[test] the templates example (#3269)

Cargo.lock

@@ -1814,7 +1814,9 @@ version = "0.1.0"
 dependencies = [
  "askama",
  "axum",
+ "http-body-util",
  "tokio",
+ "tower 0.5.2",
  "tracing",
  "tracing-subscriber",
 ]

examples/templates/Cargo.toml

@@ -10,3 +10,7 @@ axum = { path = "../../axum" }
 tokio = { version = "1.0", features = ["full"] }
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+
+[dev-dependencies]
+http-body-util = "0.1.0"
+tower = { version = "0.5.2", features = ["util"] }

examples/templates/src/main.rs

@@ -25,7 +25,7 @@ async fn main() {
         .init();
 
     // build our application with some routes
-    let app = Router::new().route("/greet/{name}", get(greet));
+    let app = app();
 
     // run it
     let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
@@ -35,6 +35,10 @@ async fn main() {
     axum::serve(listener, app).await.unwrap();
 }
 
+fn app() -> Router {
+    Router::new().route("/greet/{name}", get(greet))
+}
+
 async fn greet(extract::Path(name): extract::Path<String>) -> impl IntoResponse {
     let template = HelloTemplate { name };
     HtmlTemplate(template)
@@ -63,3 +67,33 @@ where
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use axum::{
+        body::Body,
+        http::{Request, StatusCode},
+    };
+    use http_body_util::BodyExt;
+    use tower::ServiceExt;
+
+    #[tokio::test]
+    async fn test_main() {
+        let response = app()
+            .oneshot(
+                Request::builder()
+                    .uri("/greet/Foo")
+                    .body(Body::empty())
+                    .unwrap(),
+            )
+            .await
+            .unwrap();
+        assert_eq!(response.status(), StatusCode::OK);
+        let body = response.into_body();
+        let bytes = body.collect().await.unwrap().to_bytes();
+        let html = String::from_utf8(bytes.to_vec()).unwrap();
+
+        assert_eq!(html, "<h1>Hello, Foo!</h1>");
+    }
+}