type driven development, checks for email + name

tests/health_check.rs

@@ -132,3 +132,32 @@ async fn subscribe_returns_a_400_when_data_is_missing() {
         );
     }
 }
+
+#[tokio::test]
+async fn subscribe_returns_a_400_when_fields_are_present_but_invalid() {
+	let app = spawn_app().await;
+	let client = reqwest::Client::new();
+	let test_cases = vec![
+		("name=&email=ursula_le_guin%40gmail.com", "name is empty"),
+		("name=le%20guin&email=", "email is empty"),
+		("name=&email=", "name and email are empty"),
+		("name=Ursula&email=definitely-not-an-email", "invalid email"),
+	];
+
+	for (invalid_body, error_message) in test_cases {
+		let response = client
+			.post(&format!("{}/subscriptions", &app.address))
+			.header("Content-Type", "application/x-www-form-urlencoded")
+			.body(invalid_body)
+			.send()
+			.await
+			.expect("Failed to execute request.");
+
+		assert_eq!(
+			400,
+			response.status().as_u16(),
+			"The API did not return a 400 Bad Request when the payload was {}.",
+			error_message
+		);
+	}
+}