feat: implement mock attestation

src/AvailAttestation.sol

@@ -25,12 +25,13 @@ abstract contract AvailAttestation is Initializable {
     error InvalidAttestationProof();
     event Attested(bytes32 indexed leaf, uint32 indexed blockNumber, uint128 indexed leafIndex);
 
-    function initialize(IAvailBridge _bridge) external initializer {
+    // slither-disable-next-line naming-convention,dead-code
+    function __AvailAttestation_init(IAvailBridge _bridge) internal virtual onlyInitializing {
         bridge = _bridge;
         vectorx = bridge.vectorx();
     }
 
-    function _attest(IAvailBridge.MerkleProofInput calldata input) external {
+    function _attest(IAvailBridge.MerkleProofInput calldata input) internal virtual {
         if (!bridge.verifyBlobLeaf(input)) revert InvalidAttestationProof();
         attestations[input.leaf] = AttestationData(
             vectorx.rangeStartBlocks(input.rangeHash) + uint32(input.dataRootIndex),

src/mocks/AvailAttestationMock.sol

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.25;
+
+import {Initializable} from "lib/openzeppelin-contracts-upgradeable/contracts/proxy/utils/Initializable.sol";
+import {IAvailBridge} from "src/interfaces/IAvailBridge.sol";
+import {AvailAttestation} from "src/AvailAttestation.sol";
+
+/**
+ * @author  @QEDK (Avail)
+ * @title   AvailAttestationMock
+ * @notice  An mock data attestation implementation for validiums, optimiums and generic rollup stacks
+ * @custom:security security@availproject.org
+ */
+contract AvailAttestationMock is Initializable, AvailAttestation {
+    function initialize(IAvailBridge _bridge) external initializer {
+        __AvailAttestation_init(_bridge);
+    }
+
+    // this function signature should differ based on rollup contract's expected function signature
+    function attest(IAvailBridge.MerkleProofInput calldata input) external {
+        _attest(input);
+    }
+}