diff --git a/pyinfra/rest.py b/pyinfra/rest.py
index 2bb799e..0d2f715 100644
--- a/pyinfra/rest.py
+++ b/pyinfra/rest.py
@@ -89,7 +89,7 @@ def post_partial(url, data: Iterable[bytes], metadata: dict):
         dispatch_http_method_left_and_forward_data_right,
         send_data_with_method_to_analyzer,
         extract_payload_from_responses,
-        flatten,  # analysis may be 1 -> 1 or 1 -> n, so flatten
+        flatten,  # each analysis call returns an iterable. Can be empty, singleton or multi item. Hence, flatten.
     )
 
     return input_data_to_result_data(data)
diff --git a/test/exploration_tests/partial_response_test.py b/test/exploration_tests/partial_response_test.py
index bcdcbdc..af8747c 100644
--- a/test/exploration_tests/partial_response_test.py
+++ b/test/exploration_tests/partial_response_test.py
@@ -1,10 +1,11 @@
 import pytest
+from funcy import lmap
 
-from pyinfra.rest import post_partial
+from pyinfra.rest import post_partial, unpack
 
 
 @pytest.mark.parametrize("batched", [True, False])
 @pytest.mark.parametrize("item_type", ["pdf", "string", "image"])
 def test_sending_partial_request(url, input_data_items, metadata, operation, target_data_items, server_process):
-    output = list(post_partial(f"{url}/process", input_data_items, metadata))
-    assert output == target_data_items
+    output = lmap(unpack, post_partial(f"{url}/process", input_data_items, metadata))
+    assert output == lmap(unpack, target_data_items)
diff --git a/test/fixtures/input.py b/test/fixtures/input.py
index d8e3308..92c64d5 100644
--- a/test/fixtures/input.py
+++ b/test/fixtures/input.py
@@ -37,7 +37,7 @@ def target_data_items(input_data_items, item_type, operation, metadata):
     return expected
 
 
-@pytest.fixture(params=[0, 1, 2, 5])
+@pytest.fixture(params=[0, 1, 2, 5, 10])
 def n_items(request):
     return request.param
 
@@ -50,10 +50,15 @@ def input_batch(n_items):
     return np.random.random_sample(size=(n_items, 3, 30, 30))
 
 
+@pytest.fixture(params=[1, 2, 5, 100])
+def buffer_size(request):
+    return request.param
+
+
 def images(n_items):
     return lmap(compose(image_to_bytes, array_to_image), input_batch(n_items))
 
 
 @pytest.fixture
 def metadata():
-    return {"idx": [1, 100, 101], "path": "asd/asd"}
+    return {"dummy": True}
diff --git a/test/fixtures/pdf.py b/test/fixtures/pdf.py
index 82c6e77..7d16f09 100644
--- a/test/fixtures/pdf.py
+++ b/test/fixtures/pdf.py
@@ -8,5 +8,6 @@ from test.utils.pdf import pdf_stream
 def pdf():
     pdf = fpdf.FPDF(unit="pt")
     pdf.add_page()
+    pdf.add_page()
 
     return pdf_stream(pdf)
diff --git a/test/fixtures/server.py b/test/fixtures/server.py
index 64f4c2b..5c66599 100644
--- a/test/fixtures/server.py
+++ b/test/fixtures/server.py
@@ -65,8 +65,9 @@ def operation(item_type, batched):
         return image_to_bytes(im.rotate(90)), metadata
 
     def stream_pages(pdf: bytes, metadata):
-        for page in fitz.open(stream=pdf):
-            yield page.get_pixmap().tobytes("png"), metadata
+        for i, page in enumerate(fitz.open(stream=pdf)):
+            # yield page.get_pixmap().tobytes("png"), metadata
+            yield f"page_{i}".encode(), metadata
 
     try:
         return {"string": upper, "image": rotate, "pdf": stream_pages}[item_type]
@@ -85,11 +86,6 @@ def batched(request):
     return request.param
 
 
-@pytest.fixture(params=[1, 3, 7, 100])
-def buffer_size(request):
-    return request.param
-
-
 @pytest.fixture
 def host_and_port(host, port):
     return {"host": host, "port": port}