diff --git a/proto/src/core/mod.rs b/proto/src/core/mod.rs
index 02782ed..2137cde 100644
--- a/proto/src/core/mod.rs
+++ b/proto/src/core/mod.rs
@@ -1,12 +1,16 @@
 mod frame;
 mod prefix;
+#[cfg(test)]
+pub mod testing;
 mod u32;
 mod user;
-// TODO: Remove `pub` qualifier, depend on re-exports.
-pub mod value;
+mod value;
 mod worker;
 
 pub use frame::{FrameReader, FrameWriter};
 pub use user::{User, UserStatus};
-pub use value::{ValueDecode, ValueEncode};
+pub use value::{
+  ValueDecode, ValueDecodeError, ValueDecoder, ValueEncode, ValueEncodeError,
+  ValueEncoder,
+};
 pub use worker::{Worker, WorkerError};
diff --git a/proto/src/core/testing.rs b/proto/src/core/testing.rs
new file mode 100644
index 0000000..4415977
--- /dev/null
+++ b/proto/src/core/testing.rs
@@ -0,0 +1,20 @@
+//! Shared testing utilities for protocol code.
+
+use std::fmt;
+
+use bytes::BytesMut;
+
+use crate::core::{ValueDecode, ValueDecoder, ValueEncode, ValueEncoder};
+
+/// Encodes `input`, decodes it, asserts equality of `input` and the result.
+pub fn roundtrip<T>(input: T)
+where
+  T: fmt::Debug + Eq + PartialEq + ValueEncode + ValueDecode,
+{
+  let mut bytes = BytesMut::new();
+
+  ValueEncoder::new(&mut bytes).encode(&input).unwrap();
+  let output = ValueDecoder::new(&bytes).decode::<T>().unwrap();
+
+  assert_eq!(output, input);
+}
diff --git a/proto/src/core/value.rs b/proto/src/core/value.rs
index bf585a3..1b6c0bf 100644
--- a/proto/src/core/value.rs
+++ b/proto/src/core/value.rs
@@ -506,32 +506,19 @@ impl<T: ValueEncode> ValueEncode for Vec<T> {
 
 #[cfg(test)]
 pub mod tests {
-  use std::fmt;
   use std::net;
   use std::u16;
   use std::u32;
 
   use bytes::{BufMut, BytesMut};
 
-  use super::{
-    ValueDecode, ValueDecodeError, ValueDecoder, ValueEncode, ValueEncoder,
-  };
+  use crate::core::testing::roundtrip;
+
+  use super::{ValueDecodeError, ValueDecoder, ValueEncoder};
 
   // Declared here because assert_eq!(bytes, &[]) fails to infer types.
   const EMPTY_BYTES: &'static [u8] = &[];
 
-  pub fn roundtrip<T>(input: T)
-  where
-    T: fmt::Debug + Eq + PartialEq + ValueEncode + ValueDecode,
-  {
-    let mut bytes = BytesMut::new();
-
-    ValueEncoder::new(&mut bytes).encode(&input).unwrap();
-    let output = ValueDecoder::new(&bytes).decode::<T>().unwrap();
-
-    assert_eq!(output, input);
-  }
-
   // A few integers and their corresponding byte encodings.
   const U32_ENCODINGS: [(u32, [u8; 4]); 8] = [
     (0, [0, 0, 0, 0]),
diff --git a/proto/src/core/worker.rs b/proto/src/core/worker.rs
index 124685c..ad344fd 100644
--- a/proto/src/core/worker.rs
+++ b/proto/src/core/worker.rs
@@ -7,8 +7,8 @@ use tokio::net::tcp::{OwnedReadHalf, OwnedWriteHalf};
 use tokio::net::TcpStream;
 use tokio::sync::mpsc;
 
-use crate::core::{FrameReader, FrameWriter};
 use crate::core::value::{ValueDecode, ValueEncode};
+use crate::core::{FrameReader, FrameWriter};
 
 /// An error that arose while exchanging messages over a `Channel`.
 #[derive(Debug, Error)]
diff --git a/proto/src/peer/message.rs b/proto/src/peer/message.rs
index 55bfac7..6d4f916 100644
--- a/proto/src/peer/message.rs
+++ b/proto/src/peer/message.rs
@@ -1,4 +1,4 @@
-use crate::core::value::{
+use crate::core::{
   ValueDecode, ValueDecodeError, ValueDecoder, ValueEncode, ValueEncodeError,
   ValueEncoder,
 };
@@ -99,8 +99,8 @@ impl ValueDecode for PeerInit {
 mod tests {
   use bytes::BytesMut;
 
-  use crate::core::value::tests::roundtrip;
-  use crate::core::value::{ValueDecodeError, ValueDecoder};
+  use crate::core::testing::roundtrip;
+  use crate::core::{ValueDecodeError, ValueDecoder};
 
   use super::*;
 
diff --git a/proto/src/server/request.rs b/proto/src/server/request.rs
index a8cdc07..59c6729 100644
--- a/proto/src/server/request.rs
+++ b/proto/src/server/request.rs
@@ -1,4 +1,4 @@
-use crate::core::value::{
+use crate::core::{
   ValueDecode, ValueDecodeError, ValueDecoder, ValueEncode, ValueEncodeError,
   ValueEncoder,
 };
@@ -496,8 +496,8 @@ impl ValueDecode for UserStatusRequest {
 mod tests {
   use bytes::BytesMut;
 
-  use crate::core::value::tests::roundtrip;
-  use crate::core::value::{ValueDecodeError, ValueDecoder};
+  use crate::core::testing::roundtrip;
+  use crate::core::{ValueDecodeError, ValueDecoder};
 
   use super::*;
 
diff --git a/proto/src/server/response.rs b/proto/src/server/response.rs
index 8d72c69..ccb6a13 100644
--- a/proto/src/server/response.rs
+++ b/proto/src/server/response.rs
@@ -2,7 +2,7 @@ use std::net;
 
 use log::{debug, warn};
 
-use crate::core::value::{
+use crate::core::{
   ValueDecode, ValueDecodeError, ValueDecoder, ValueEncode, ValueEncodeError,
   ValueEncoder,
 };
@@ -1118,8 +1118,8 @@ mod tests {
 
   use bytes::BytesMut;
 
-  use crate::core::value::tests::roundtrip;
-  use crate::core::value::{ValueDecodeError, ValueDecoder};
+  use crate::core::testing::roundtrip;
+  use crate::core::{ValueDecodeError, ValueDecoder};
 
   use super::*;