diff --git a/packages/contracts/contracts/optimistic-ethereum/bridge/BaseMockCrossDomainMessenger.sol b/packages/contracts/contracts/optimistic-ethereum/bridge/BaseMockCrossDomainMessenger.sol
deleted file mode 100644
index 6825ce3284f1d..0000000000000
--- a/packages/contracts/contracts/optimistic-ethereum/bridge/BaseMockCrossDomainMessenger.sol
+++ /dev/null
@@ -1,102 +0,0 @@
-pragma solidity ^0.5.0;
-
-/**
- * @title BaseMockCrossDomainMessenger
- */
-contract BaseMockCrossDomainMessenger {
-    /*
-     * Contract Variables
-     */
-
-    mapping (uint256 => bytes) internal fullSentMessages;
-    uint256 public messagesToRelay;
-    uint256 public lastRelayedMessage;
-
-
-    /*
-     * Public Functions
-     */
-
-    function relayMessageToTarget()
-        public
-    {
-        require(
-            lastRelayedMessage < messagesToRelay,
-            "Already relayed all of the messages!"
-        );
-
-        bytes memory topMessage = fullSentMessages[lastRelayedMessage];
-
-        (
-            address target,
-            address sender,
-            bytes memory message,
-            uint256 messageNonce
-        ) = _decodeXDomainCalldata(topMessage);
-
-        _relayXDomainMessageToTarget(
-            target,
-            sender,
-            message,
-            messageNonce
-        );
-
-        lastRelayedMessage += 1;
-    }
-
-
-    /*
-     * Internal Functions
-     */
-
-    /**
-     * Sends a cross domain message.
-     */
-    function _sendXDomainMessage(
-        bytes memory _message
-    )
-        internal
-    {
-        fullSentMessages[messagesToRelay] = _message;
-        messagesToRelay += 1;
-
-        return;
-    }
-
-    /**
-     * Internal relay function.
-     */
-    function _relayXDomainMessageToTarget(
-        address _target,
-        address _sender,
-        bytes memory _message,
-        uint256 _messageNonce
-    )
-        internal
-    {
-        return;
-    }
-
-    /**
-     * Generates the correct cross domain calldata for a message.
-     * @param _target Target contract address.
-     * @param _sender Message sender address.
-     * @param _message Message to send to the target.
-     * @param _messageNonce Nonce for the provided message.
-     * @return ABI encoded cross domain calldata.
-     */
-    function _decodeXDomainCalldata(
-        bytes memory _calldata
-    )
-        internal
-        pure
-        returns (
-            address _target,
-            address _sender,
-            bytes memory _message,
-            uint256 _messageNonce
-        )
-    {
-        return abi.decode(_calldata, (address, address, bytes, uint256));
-    }
-}
diff --git a/packages/contracts/contracts/optimistic-ethereum/bridge/MockL1CrossDomainMessenger.sol b/packages/contracts/contracts/optimistic-ethereum/bridge/MockL1CrossDomainMessenger.sol
deleted file mode 100644
index 5e94cc9c44ab1..0000000000000
--- a/packages/contracts/contracts/optimistic-ethereum/bridge/MockL1CrossDomainMessenger.sol
+++ /dev/null
@@ -1,53 +0,0 @@
-pragma solidity ^0.5.0;
-pragma experimental ABIEncoderV2;
-
-/* Interface Imports */
-import { IL2CrossDomainMessenger } from "./L2CrossDomainMessenger.interface.sol";
-
-/* Contract Imports */
-import { BaseMockCrossDomainMessenger } from "./BaseMockCrossDomainMessenger.sol";
-import { L1CrossDomainMessenger } from "./L1CrossDomainMessenger.sol";
-
-/**
- * @title MockL1CrossDomainMessenger
- */
-contract MockL1CrossDomainMessenger is BaseMockCrossDomainMessenger, L1CrossDomainMessenger {
-    /*
-     * Internal Functions
-     */
-
-    /**
-     * Verifies that the given message is valid.
-     * .inheritdoc L1CrossDomainMessenger
-     */
-    function _verifyXDomainMessage(
-        bytes memory _xDomainCalldata,
-        L2MessageInclusionProof memory _proof
-    )
-        internal
-        returns (
-            bool
-        )
-    {
-        return true;
-    }
-
-    /**
-     * Internal relay function.
-     */
-    function _relayXDomainMessageToTarget(
-        address _target,
-        address _sender,
-        bytes memory _message,
-        uint256 _messageNonce
-    )
-        internal
-    {
-        IL2CrossDomainMessenger(targetMessengerAddress).relayMessage(
-            _target,
-            _sender,
-            _message,
-            _messageNonce
-        );
-    }
-}
diff --git a/packages/contracts/contracts/optimistic-ethereum/bridge/MockL2CrossDomainMessenger.sol b/packages/contracts/contracts/optimistic-ethereum/bridge/MockL2CrossDomainMessenger.sol
deleted file mode 100644
index f519a3f76fd1a..0000000000000
--- a/packages/contracts/contracts/optimistic-ethereum/bridge/MockL2CrossDomainMessenger.sol
+++ /dev/null
@@ -1,68 +0,0 @@
-pragma solidity ^0.5.0;
-
-/* Interface Imports */
-import { IL1CrossDomainMessenger } from "./L1CrossDomainMessenger.interface.sol";
-
-/* Library Imports */
-import { DataTypes } from "../utils/libraries/DataTypes.sol";
-
-/* Contract Imports */
-import { BaseMockCrossDomainMessenger } from "./BaseMockCrossDomainMessenger.sol";
-import { L2CrossDomainMessenger } from "./L2CrossDomainMessenger.sol";
-
-/**
- * @title MockL2CrossDomainMessenger
- */
-contract MockL2CrossDomainMessenger is BaseMockCrossDomainMessenger, L2CrossDomainMessenger {
-    /*
-     * Internal Functions
-     */
-
-    /**
-     * Verifies that a received cross domain message is valid.
-     * .inheritdoc L2CrossDomainMessenger
-     */
-    function _verifyXDomainMessage()
-        internal
-        returns (
-            bool
-        )
-    {
-        return true;
-    }
-
-    /**
-     * Internal relay function.
-     */
-    function _relayXDomainMessageToTarget(
-        address _target,
-        address _sender,
-        bytes memory _message,
-        uint256 _messageNonce
-    )
-        internal
-    {
-        IL1CrossDomainMessenger(targetMessengerAddress).relayMessage(
-            _target,
-            _sender,
-            _message,
-            _messageNonce,
-            IL1CrossDomainMessenger.L2MessageInclusionProof({
-                stateRoot: bytes32(''),
-                stateRootIndex: 0,
-                stateRootProof: DataTypes.StateElementInclusionProof({
-                    batchIndex: 0,
-                    batchHeader: DataTypes.StateChainBatchHeader({
-                        elementsMerkleRoot: bytes32(''),
-                        numElementsInBatch: 0,
-                        cumulativePrevElements: 0
-                    }),
-                    indexInBatch: 0,
