diff --git a/tests/conformance/conftest.py b/tests/conformance/conftest.py
index 91e9d0a71..e62b74e8b 100644
--- a/tests/conformance/conftest.py
+++ b/tests/conformance/conftest.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import os
+import random
 import uuid
 
 import pytest
@@ -33,16 +34,21 @@
 )
 _CONF_TEST_PUBSUB_TOPIC_NAME = "my-topic-name"
 
+
 """Create content payload in different sizes."""
 
 
 def _create_block(desired_kib):
-    line = "abc123XYZ" * 14 + "!" + "\n"
-    return 1024 * int(desired_kib / len(line)) * line
+    line = "abcdefXYZ123456789ADDINGrandom#"  # len(line) = 31
+    multiplier = int(desired_kib / (len(line) + 1))
+    lines = "".join(
+        line + str(random.randint(0, 9)) for _ in range(multiplier)
+    )  # add random single digit integers
+    return 1024 * lines
 
 
 _STRING_CONTENT = "hello world"
-_SIZE_16MB = 16384  # 16*1024 KiB
+_SIZE_9MB = 9216  # 9*1024 KiB
 
 
 ########################################################################################################################################
@@ -115,7 +121,7 @@ def hmac_key(client):
 @pytest.fixture
 def file_data(client, bucket):
     blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
-    payload = _create_block(_SIZE_16MB)
+    payload = _create_block(_SIZE_9MB)
     blob.upload_from_string(payload)
     yield blob, payload
     try:
diff --git a/tests/conformance/retry_strategy_test_data.json b/tests/conformance/retry_strategy_test_data.json
index 9c2213560..eec1b8b6c 100644
--- a/tests/conformance/retry_strategy_test_data.json
+++ b/tests/conformance/retry_strategy_test_data.json
@@ -243,8 +243,20 @@
       {
         "id": 7,
         "description": "resumable_uploads_handle_complex_retries",
-        "cases": [],
-        "methods": [],
+        "cases": [
+          {
+            "instructions": ["return-reset-connection", "return-503"]
+          },
+          {
+            "instructions": ["return-503-after-256K"]
+          },
+          {
+            "instructions": ["return-503-after-8192K"]
+          }
+        ],
+        "methods": [
+          {"name": "storage.objects.insert", "group": "storage.resumable.upload", "resources": ["BUCKET"]}
+        ],
         "preconditionProvided": true,
         "expectSuccess": true
       },
diff --git a/tests/conformance/test_conformance.py b/tests/conformance/test_conformance.py
index ff70c6e16..fa842630e 100644
--- a/tests/conformance/test_conformance.py
+++ b/tests/conformance/test_conformance.py
@@ -54,6 +54,7 @@
 
 _STRING_CONTENT = "hello world"
 _BYTE_CONTENT = b"12345678"
+_RESUMABLE_UPLOAD_CHUNK_SIZE = 2 * 1024 * 1024
 
 
 ########################################################################################################################################
@@ -461,7 +462,7 @@ def blob_upload_from_string(client, _preconditions, **resources):
     bucket = resources.get("bucket")
     _, data = resources.get("file_data")
     blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
-    blob.chunk_size = 4 * 1024 * 1024
+    blob.chunk_size = _RESUMABLE_UPLOAD_CHUNK_SIZE
     if _preconditions:
         blob.upload_from_string(data, if_generation_match=0)
     else:
@@ -471,26 +472,67 @@ def blob_upload_from_string(client, _preconditions, **resources):
 
 def blob_upload_from_file(client, _preconditions, **resources):
     bucket = resources.get("bucket")
-    blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
+    file, data = resources.get("file_data")
+    file_blob = client.bucket(bucket.name).blob(file.name)
+    upload_blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
+    upload_blob.chunk_size = _RESUMABLE_UPLOAD_CHUNK_SIZE
+
     with tempfile.NamedTemporaryFile() as temp_f:
+        # Create a named temporary file with payload.
+        with open(temp_f.name, "wb") as file_obj:
+            client.download_blob_to_file(file_blob, file_obj)
+        # Upload the temporary file and assert data integrity.
         if _preconditions:
-            blob.upload_from_file(temp_f, if_generation_match=0)
+            upload_blob.upload_from_file(temp_f, if_generation_match=0)
         else:
-            blob.upload_from_file(temp_f)
+            upload_blob.upload_from_file(temp_f)
+
+    upload_blob.reload()
+    assert upload_blob.size == len(data)
 
 
 def blob_upload_from_filename(client, _preconditions, **resources):
     bucket = resources.get("bucket")
     blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
+    blob.chunk_size = _RESUMABLE_UPLOAD_CHUNK_SIZE
+
+    bucket = resources.get("bucket")
+    file, data = resources.get("file_data")
+    file_blob = client.bucket(bucket.name).blob(file.name)
+    upload_blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
+    upload_blob.chunk_size = _RESUMABLE_UPLOAD_CHUNK_SIZE
 
     with tempfile.NamedTemporaryFile() as temp_f:
+        # Create a named temporary file with payload.
+        with open(temp_f.name, "wb") as file_obj:
+            client.download_blob_to_file(file_blob, file_obj)
+        # Upload the temporary file and assert data integrity.
         if _preconditions:
-            blob.upload_from_filename(temp_f.name, if_generation_match=0)
+            upload_blob.upload_from_filename(temp_f.name, if_generation_match=0)
         else:
-            blob.upload_from_filename(temp_f.name)
+            upload_blob.upload_from_filename(temp_f.name)
+
+    upload_blob.reload()
+    assert upload_blob.size == len(data)
 
 
 def blobwriter_write(client, _preconditions, **resources):
+    bucket = resources.get("bucket")
+    _, data = resources.get("file_data")
+    blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
+    if _preconditions:
+        with blob.open(
+            "w", chunk_size=_RESUMABLE_UPLOAD_CHUNK_SIZE, if_generation_match=0
+        ) as writer:
+            writer.write(data)
+    else:
+        with blob.open("w", chunk_size=_RESUMABLE_UPLOAD_CHUNK_SIZE) as writer:
+            writer.write(data)
+    blob.reload()
+    assert blob.size == len(data)
+
+
+def blobwriter_write_multipart(client, _preconditions, **resources):
     chunk_size = 256 * 1024
     bucket = resources.get("bucket")
     blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
@@ -502,6 +544,15 @@ def blobwriter_write(client, _preconditions, **resources):
             writer.write(_BYTE_CONTENT)
 
 
+def blob_upload_from_string_multipart(client, _preconditions, **resources):
+    bucket = resources.get("bucket")
+    blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
+    if _preconditions:
+        blob.upload_from_string(_STRING_CONTENT, if_generation_match=0)
+    else:
+        blob.upload_from_string(_STRING_CONTENT)
+
+
 def blob_create_resumable_upload_session(client, _preconditions, **resources):
     bucket = resources.get("bucket")
     blob = client.bucket(bucket.name).blob(uuid.uuid4().hex)
@@ -745,11 +796,15 @@ def object_acl_clear(client, _preconditions, **resources):
         bucket_rename_blob,
     ],
     "storage.objects.insert": [
+        blob_upload_from_string_multipart,
+        blobwriter_write_multipart,
+        blob_create_resumable_upload_session,
+    ],
+    "storage.resumable.upload": [
         blob_upload_from_string,
         blob_upload_from_file,
         blob_upload_from_filename,
         blobwriter_write,
-        blob_create_resumable_upload_session,
     ],
     "storage.objects.patch": [
         blob_patch,