diff --git a/test/net/imap/fixtures/response_parser/uidplus_extension.yml b/test/net/imap/fixtures/response_parser/uidplus_extension.yml
index c2f084c4..bbb1c0bc 100644
--- a/test/net/imap/fixtures/response_parser/uidplus_extension.yml
+++ b/test/net/imap/fixtures/response_parser/uidplus_extension.yml
@@ -10,11 +10,10 @@
       data: !ruby/struct:Net::IMAP::ResponseText
         code: !ruby/struct:Net::IMAP::ResponseCode
           name: APPENDUID
-          data: !ruby/struct:Net::IMAP::UIDPlusData
+          data: !ruby/object:Net::IMAP::AppendUIDData
             uidvalidity: 38505
-            source_uids:
-            assigned_uids:
-            - 3955
+            assigned_uids: !ruby/object:Net::IMAP::SequenceSet
+              string: '3955'
         text: APPEND completed
       raw_data: "A003 OK [APPENDUID 38505 3955] APPEND completed\r\n"
 
@@ -27,16 +26,12 @@
       data: !ruby/struct:Net::IMAP::ResponseText
         code: !ruby/struct:Net::IMAP::ResponseCode
           name: COPYUID
-          data: !ruby/struct:Net::IMAP::UIDPlusData
+          data: !ruby/object:Net::IMAP::CopyUIDData
             uidvalidity: 38505
-            source_uids:
-            - 304
-            - 319
-            - 320
-            assigned_uids:
-            - 3956
-            - 3957
-            - 3958
+            source_uids: !ruby/object:Net::IMAP::SequenceSet
+              string: 304,319:320
+            assigned_uids: !ruby/object:Net::IMAP::SequenceSet
+              string: 3956:3958
         text: Done
       raw_data: "A004 OK [COPYUID 38505 304,319:320 3956:3958] Done\r\n"
 
@@ -48,14 +43,10 @@
       data: !ruby/struct:Net::IMAP::ResponseText
         code: !ruby/struct:Net::IMAP::ResponseCode
           name: APPENDUID
-          data: !ruby/struct:Net::IMAP::UIDPlusData
+          data: !ruby/object:Net::IMAP::AppendUIDData
             uidvalidity: 2
-            source_uids:
-            assigned_uids:
-            - 4
-            - 6
-            - 7
-            - 9
+            assigned_uids: !ruby/object:Net::IMAP::SequenceSet
+              string: 4,6:7,9
         text: APPEND completed
       raw_data: "A003 OK [APPENDUID 2 4,6:7,9] APPEND completed\r\n"
 
@@ -71,25 +62,11 @@
       data: !ruby/struct:Net::IMAP::ResponseText
         code: !ruby/struct:Net::IMAP::ResponseCode
           name: COPYUID
-          data: !ruby/struct:Net::IMAP::UIDPlusData
+          data: !ruby/object:Net::IMAP::CopyUIDData
             uidvalidity: 9999
-            source_uids:
-            - 19
-            - 20
-            - 495
-            - 496
-            - 497
-            - 498
-            - 499
-            - 500
-            assigned_uids:
-            - 92
-            - 93
-            - 94
-            - 95
-            - 96
-            - 97
-            - 100
-            - 101
+            source_uids: !ruby/object:Net::IMAP::SequenceSet
+              string: 20:19,500:495
+            assigned_uids: !ruby/object:Net::IMAP::SequenceSet
+              string: 92:97,101:100
         text: Done
       raw_data: "A004 OK [copyUID 9999 20:19,500:495 92:97,101:100] Done\r\n"
diff --git a/test/net/imap/test_imap_uidplus.rb b/test/net/imap/test_imap_uidplus.rb
index d19af5f7..426f988c 100644
--- a/test/net/imap/test_imap_uidplus.rb
+++ b/test/net/imap/test_imap_uidplus.rb
@@ -8,6 +8,11 @@
 class IMAPUIDPlusTest < Net::IMAP::TestCase
   include Net::IMAP::FakeServer::TestHelper
 
+  def setup
+    super
+    Net::IMAP.config.parser_use_deprecated_uidplus_data = false
+  end
+
   def test_uidplus_appenduid
     with_fake_server(select: "INBOX",
                      extensions: %i[UIDPLUS]) do |server, imap|
@@ -21,7 +26,10 @@ def test_uidplus_appenduid
 
         hello world
       EOF
-      assert_equal([38505, nil, [3955]], resp.data.code.data.to_a)
+      code = resp.data.code
+      assert_equal("APPENDUID", code.name)
+      assert_equal(38505,       code.data.uidvalidity)
+      assert_equal([3955],      code.data.assigned_uids.numbers)
       assert_equal "APPEND", server.commands.pop.name
     end
   end
@@ -33,12 +41,13 @@ def test_uidplus_copyuid_multiple
         cmd.done_ok code: "COPYUID 38505 3955,3960:3962 3963:3966"
       end
       resp = imap.uid_copy([3955,3960..3962], 'trash')
+      code = resp.data.code
       cmd  = server.commands.pop
       assert_equal(["UID COPY", "3955,3960:3962 trash"], [cmd.name, cmd.args])
-      assert_equal(
-        [38505, [3955, 3960, 3961, 3962], [3963, 3964, 3965, 3966]],
-        resp.data.code.data.to_a
-      )
+      assert_equal("COPYUID", code.name)
+      assert_equal(38505, code.data.uidvalidity)
+      assert_equal([3955, 3960, 3961, 3962], code.data.source_uids.numbers)
+      assert_equal([3963, 3964, 3965, 3966], code.data.assigned_uids.numbers)
     end
   end
 
@@ -49,9 +58,13 @@ def test_uidplus_copyuid_single
         cmd.done_ok code: "COPYUID 38505 3955 3967"
       end
       resp = imap.uid_copy(3955, 'trash')
+      code = resp.data.code
       cmd  = server.commands.pop
       assert_equal(["UID COPY", "3955 trash"], [cmd.name, cmd.args])
-      assert_equal([38505, [3955], [3967]], resp.data.code.data.to_a)
+      assert_equal("COPYUID", code.name)
+      assert_equal(38505, code.data.uidvalidity)
+      assert_equal([3955], code.data.source_uids.numbers)
+      assert_equal([3967], code.data.assigned_uids.numbers)
     end
   end
 
diff --git a/test/net/imap/test_response_parser.rb b/test/net/imap/test_response_parser.rb
index f6a4b756..ee54a24d 100644
--- a/test/net/imap/test_response_parser.rb
+++ b/test/net/imap/test_response_parser.rb
@@ -10,6 +10,11 @@ class ResponseParserTest < Net::IMAP::TestCase
   include NetIMAPTestHelpers
   extend  NetIMAPTestHelpers::TestFixtureGenerators
 
+  def setup
+    super
+    Net::IMAP.config.parser_use_deprecated_uidplus_data = false
+  end
+
   ############################################################################
   # Tests that do no more than parse an example response and assert the result
   # data has the correct values have been moved to yml test fixtures.