Add an example integration test for SSE (#2465)

Signed-off-by: Hung-Han (Henry) Chen <chenhungh@gmail.com>
Co-authored-by: David Pedersen <david.pdrsn@gmail.com>

examples/sse/Cargo.toml

@@ -14,3 +14,8 @@ tokio-stream = "0.1"
 tower-http = { version = "0.5.0", features = ["fs", "trace"] }
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+
+[dev-dependencies]
+eventsource-stream = "0.2"
+reqwest = { version = "0.11", features = ["stream"] }
+reqwest-eventsource = "0.5"

examples/sse/src/main.rs

@@ -3,6 +3,10 @@
 //! ```not_rust
 //! cargo run -p example-sse
 //! ```
+//! Test with
+//! ```not_rust
+//! cargo test -p example-sse
+//! ```
 
 use axum::{
     response::sse::{Event, Sse},
@@ -26,15 +30,8 @@ async fn main() {
         .with(tracing_subscriber::fmt::layer())
         .init();
 
-    let assets_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("assets");
-
-    let static_files_service = ServeDir::new(assets_dir).append_index_html_on_directories(true);
-
-    // build our application with a route
-    let app = Router::new()
-        .fallback_service(static_files_service)
-        .route("/sse", get(sse_handler))
-        .layer(TraceLayer::new_for_http());
+    // build our application
+    let app = app();
 
     // run it
     let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
@@ -44,6 +41,16 @@ async fn main() {
     axum::serve(listener, app).await.unwrap();
 }
 
+fn app() -> Router {
+    let assets_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("assets");
+    let static_files_service = ServeDir::new(assets_dir).append_index_html_on_directories(true);
+    // build our application with a route
+    Router::new()
+        .fallback_service(static_files_service)
+        .route("/sse", get(sse_handler))
+        .layer(TraceLayer::new_for_http())
+}
+
 async fn sse_handler(
     TypedHeader(user_agent): TypedHeader<headers::UserAgent>,
 ) -> Sse<impl Stream<Item = Result<Event, Infallible>>> {
@@ -63,3 +70,58 @@ async fn sse_handler(
             .text("keep-alive-text"),
     )
 }
+
+#[cfg(test)]
+mod tests {
+    use eventsource_stream::Eventsource;
+    use tokio::net::TcpListener;
+
+    use super::*;
+
+    #[tokio::test]
+    async fn integration_test() {
+        // A helper function that spawns our application in the background
+        async fn spawn_app(host: impl Into<String>) -> String {
+            let host = host.into();
+            // Bind to localhost at the port 0, which will let the OS assign an available port to us
+            let listener = TcpListener::bind(format!("{}:0", host)).await.unwrap();
+            // Retrieve the port assigned to us by the OS
+            let port = listener.local_addr().unwrap().port();
+            tokio::spawn(async {
+                axum::serve(listener, app()).await.unwrap();
+            });
+            // Returns address (e.g. http://127.0.0.1{random_port})
+            format!("http://{}:{}", host, port)
+        }
+        let listening_url = spawn_app("127.0.0.1").await;
+
+        let mut event_stream = reqwest::Client::new()
+            .get(&format!("{}/sse", listening_url))
+            .header("User-Agent", "integration_test")
+            .send()
+            .await
+            .unwrap()
+            .bytes_stream()
+            .eventsource()
+            .take(1);
+
+        let mut event_data: Vec<String> = vec![];
+        while let Some(event) = event_stream.next().await {
+            match event {
+                Ok(event) => {
+                    // break the loop at the end of SSE stream
+                    if event.data == "[DONE]" {
+                        break;
+                    }
+
+                    event_data.push(event.data);
+                }
+                Err(_) => {
+                    panic!("Error in event stream");
+                }
+            }
+        }
+
+        assert!(event_data[0] == "hi!");
+    }
+}