-                    siblings: new bytes32[](1)
-                }),
-                stateTrieWitness: bytes(''),
-                storageTrieWitness: bytes('')
-            })
-        );
-    }
-}
diff --git a/packages/contracts/contracts/optimistic-ethereum/bridge/mocks/MockCrossDomainMessenger.sol b/packages/contracts/contracts/optimistic-ethereum/bridge/mocks/MockCrossDomainMessenger.sol
new file mode 100644
index 0000000000000..3ad349a932c14
--- /dev/null
+++ b/packages/contracts/contracts/optimistic-ethereum/bridge/mocks/MockCrossDomainMessenger.sol
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.5.0;
+pragma experimental ABIEncoderV2;
+
+/* Contract Imports */
+import { BaseCrossDomainMessenger } from "../BaseCrossDomainMessenger.sol";
+
+/**
+ * @title MockCrossDomainMessenger
+ */
+contract MockCrossDomainMessenger is BaseCrossDomainMessenger {
+
+    /***********
+     * Structs *
+     ***********/
+
+    struct ReceivedMessage {
+        uint256 timestamp;
+        address target;
+        address sender;
+        bytes message;
+        uint256 messageNonce;
+        uint256 gasLimit;
+    }
+
+
+    /**********************
+     * Contract Variables *
+     **********************/
+
+    ReceivedMessage[] internal fullReceivedMessages;
+    uint256 internal lastRelayedMessage;
+    uint256 internal delay;
+
+
+    /***************
+     * Constructor *
+     ***************/
+
+    /**
+     * @param _delay Time in seconds before a message can be relayed.
+     */
+    constructor(
+        uint256 _delay
+    )
+        public
+    {
+        delay = _delay;
+    }
+
+
+    /********************
+     * Public Functions *
+     ********************/
+
+    /**
+     * Sends a message to another mock xdomain messenger.
+     * @param _target Target for the message.
+     * @param _message Message to send.
+     * @param _gasLimit Amount of gas to send with the call.
+     */
+    function sendMessage(
+        address _target,
+        bytes memory _message,
+        uint32 _gasLimit
+    )
+        public
+    {
+        MockCrossDomainMessenger targetMessenger = MockCrossDomainMessenger(
+            targetMessengerAddress
+        );
+
+        // Just send it over!
+        targetMessenger.receiveMessage(ReceivedMessage({
+            timestamp: block.timestamp,
+            target: _target,
+            sender: msg.sender,
+            message: _message,
+            messageNonce: messageNonce,
+            gasLimit: _gasLimit
+        }));
+
+        messageNonce += 1;
+    }
+
+    /**
+     * Receives a message to be sent later.
+     * @param _message Message to send later.
+     */
+    function receiveMessage(
+        ReceivedMessage memory _message
+    )
+        public
+    {
+        fullReceivedMessages.push(_message);
+    }
+
+    /**
+     * Checks whether we have messages to relay.
+     * @param _exists Whether or not we have more messages to relay.
+     */
+    function hasNextMessage()
+        public
+        view
+        returns (
+            bool _exists
+        )
+    {
+        if (fullReceivedMessages.length <= lastRelayedMessage) {
+            return false;
+        }
+
+        ReceivedMessage memory nextMessage = fullReceivedMessages[lastRelayedMessage];
+        return nextMessage.timestamp + delay < block.timestamp;
+    }
+
+    /**
+     * Relays the last received message not yet relayed.
+     */
+    function relayNextMessage()
+        public
+    {
+        if (hasNextMessage() == false) {
+            return;
+        }
+
+        ReceivedMessage memory nextMessage = fullReceivedMessages[lastRelayedMessage];
+        xDomainMessageSender = nextMessage.sender;
+        nextMessage.target.call.gas(nextMessage.gasLimit)(nextMessage.message);
+        lastRelayedMessage += 1;
+    }
+}
diff --git a/packages/contracts/package.json b/packages/contracts/package.json
index bfd00a7f2b1e5..8a1fb123e2965 100644
--- a/packages/contracts/package.json
+++ b/packages/contracts/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@eth-optimism/rollup-contracts",
   "private": true,
-  "version": "0.0.1-alpha.29",
+  "version": "0.0.1-alpha.32",
   "main": "build/index.js",
   "files": [
     "build/**/*.js",
@@ -41,11 +41,10 @@
   },
   "dependencies": {
     "@ethersproject/keccak256": "5.0.3",
-    "@eth-optimism/core-db": "^0.0.1-alpha.28",
-    "@eth-optimism/core-utils": "^0.0.1-alpha.28",
-    "@eth-optimism/solc": "^0.5.16-alpha.0",
-    "@eth-optimism/solc-transpiler": "^0.0.1-alpha.27",
-    "@nomiclabs/buidler": "^1.3.8",
+    "@eth-optimism/core-db": "^0.0.1-alpha.30",
+    "@eth-optimism/core-utils": "^0.0.1-alpha.30",
+    "@eth-optimism/solc": "^0.5.16-alpha.2",
+    "@nomiclabs/buidler": "1.3.8",
     "@nomiclabs/buidler-ethers": "^2.0.0",
     "@nomiclabs/buidler-solpp": "^1.3.3",
     "@nomiclabs/buidler-waffle": "^2.0.0",
diff --git a/packages/core-db/package.json b/packages/core-db/package.json
index 45f7f7c51df5e..c01e612e7aaf9 100644
--- a/packages/core-db/package.json
+++ b/packages/core-db/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@eth-optimism/core-db",
-  "version": "0.0.1-alpha.28",
+  "version": "0.0.1-alpha.30",
   "description": "Optimism DB Utils",
   "main": "build/index.js",
   "files": [
@@ -30,7 +30,7 @@
     "url": "https://github.com/ethereum-optimism/optimism-monorepo.git"
   },
   "dependencies": {
-    "@eth-optimism/core-utils": "^0.0.1-alpha.28",
+    "@eth-optimism/core-utils": "^0.0.1-alpha.30",
     "abstract-leveldown": "^6.2.2",
     "async-lock": "^1.2.2",
     "chai": "^4.2.0",
diff --git a/packages/core-utils/package.json b/packages/core-utils/package.json
index 4a5f2985c642c..3dc3b7f1baf8f 100644
--- a/packages/core-utils/package.json
+++ b/packages/core-utils/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@eth-optimism/core-utils",
-  "version": "0.0.1-alpha.28",
+  "version": "0.0.1-alpha.30",
   "description": "Optimism Core Utils",
   "main": "build/index.js",
   "files": [
@@ -39,7 +39,7 @@
     "debug": "^4.1.1",
     "dotenv": "^8.2.0",
     "ethereumjs-util": "^6.2.0",
-    "ethers": "^4.0.37",
+    "ethers-v4": "npm:ethers@4",
     "express": "^4.17.1",
     "memdown": "^4.0.0",
     "ts-md5": "^1.2.4",
diff --git a/packages/core-utils/src/app/contract-deployment.ts b/packages/core-utils/src/app/contract-deployment.ts
index e49611a29d33f..5af5b72ce4349 100644
--- a/packages/core-utils/src/app/contract-deployment.ts
+++ b/packages/core-utils/src/app/contract-deployment.ts
@@ -2,9 +2,9 @@
 
