diff --git a/services/commtest/tests/backup_test.rs b/services/commtest/tests/backup_test.rs
--- a/services/commtest/tests/backup_test.rs
+++ b/services/commtest/tests/backup_test.rs
@@ -22,6 +22,8 @@
   let mut client =
     BackupServiceClient::connect("http://localhost:50052").await?;
 
+  let attachments_fill_size = 500;
+
   let mut backup_data = BackupData {
     user_id: "user0000".to_string(),
     device_id: "device0000".to_string(),
@@ -40,7 +42,7 @@
       // In this case its data should be moved to the S3
       Item::new(
         String::new(),
-        vec![tools::get_dynamo_db_item_size_limit() - ByteSize::b(100).as_u64() as usize],
+        vec![tools::get_dynamo_db_item_size_limit() - ByteSize::b(attachments_fill_size/2).as_u64() as usize],
         vec!["holder0".to_string(), "holder1".to_string()],
       ),
       // just a small item
@@ -130,7 +132,7 @@
   // from the db to the s3
   let mut attachments_size = 0;
   let mut i = backup_data.log_items[0].attachments_holders.len();
-  let mut new_attachments: Vec<String> = vec![];
+  let mut new_attachments: Vec<String> = Vec::new();
   while attachments_size < 500 {
     let att = format!("holder{}", i);
     attachments_size += att.len();
@@ -150,8 +152,42 @@
   for i in 0..backup_data.log_items.len() {
     let expected: usize = backup_data.log_items[i].attachments_holders.len();
     let from_result: usize = result.log_items[i].attachments_holders.len();
-    assert!(
-      from_result == expected,
+    assert_eq!(
+      from_result, expected,
+      "after attachment add: log {}: number of attachments holders do not match,
+      expected {}, got {}",
+      i,
+      expected,
+      from_result
+    );
+  }
+
+  // push so many attachments that the log item's data will have to be moved
+  // from the db to the s3
+  let mut attachments_size = 0;
+  let mut i = backup_data.log_items[0].attachments_holders.len();
+  let mut new_attachments: Vec<String> = Vec::new();
+  while attachments_size < attachments_fill_size {
+    let att = format!("holder{}", i);
+    attachments_size += att.len();
+    new_attachments.push(att);
+    i += 1;
+  }
+
+  let mut old_attachments =
+    backup_data.log_items[0].attachments_holders.clone();
+  backup_data.log_items[0].attachments_holders = new_attachments;
+  add_attachments::run(&mut client, &backup_data, Some(0)).await?;
+  backup_data.log_items[0]
+    .attachments_holders
+    .append(&mut old_attachments);
+  let result = pull_backup::run(&mut client, &backup_data).await?;
+  // check logs attachments
+  for i in 0..backup_data.log_items.len() {
+    let expected: usize = backup_data.log_items[i].attachments_holders.len();
+    let from_result: usize = result.log_items[i].attachments_holders.len();
+    assert_eq!(
+      from_result, expected,
       "after attachment add: log {}: number of attachments holders do not match,
       expected {}, got {}",
       i,