diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 04508a3..ba8e250 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,5 +1,9 @@
 name: Rust CI
-on: [push]
+on:
+  push:
+  pull_request:
+    types: [opened, repoened, synchronize]
+
 jobs:
   combo:
     name: test + Clippy + rustfmt
diff --git a/src/opaque.rs b/src/opaque.rs
index 86797ad..42a27b3 100644
--- a/src/opaque.rs
+++ b/src/opaque.rs
@@ -113,10 +113,11 @@ where
     KeyFormat: KeyPair,
 {
     pub fn to_bytes(&self) -> Vec<u8> {
-        let mut res = Vec::new();
-        res.extend(self.envelope.to_bytes());
-        res.extend(self.client_s_pk.to_arr());
-        res
+        [
+            &self.envelope.to_bytes(),
+            self.client_s_pk.to_arr().as_slice(),
+        ]
+        .concat()
     }
 }
 
@@ -165,12 +166,11 @@ impl<Grp: Group> TryFrom<&[u8]> for LoginFirstMessage<Grp> {
 
 impl<Grp: Group> LoginFirstMessage<Grp> {
     pub fn to_bytes(&self) -> Vec<u8> {
-        let output: Vec<u8> = [
+        [
             self.alpha.to_bytes().as_slice(),
             &self.ke1_message.to_bytes(),
         ]
-        .concat();
-        output
+        .concat()
     }
 }
 
diff --git a/src/tests/serialization.rs b/src/tests/serialization.rs
index cf1766c..59dcb22 100644
--- a/src/tests/serialization.rs
+++ b/src/tests/serialization.rs
@@ -29,9 +29,7 @@ fn client_registration_roundtrip() {
     let mut rng = OsRng;
     let sc = <RistrettoPoint as Group>::random_scalar(&mut rng);
     // serialization order: scalar, password
-    let mut bytes: Vec<u8> = vec![];
-    bytes.extend_from_slice(sc.as_bytes());
-    bytes.extend_from_slice(pw);
+    let bytes: Vec<u8> = [&sc.as_bytes()[..], &pw[..]].concat();
     let reg = ClientRegistration::<ChaCha20Poly1305, RistrettoPoint>::try_from(&bytes[..]).unwrap();
     let reg_bytes = reg.to_bytes();
     assert_eq!(reg_bytes, bytes);
@@ -113,10 +111,7 @@ fn register_third_message_roundtrip() {
     )
     .unwrap();
 
-    let mut message = Vec::new();
-    message.extend_from_slice(&ciphertext.to_bytes());
-    message.extend_from_slice(&pubkey_bytes);
-
+    let message: Vec<u8> = [&ciphertext.to_bytes(), &pubkey_bytes[..]].concat();
     let r3 =
         RegisterThirdMessage::<ChaCha20Poly1305, SignalKeyPair>::try_from(&message[..]).unwrap();
     let r3_bytes = r3.to_bytes();