 /* External Imports */
 import { config } from 'dotenv'
-import { Contract, ContractFactory, ethers, Wallet } from 'ethers'
-import { stripZeros, hexlify, RLP, getAddress } from 'ethers/utils'
-import { Provider } from 'ethers/providers'
+import { Contract, ContractFactory, ethers, Wallet } from 'ethers-v4'
+import { stripZeros, hexlify, RLP, getAddress } from 'ethers-v4/utils'
+import { Provider } from 'ethers-v4/providers'
 
 /* Internal Imports */
 import { ContractDeploymentFunction } from '../types'
diff --git a/packages/core-utils/src/app/crypto.ts b/packages/core-utils/src/app/crypto.ts
index 2121c56c5fc0c..f916c49137ef3 100644
--- a/packages/core-utils/src/app/crypto.ts
+++ b/packages/core-utils/src/app/crypto.ts
@@ -1,12 +1,12 @@
 /* External Imports */
 import { Md5 } from 'ts-md5'
-import { ethers } from 'ethers'
-import { TransactionRequest } from 'ethers/providers/abstract-provider'
+import { ethers } from 'ethers-v4'
+import { TransactionRequest } from 'ethers-v4/providers/abstract-provider'
 import {
   joinSignature,
   resolveProperties,
   serializeTransaction,
-} from 'ethers/utils'
+} from 'ethers-v4/utils'
 
