diff --git a/test/test_serialization.py b/test/test_serialization.py
index d1bfc66..d6a9bb3 100644
--- a/test/test_serialization.py
+++ b/test/test_serialization.py
@@ -57,8 +57,11 @@ def test_roundtrip_file_multiple(all_types):
     msg.write(f)
 
     f.seek(0)
+    i = 0
     for msg in all_types.TestAllTypes.read_multiple(f):
         test_regression.check_all_types(msg)
+        i += 1
+    assert i == 3
 
 def test_roundtrip_bytes_multiple(all_types):
     msg = all_types.TestAllTypes.new_message()
@@ -68,8 +71,11 @@ def test_roundtrip_bytes_multiple(all_types):
     msgs += msg.to_bytes()
     msgs += msg.to_bytes()
 
+    i = 0
     for msg in all_types.TestAllTypes.read_multiple_bytes(msgs):
         test_regression.check_all_types(msg)
+        i += 1
+    assert i == 3
 
 def test_roundtrip_file_multiple_packed(all_types):
     f = tempfile.TemporaryFile()
@@ -80,8 +86,11 @@ def test_roundtrip_file_multiple_packed(all_types):
     msg.write_packed(f)
 
     f.seek(0)
+    i = 0
     for msg in all_types.TestAllTypes.read_multiple_packed(f):
         test_regression.check_all_types(msg)
+        i += 1
+    assert i == 3
 
 def test_roundtrip_bytes_multiple_packed(all_types):
     msg = all_types.TestAllTypes.new_message()
@@ -91,8 +100,11 @@ def test_roundtrip_bytes_multiple_packed(all_types):
     msgs += msg.to_bytes_packed()
     msgs += msg.to_bytes_packed()
 
+    i = 0
     for msg in all_types.TestAllTypes.read_multiple_bytes_packed(msgs):
         test_regression.check_all_types(msg)
+        i += 1
+    assert i == 3
 
 def test_roundtrip_dict(all_types):
     msg = all_types.TestAllTypes.new_message()