feat: subscribe API route skeleton

- Added `serde` crate for serialisation or deserialisation of data
- Added test cases for the `subscribe` API route
- Refactor the testing setup to another module `test_utils`
- use random TCP port for testing

tests/README.md

@@ -0,0 +1,5 @@
+# Tests
+
+## Notes
+
+`tokio` spins up a new async runtime every time at the beginning of each test case and shutdown at the end of each test case the `spawn_app()` function therefore only survives as long as the runtime.

tests/health_check.rs

@@ -1,32 +1,19 @@
-use std::{fmt::format, net::TcpListener};
-// tokio spins up a new async runtime every time 
-// at the beginning of each test case and shutdown at
-// the end of each test case
-// the spawn_app() function therefore only survives as long as the runtime
+mod test_utils;
+
+use test_utils::spawn_app;
+
 #[tokio::test]
-async fn health_check_works(){
+async fn health_check_works() {
     let server_address = spawn_app();
 
     let client = reqwest::Client::new();
 
-    let response = client.get(&format!("{}/health_check", &server_address)).send().await.expect("Failed to execute health_check request.");
+    let response = client
+        .get(&format!("{}/health_check", &server_address))
+        .send()
+        .await
+        .expect("Failed to execute health_check request.");
 
     assert!(response.status().is_success());
     assert_eq!(Some(0), response.content_length());
 }
-
-fn spawn_app() -> String {
-    let listener = TcpListener::bind("127.0.0.1:0").expect("Failed to bind to a random port");
-
-    let port = listener.local_addr().unwrap().port();
-
-    let server = email_newsletter_api::run(listener).expect("Failed to bind address");
-
-    // run() returns an instance of HttpServer that will run forever.
-    // We don't want this behavior
-    // Therefore we want to spawn our server, run our test logic
-    // and then tear down the entire test suite
-    let _ = tokio::spawn(server);
-
-    format!("http://127.0.0.1:{}", port)
-}

tests/subscribe.rs

@@ -0,0 +1,53 @@
+mod test_utils;
+
+use test_utils::spawn_app;
+
+#[tokio::test]
+async fn subscribe_returns_a_200_for_valid_form_data() {
+    let server_address = spawn_app();
+
+    let client = reqwest::Client::new();
+
+    let body = "name=le%20test&email=le_test%40gmail.com";
+
+    let response = client
+        .post(&format!("{}/subscribe", &server_address))
+        .header("Content-Type", "application/x-www-form-urlencoded")
+        .body(body)
+        .send()
+        .await
+        .expect("Failed to execute subscribe request.");
+
+    assert!(response.status().is_success());
+    assert_eq!(Some(0), response.content_length());
+}
+
+#[tokio::test]
+async fn subscribe_returns_a_400_when_data_is_missing() {
+    let server_address = spawn_app();
+
+    let client = reqwest::Client::new();
+
+    let test_cases = vec![
+        ("name=le%20guin", "missing the email"),
+        ("email=ursula_le_guin%40gmail.com", "missing the name"),
+        ("", "missing both name and email"),
+    ];
+
+    for (invalid_body, error_message) in test_cases {
+        let response = client
+            .post(&format!("{}/subscribe", &server_address))
+            .header("Content-Type", "application/x-www-form-urlencoded")
+            .body(invalid_body)
+            .send()
+            .await
+            .expect("Failed to execute subscribe request.");
+
+        assert_eq!(
+            400,
+            response.status().as_u16(),
+            "The API failed with 400 Bad Request when the payload was {}.",
+            error_message
+        )
+    }
+}

tests/test_utils.rs

@@ -0,0 +1,24 @@
+use std::net::TcpListener;
+
+#[allow(dead_code)]
+#[allow(clippy::let_underscore_future)]
+pub fn spawn_app() -> String {
+    /* Spawn a app server with a TcpListener bound to localhost:<random port>
+     *
+     *  Returns a valid IPv4 string (i.e localhost:8080)
+     */
+    let listener = TcpListener::bind("127.0.0.1:0").expect("Failed to bind to a random port");
+
+    let port = listener.local_addr().unwrap().port();
+
+    let server = email_newsletter_api::run(listener).expect("Failed to bind address");
+
+    /* `tokio::spawn(/*async task*/)` will spawn an async task to be run.
+    We can continue executing other code concurrently while `task` runs in the background.
+    If we need to wait for `task` to complete before proceeding,
+    we can use `task.await`
+    (which `#[tokio::test]` will take care for us in the mean time).*/
+    let _ = tokio::spawn(server);
+
+    format!("http://127.0.0.1:{}", port)
+}