Fix

packages/contracts-bedrock/contracts/echidna/FuzzAddressAliasing.sol

+pragma solidity 0.8.15;
+
+import { AddressAliasHelper } from "../vendor/AddressAliasHelper.sol";
+
+contract EchidnaFuzzAddressAliasing {
+    bool internal failedRoundtrip;
+
+    /**
+     * @notice Takes an address to be aliased with AddressAliasHelper and then unaliased
+     *         and updates the test contract's state indicating if the round trip encoding
+     *         failed.
+     */
+    function testRoundTrip(address addr) public {
+        // Alias our address
+        address aliasedAddr = AddressAliasHelper.applyL1ToL2Alias(addr);
+
+        // Unalias our address
+        address undoneAliasAddr = AddressAliasHelper.undoL1ToL2Alias(aliasedAddr);
+
+        // If our round trip aliasing did not return the original result, set our state.
+        if (addr != undoneAliasAddr) {
+            failedRoundtrip = true;
+        }
+    }
+
+    /**
+     * @custom:invariant Address aliases are always able to be undone.
+     *
+     * Asserts that an address that has been aliased with `applyL1ToL2Alias` can always
+     * be unaliased with `undoL1ToL2Alias`.
+     */
+    function echidna_round_trip_aliasing() public view returns (bool) {
+        // ASSERTION: The round trip aliasing done in testRoundTrip(...) should never fail.
+        return !failedRoundtrip;
+    }
+}
\ No newline at end of file

packages/contracts-bedrock/contracts/test/invariants/AddressAliasHelper.t.sol

-// SPDX-License-Identifier: MIT
 pragma solidity 0.8.15;
 
 import {Test} from "forge-std/Test.sol";

packages/contracts-bedrock/package.json

@@ -45,6 +45,7 @@
     "lint": "yarn lint:fix && yarn lint:check",
     "typechain": "typechain --target ethers-v5 --out-dir dist/types --glob 'artifacts/!(build-info)/**/+([a-zA-Z0-9_]).json'",
     "invariant:aliasing": "forge test --match-path ./contracts/test/invariants/AddressAliasHelper.t.sol -vvv",
+    "echidna:aliasing": "echidna-test --contract EchidnaFuzzAddressAliasing --config ./echidna.yaml .",
     "echidna:burn:gas": "echidna-test --contract EchidnaFuzzBurnGas --config ./echidna.yaml .",
     "echidna:burn:eth": "echidna-test --contract EchidnaFuzzBurnEth --config ./echidna.yaml .",
     "echidna:encoding": "echidna-test --contract EchidnaFuzzEncoding --config ./echidna.yaml .",