diff --git a/elfo-test/Cargo.toml b/elfo-test/Cargo.toml
index b30a4641..a8e5d700 100644
--- a/elfo-test/Cargo.toml
+++ b/elfo-test/Cargo.toml
@@ -21,3 +21,4 @@ futures-intrusive = "0.5"
 futures = "0.3.12"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 once_cell = { version = "1.8.0" }
+stability = "0.1.1"
diff --git a/elfo-test/src/expect.rs b/elfo-test/src/expect.rs
new file mode 100644
index 00000000..277b1c7a
--- /dev/null
+++ b/elfo-test/src/expect.rs
@@ -0,0 +1,25 @@
+use elfo_core::{dumping::extract_name_by_type, msg, Envelope, Message, Request, ResponseToken};
+
+#[track_caller]
+pub fn expect_message<T: Message>(msg: Envelope) -> T {
+    msg!(match msg {
+        msg @ T => msg,
+        msg => panic!(
+            r#"unexpected message: expected "{}", got "{}""#,
+            extract_name_by_type::<T>(),
+            msg.message().name()
+        ),
+    })
+}
+
+#[track_caller]
+pub fn expect_request<T: Request>(msg: Envelope) -> (T, ResponseToken<T>) {
+    msg!(match msg {
+        (msg @ T, token) => (msg, token),
+        msg => panic!(
+            r#"unexpected request: expected "{}", got "{}""#,
+            extract_name_by_type::<T>(),
+            msg.message().name()
+        ),
+    })
+}
diff --git a/elfo-test/src/lib.rs b/elfo-test/src/lib.rs
index 19d7cded..03959656 100644
--- a/elfo-test/src/lib.rs
+++ b/elfo-test/src/lib.rs
@@ -1,5 +1,10 @@
 #![warn(rust_2018_idioms, unreachable_pub)]
 
+pub use expect::{expect_message, expect_request};
 pub use proxy::{proxy, Proxy};
 
+#[cfg(feature = "unstable")]
+pub use proxy::proxy_with_route;
+
+mod expect;
 mod proxy;
diff --git a/elfo-test/src/proxy.rs b/elfo-test/src/proxy.rs
index 594a433f..af1c42e9 100644
--- a/elfo-test/src/proxy.rs
+++ b/elfo-test/src/proxy.rs
@@ -224,7 +224,16 @@ fn testers(tx: shared::OneshotSender<ProxyContext>) -> Blueprint {
         })
 }
 
-pub async fn proxy(blueprint: Blueprint, config: impl for<'de> Deserializer<'de>) -> Proxy {
+#[doc(hidden)]
+#[stability::unstable]
+pub async fn proxy_with_route<F>(
+    blueprint: Blueprint,
+    route_filter: F,
+    config: impl for<'de> Deserializer<'de>,
+) -> Proxy
+where
+    F: Fn(&Envelope) -> bool + Send + Sync + 'static,
+{
     let _ = tracing_subscriber::fmt()
         .with_target(false)
         .with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
@@ -244,7 +253,7 @@ pub async fn proxy(blueprint: Blueprint, config: impl for<'de> Deserializer<'de>
     let subject_addr = subject.addr();
 
     testers.route_all_to(&subject);
-    subject.route_all_to(&testers);
+    subject.route_to(&testers, route_filter);
 
     // TODO: capture log messages.
     // TODO: capture metrics.
@@ -271,6 +280,10 @@ pub async fn proxy(blueprint: Blueprint, config: impl for<'de> Deserializer<'de>
     }
 }
 
+pub async fn proxy(blueprint: Blueprint, config: impl for<'de> Deserializer<'de>) -> Proxy {
+    proxy_with_route(blueprint, |_| true, config).await
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;