chore(all): Add back test for smtp pool

tests/transport_smtp_pool.rs

@@ -0,0 +1,61 @@
+#[cfg(all(test, feature = "smtp-transport", feature = "r2d2"))]
+mod test {
+    use lettre::{Envelope, SmtpTransport, Tls, Transport};
+    use r2d2::Pool;
+    use std::{sync::mpsc, thread};
+
+    fn envelope() -> Envelope {
+        Envelope::new(
+            Some("user@localhost".parse().unwrap()),
+            vec!["root@localhost".parse().unwrap()],
+        )
+        .unwrap()
+    }
+
+    #[test]
+    fn send_one() {
+        let client = SmtpTransport::new("127.0.0.1").port(2525);
+        let c = client.clone();
+        let pool = Pool::builder().max_size(1).build(c).unwrap();
+        let mailer = client.pool(pool);
+
+        let result = mailer.send_raw(&envelope(), b"test");
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn send_from_thread() {
+        let client = SmtpTransport::new("127.0.0.1").port(2525);
+        let c = client.clone();
+        let pool = Pool::builder().max_size(1).build(c).unwrap();
+        let mailer = client.pool(pool);
+
+        let (s1, r1) = mpsc::channel();
+        let (s2, r2) = mpsc::channel();
+
+        let mailer1 = mailer.clone();
+        let t1 = thread::spawn(move || {
+            s1.send(()).unwrap();
+            r2.recv().unwrap();
+            mailer1
+                .send_raw(&envelope(), b"test1")
+                .expect("Send failed from thread 1");
+        });
+
+        let mailer2 = mailer.clone();
+        let t2 = thread::spawn(move || {
+            s2.send(()).unwrap();
+            r1.recv().unwrap();
+            mailer2
+                .send_raw(&envelope(), b"test2")
+                .expect("Send failed from thread 2");
+        });
+
+        t1.join().unwrap();
+        t2.join().unwrap();
+
+        mailer
+            .send_raw(&envelope(), b"test")
+            .expect("Send failed from main thread");
+    }
+}