test: Adds suite Schnorr verify differential fuzz test

script/libs/LibOracleSuite.sol

@@ -3,6 +3,8 @@ pragma solidity ^0.8.16;
 
 import {Vm} from "forge-std/Vm.sol";
 
+import {LibSecp256k1} from "src/libs/LibSecp256k1.sol";
+
 /**
  * @title LibOracleSuite
  *
@@ -42,6 +44,38 @@ library LibOracleSuite {
         return (signature, commitment);
     }
 
+    /// @dev Verifies public key `pubKey` signs via `signature` and `commitment`
+    ///      message `message`.
+    ///
+    ///      Verified via:
+    ///      ```bash
+    ///      $ ./bin/schnorr verify \
+    ///             <message>       \
+    ///             <pubKey.x>      \
+    ///             <pubKey.y>      \
+    ///             <signature>     \
+    ///             <commitment>
+    ///      ```
+    function verify(
+        LibSecp256k1.Point memory pubKey,
+        bytes32 message,
+        bytes32 signature,
+        address commitment
+    ) internal returns (bool) {
+        string[] memory inputs = new string[](7);
+        inputs[0] = "bin/schnorr";
+        inputs[1] = "verify";
+        inputs[2] = vm.toString(message);
+        inputs[3] = vm.toString(pubKey.x);
+        inputs[4] = vm.toString(pubKey.y);
+        inputs[5] = vm.toString(signature);
+        inputs[6] = vm.toString(commitment);
+
+        uint result = abi.decode(vm.ffi(inputs), (uint));
+
+        return result == 1;
+    }
+
     /// @dev Constructs poke message for `wat` with value `val` and age `age`.
     ///
     ///      Constructed via:

test/LibSchnorrTest.sol

@@ -57,21 +57,46 @@ abstract contract LibSchnorrTest is Test {
         }
 
         // Create signature via oracle-suite.
-        uint signature;
-        address commitment;
-        (signature, commitment) = LibOracleSuite.sign(privKeys, message);
-
-        // IMPORTANT: Don't do anything if signature is invalid.
-        if (signature == 0) {
-            console2.log("Signature is zero");
-            return;
-        }
+        uint signatureSuite;
+        address commitmentSuite;
+        (signatureSuite, commitmentSuite) =
+            LibOracleSuite.sign(privKeys, message);
+
+        // Create signature via LibSchnorrExtended.
+        uint signatureLibSchnorr;
+        address commitmentLibSchnorr;
+        (signatureLibSchnorr, commitmentLibSchnorr) =
+            LibSchnorrExtended.signMessage(privKeys, message);
+
+        // Expect both signatures to be verifiable via LibSchnorr.
+        assertTrue(
+            LibSchnorr.verifySignature(
+                aggPubKey, message, bytes32(signatureSuite), commitmentSuite
+            )
+        );
+        assertTrue(
+            LibSchnorr.verifySignature(
+                aggPubKey,
+                message,
+                bytes32(signatureLibSchnorr),
+                commitmentLibSchnorr
+            )
+        );
 
-        // Expect oracle-suite's signature to be verifiable.
-        bool ok = LibSchnorr.verifySignature(
-            aggPubKey, message, bytes32(signature), commitment
+        // Expect both signatures to be verifiable via oracle-suite.
+        assertTrue(
+            LibOracleSuite.verify(
+                aggPubKey, message, bytes32(signatureSuite), commitmentSuite
+            )
+        );
+        assertTrue(
+            LibOracleSuite.verify(
+                aggPubKey,
+                message,
+                bytes32(signatureLibSchnorr),
+                commitmentLibSchnorr
+            )
         );
-        assertTrue(ok);
     }
 
     function testFuzz_verifySignature_SingleSigner(