diff --git a/services/commtest/tests/lib/tools.rs b/services/commtest/tests/lib/tools.rs
new file mode 100644
--- /dev/null
+++ b/services/commtest/tests/lib/tools.rs
@@ -0,0 +1,25 @@
+use bytesize::ByteSize;
+use std::env;
+
+#[allow(dead_code)]
+pub fn generate_nbytes(n: usize, c: Option<u8>) -> Vec<u8> {
+  let c: u8 = match c {
+    Some(c) => c,
+    None => b'A',
+  };
+  return vec![c; n];
+}
+
+#[derive(
+  Debug, derive_more::Display, derive_more::From, derive_more::Error,
+)]
+pub enum Error {
+  #[display(...)]
+  EnvVar(env::VarError),
+  #[display(...)]
+  Proto(std::io::Error),
+  #[display(...)]
+  Tonic(tonic::transport::Error),
+  #[display(...)]
+  TonicStatus(tonic::Status),
+}