Merge #785: Rearrange tests for XOnlyPublicKey::from_slice

a4cb345 Reposition test_pubkey_from_bad_slice, and move failing cases from test_pubkey_from_slice (Salvatore Ingala)

Pull request description:

  Adds two test cases for parsing an invalid key (despite it being 32-byte long).

  Perhaps the test for `ZERO` is redundant, as `7` also has no square root, but it felt natural to add it anyway.

ACKs for top commit:
  apoelstra:
    ACK a4cb345; successfully ran local tests; yeah, sure. I think this makes the tests a bit easier to follow

Tree-SHA512: f5f7f3c175c65bd9f1bb589e18246c9155d8cbed2f43ff425757222cb64fe2ec6b0e793cef500ff3e20d33135c7065fe5a835c3f4693d1b801f71fe36db25a8d

Author: apoelstra

src/schnorr.rs

@@ -318,8 +318,6 @@ mod tests {
 
     #[test]
     fn test_pubkey_from_slice() {
-        assert_eq!(XOnlyPublicKey::from_slice(&[]), Err(InvalidPublicKey));
-        assert_eq!(XOnlyPublicKey::from_slice(&[1, 2, 3]), Err(InvalidPublicKey));
         let pk = XOnlyPublicKey::from_slice(&[
             0xB3, 0x3C, 0xC9, 0xED, 0xC0, 0x96, 0xD0, 0xA8, 0x34, 0x16, 0x96, 0x4B, 0xD3, 0xC6,
             0x24, 0x7B, 0x8F, 0xEC, 0xD2, 0x56, 0xE4, 0xEF, 0xA7, 0x87, 0x0D, 0x2C, 0x85, 0x4B,
@@ -328,35 +326,11 @@ mod tests {
         assert!(pk.is_ok());
     }
 
-    #[test]
-    #[cfg(all(feature = "rand", feature = "std"))]
-    fn test_pubkey_serialize_roundtrip() {
-        let secp = Secp256k1::new();
-        let kp = Keypair::new(&secp, &mut rand::thread_rng());
-        let (pk, _parity) = kp.x_only_public_key();
-
-        let ser = pk.serialize();
-        let pubkey2 = XOnlyPublicKey::from_slice(&ser).unwrap();
-        assert_eq!(pk, pubkey2);
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    fn test_xonly_key_extraction() {
-        let secp = Secp256k1::new();
-        let sk_str = "688C77BC2D5AAFF5491CF309D4753B732135470D05B7B2CD21ADD0744FE97BEF";
-        let keypair = Keypair::from_seckey_str(&secp, sk_str).unwrap();
-        let sk = SecretKey::from_keypair(&keypair);
-        assert_eq!(SecretKey::from_str(sk_str).unwrap(), sk);
-        let pk = crate::key::PublicKey::from_keypair(&keypair);
-        assert_eq!(crate::key::PublicKey::from_secret_key(&secp, &sk), pk);
-        let (xpk, _parity) = keypair.x_only_public_key();
-        assert_eq!(XOnlyPublicKey::from(pk), xpk);
-    }
-
     #[test]
     fn test_pubkey_from_bad_slice() {
         // Bad sizes
+        assert_eq!(XOnlyPublicKey::from_slice(&[]), Err(InvalidPublicKey));
+        assert_eq!(XOnlyPublicKey::from_slice(&[1, 2, 3]), Err(InvalidPublicKey));
         assert_eq!(
             XOnlyPublicKey::from_slice(&[0; constants::SCHNORR_PUBLIC_KEY_SIZE - 1]),
             Err(InvalidPublicKey)
@@ -381,6 +355,32 @@ mod tests {
         assert_eq!(XOnlyPublicKey::from_slice(&[]), Err(InvalidPublicKey));
     }
 
+    #[test]
+    #[cfg(all(feature = "rand", feature = "std"))]
+    fn test_pubkey_serialize_roundtrip() {
+        let secp = Secp256k1::new();
+        let kp = Keypair::new(&secp, &mut rand::thread_rng());
+        let (pk, _parity) = kp.x_only_public_key();
+
+        let ser = pk.serialize();
+        let pubkey2 = XOnlyPublicKey::from_slice(&ser).unwrap();
+        assert_eq!(pk, pubkey2);
+    }
+
+    #[test]
+    #[cfg(feature = "alloc")]
+    fn test_xonly_key_extraction() {
+        let secp = Secp256k1::new();
+        let sk_str = "688C77BC2D5AAFF5491CF309D4753B732135470D05B7B2CD21ADD0744FE97BEF";
+        let keypair = Keypair::from_seckey_str(&secp, sk_str).unwrap();
+        let sk = SecretKey::from_keypair(&keypair);
+        assert_eq!(SecretKey::from_str(sk_str).unwrap(), sk);
+        let pk = crate::key::PublicKey::from_keypair(&keypair);
+        assert_eq!(crate::key::PublicKey::from_secret_key(&secp, &sk), pk);
+        let (xpk, _parity) = keypair.x_only_public_key();
+        assert_eq!(XOnlyPublicKey::from(pk), xpk);
+    }
+
     #[test]
     #[cfg(feature = "std")]
     fn test_pubkey_display_output() {