 /* Internal Imports */
 import { HashAlgorithm, HashFunction } from '../types'
diff --git a/packages/core-utils/src/app/ethereum.ts b/packages/core-utils/src/app/ethereum.ts
index dd6122c76e5d0..2e398658ca1ef 100644
--- a/packages/core-utils/src/app/ethereum.ts
+++ b/packages/core-utils/src/app/ethereum.ts
@@ -1,9 +1,9 @@
-import { Contract, Wallet } from 'ethers'
+import { Contract, Wallet } from 'ethers-v4'
 import {
   Provider,
   TransactionRequest,
   TransactionResponse,
-} from 'ethers/providers'
+} from 'ethers-v4/providers'
 import { getLogger } from './log'
 import { Logger } from '../types'
 
diff --git a/packages/core-utils/src/app/index.ts b/packages/core-utils/src/app/index.ts
index 9f2c66d3ee27b..eb3c9d9aff0cb 100644
--- a/packages/core-utils/src/app/index.ts
+++ b/packages/core-utils/src/app/index.ts
@@ -1,5 +1,5 @@
 /* External Imports */
-import { ethers } from 'ethers'
+import { ethers } from 'ethers-v4'
 
 /* Abi */
 export const abi = new ethers.utils.AbiCoder()
diff --git a/packages/core-utils/src/app/misc.ts b/packages/core-utils/src/app/misc.ts
index fd80c275d5509..36b1f416be34e 100644
--- a/packages/core-utils/src/app/misc.ts
+++ b/packages/core-utils/src/app/misc.ts
@@ -3,7 +3,7 @@ import * as domain from 'domain'
 
 /* Internal Imports */
 import { BigNumber } from './number'
-import { RLP, hexlify } from 'ethers/utils'
+import { RLP, hexlify } from 'ethers-v4/utils'
 
 export const NULL_ADDRESS = '0x0000000000000000000000000000000000000000'
 const hexRegex = /^(0x)?[0-9a-fA-F]*$/
diff --git a/packages/core-utils/src/app/signatures.ts b/packages/core-utils/src/app/signatures.ts
index d7aed0ce3a956..5aa0550a42286 100644
--- a/packages/core-utils/src/app/signatures.ts
+++ b/packages/core-utils/src/app/signatures.ts
@@ -1,5 +1,5 @@
 /* Internal Imports */
-import { ethers } from 'ethers'
+import { ethers } from 'ethers-v4'
 import { SignatureProvider, SignatureVerifier } from '../types'
 import { hexStrToBuf } from './misc'
 
diff --git a/packages/core-utils/src/types/contract-deployment.ts b/packages/core-utils/src/types/contract-deployment.ts
index 083bb0527b40d..ef2765ac00b18 100644
--- a/packages/core-utils/src/types/contract-deployment.ts
+++ b/packages/core-utils/src/types/contract-deployment.ts
@@ -1,4 +1,4 @@
-import { Wallet } from 'ethers'
+import { Wallet } from 'ethers-v4'
 
