template reload: simplest test of a single template reload cycle

contrib/tests/templates.rs

@@ -67,5 +67,46 @@ mod handlebars_tests {
         let template = Template::show(&rocket, "hbs/test", &map);
         assert_eq!(template, Some(EXPECTED.into()));
     }
+
+    #[cfg(debug_assertions)]
+    #[test]
+    fn test_template_reload() {
+        use rocket::local::Client;
+        use std::fs::{File, remove_file};
+        use std::io::Write;
+        use std::path::Path;
+
+        fn write_file(path: &Path, text: &str) {
+            let mut file = File::create(path).expect("open file");
+            file.write_all(text.as_bytes()).expect("write file");
+        }
+
+        const RELOAD_TEMPLATE: &'static str = "hbs/reload";
+        const INITIAL_TEXT: &'static str = "initial";
+        const NEW_TEXT: &'static str = "reload";
+
+        let reload_path = Path::join(
+            Path::new(env!("CARGO_MANIFEST_DIR")),
+            "tests/templates/hbs/reload.txt.hbs"
+        );
+
+        write_file(&reload_path, INITIAL_TEXT);
+
+        let client = Client::new(rocket()).unwrap();
+
+        // verify that the initial content is correct
+        let initial_rendered = Template::show(client.rocket(), RELOAD_TEMPLATE, ());
+        assert_eq!(initial_rendered, Some(INITIAL_TEXT.into()));
+
+        // write to the file, then dispatch any request to trigger template reload
+        write_file(&reload_path, NEW_TEXT);
+        client.get("/").dispatch();
+
+        // verify that the new content is correct
+        let new_rendered = Template::show(client.rocket(), RELOAD_TEMPLATE, ());
+        assert_eq!(new_rendered, Some(NEW_TEXT.into()));
+
+        remove_file(reload_path).expect("delete template file");
+    }
 }