diff --git a/pyinfra/rest.py b/pyinfra/rest.py
index 3591fd3..0766ced 100644
--- a/pyinfra/rest.py
+++ b/pyinfra/rest.py
@@ -2,7 +2,7 @@ from operator import itemgetter
 
 from funcy import compose
 
-from pyinfra.utils.func import star
+from pyinfra.utils.func import star, lift, lstarlift
 from test.utils.server import bytes_to_string, string_to_bytes
 
 
@@ -21,5 +21,9 @@ def bundle(data: bytes, metadata: dict):
     return package
 
 
-def wrap_operation(operation):
+def unpack_op_pack(operation):
     return compose(star(pack), star(operation), unpack)
+
+
+def unpack_batchop_pack(operation):
+    return compose(lstarlift(pack), operation, lift(unpack))
diff --git a/pyinfra/utils/func.py b/pyinfra/utils/func.py
index 8b7ed08..fed8161 100644
--- a/pyinfra/utils/func.py
+++ b/pyinfra/utils/func.py
@@ -15,6 +15,10 @@ def starlift(fn):
     return curry(starmap)(fn)
 
 
+def lstarlift(fn):
+    return compose(list, starlift(fn))
+
+
 def parallel(*fs):
     return lambda *args: (f(a) for f, a in zip(fs, args))
 
diff --git a/test/fixtures/server.py b/test/fixtures/server.py
index d1d0a96..e0a94a7 100644
--- a/test/fixtures/server.py
+++ b/test/fixtures/server.py
@@ -7,12 +7,12 @@ import fitz
 import pytest
 import requests
 from PIL import Image
-from funcy import retry
+from funcy import retry, compose
 from waitress import serve
 
-from pyinfra.rest import wrap_operation
+from pyinfra.rest import unpack_op_pack, unpack_batchop_pack
 from pyinfra.utils.buffer import bufferize
-from pyinfra.utils.func import llift
+from pyinfra.utils.func import llift, starlift
 from test.server import set_up_processing_server
 from test.utils.image import image_to_bytes
 
@@ -45,10 +45,12 @@ def server(processor_fn):
 
 @pytest.fixture
 def processor_fn(operation, buffer_size, batched):
-    operation = wrap_operation(operation)
 
-    if not batched:
-        operation = llift(operation)
+    if batched:
+        operation = starlift(operation)
+
+    wrapper = unpack_batchop_pack if batched else compose(llift, unpack_op_pack)
+    operation = wrapper(operation)
 
     return bufferize(operation, buffer_size=buffer_size, persist_fn=attrgetter("json"))
 
@@ -66,24 +68,18 @@ def operation(item_type, batched):
         for page in fitz.open(stream=pdf):
             yield page.get_pixmap().tobytes("png"), metadata
 
-    if item_type == "string":
-        operation = upper
-    elif item_type == "image":
-        operation = rotate
-    elif item_type == "pdf":
-        operation = stream_pages
-    else:
+    try:
+        return {"string": upper, "image": rotate, "pdf": stream_pages}[item_type]
+    except KeyError:
         raise ValueError(f"No operation specified for item type {item_type}")
 
-    return operation
-
 
 @pytest.fixture(params=["string"])
 def item_type(request):
     return request.param
 
 
-@pytest.fixture(params=[False])
+@pytest.fixture(params=[False, True])
 def batched(request):
     """Controls, whether the buffer processor function of the webserver is applied to batches or single items."""
     return request.param