert_publishing_api_publish("some-content-id")
     end
   end
 
-  describe "stub_any_publishing_api_unpublish" do
+  describe '#stub_any_publishing_api_unpublish' do
     it "stubs any unpublish request to the publishing api" do
       stub_any_publishing_api_unpublish
       publishing_api.unpublish("some-content-id", type: :gone)
       assert_publishing_api_unpublish("some-content-id")
     end
   end
 
-  describe "stub_any_publishing_api_discard_draft" do
+  describe '#stub_any_publishing_api_discard_draft' do
     it "stubs any discard draft request to the publishing api" do
       stub_any_publishing_api_discard_draft
       publishing_api.discard_draft("some-content-id")