[test] the hello-world example

See tokio-rs#3263

Author: szabgab

examples/hello-world/src/main.rs

@@ -22,3 +22,16 @@ async fn main() {
 async fn handler() -> Html<&'static str> {
     Html("<h1>Hello, World!</h1>")
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use axum::response::Html;
+
+    #[tokio::test]
+    async fn test_handler() {
+        let response = handler().await;
+        let Html(content) = response;
+        assert_eq!(content, "<h1>Hello, World!</h1>");
+    }
+}