diff --git a/services/commtest/tests/lib/tools.rs b/services/commtest/tests/lib/tools.rs
--- a/services/commtest/tests/lib/tools.rs
+++ b/services/commtest/tests/lib/tools.rs
@@ -24,5 +24,13 @@
   TonicStatus(tonic::Status),
 }
 
+#[allow(dead_code)]
+pub const GRPC_METADATA_SIZE: usize = 5;
+
+#[allow(dead_code)]
+pub fn get_grpc_chunk_size_limit() -> usize {
+  (ByteSize::mib(4).as_u64() as usize) - GRPC_METADATA_SIZE
+}
+
 #[allow(dead_code)]
 pub const ATTACHMENT_DELIMITER: char = ';';