 /**
  * Deploys a contract and returns its deployed address.
diff --git a/packages/core-utils/src/types/type-guards.ts b/packages/core-utils/src/types/type-guards.ts
index 9eea8a5463458..3263764b5ec65 100644
--- a/packages/core-utils/src/types/type-guards.ts
+++ b/packages/core-utils/src/types/type-guards.ts
@@ -9,7 +9,7 @@ import { ZERO, add0x } from '../app'
 import { Address } from 'cluster'
 
 /* External Imports */
-import { ethers } from 'ethers'
+import { ethers } from 'ethers-v4'
 
 /**
  * Checks if a JSON-RPC response is an error response.
diff --git a/packages/core-utils/test/app/contract-deployment.spec.ts b/packages/core-utils/test/app/contract-deployment.spec.ts
index e013afb6f05bb..f8b1a4fd4ec89 100644
--- a/packages/core-utils/test/app/contract-deployment.spec.ts
+++ b/packages/core-utils/test/app/contract-deployment.spec.ts
@@ -2,8 +2,8 @@ import { should } from '../setup'
 
 /* External Imports */
 import { createMockProvider, getWallets } from 'ethereum-waffle'
-import { ContractFactory, Wallet } from 'ethers'
-import { Provider } from 'ethers/providers'
+import { ContractFactory, Wallet } from 'ethers-v4'
+import { Provider } from 'ethers-v4/providers'
 
 /* Internal Imports */
 import { getDeployedContractAddress } from '../../src/app'
diff --git a/packages/ovm-toolchain/package.json b/packages/ovm-toolchain/package.json
index 2be67ff13483a..93d393bf986f7 100644
--- a/packages/ovm-toolchain/package.json
+++ b/packages/ovm-toolchain/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@eth-optimism/ovm-toolchain",
-  "version": "0.0.1-alpha.1",
+  "version": "0.0.1-alpha.5",
   "description": "Wrappers for Ethereum dev tools",
   "private": true,
   "main": "build/index.js",
@@ -49,7 +49,7 @@
     "access": "public"
   },
   "devDependencies": {
-    "@eth-optimism/solc": "^0.5.16-alpha.0",
+    "@eth-optimism/solc": "^0.5.16-alpha.2",
     "@nomiclabs/buidler": "^1.4.4",
     "@nomiclabs/buidler-ethers": "^2.0.0",
     "@nomiclabs/buidler-waffle": "^2.0.0",
@@ -68,9 +68,8 @@
     "web3": "^1.2.11"
   },
   "dependencies": {
-    "@eth-optimism/core-utils": "^0.0.1-alpha.27",
-    "@eth-optimism/rollup-contracts": "^0.0.1-alpha.29",
-    "@eth-optimism/solc-transpiler": "^0.0.1-alpha.28",
+    "@eth-optimism/core-utils": "^0.0.1-alpha.30",
+    "@eth-optimism/rollup-contracts": "^0.0.1-alpha.32",
     "@nomiclabs/buidler": "^1.4.4",
     "bn.js": "^5.1.3",
     "child_process": "^1.0.2",
diff --git a/packages/ovm-toolchain/src/waffle/waffle-v2.ts b/packages/ovm-toolchain/src/waffle/waffle-v2.ts
index 3e6063b54028d..2a6dc13c1e688 100644
--- a/packages/ovm-toolchain/src/waffle/waffle-v2.ts
+++ b/packages/ovm-toolchain/src/waffle/waffle-v2.ts
@@ -5,15 +5,25 @@ import Ganache from 'ganache-core'
 
 /* Internal Imports */
 import { ganache } from '../ganache'
-import { initCrossDomainMessengersVX } from './waffle-vx'
+import {
+  initCrossDomainMessengersVX,
+  waitForCrossDomainMessages,
+} from './waffle-vx'
 
-export const initCrossDomainMessengers = async (
-  provider: any
+const initCrossDomainMessengers = async (
+  l1ToL2MessageDelay: number,
+  l2ToL1MessageDelay: number,
+  signer: any
 ): Promise<{
   l1CrossDomainMessenger: Contract
   l2CrossDomainMessenger: Contract
 }> => {
-  return initCrossDomainMessengersVX(ethers, provider)
+  return initCrossDomainMessengersVX(
+    l1ToL2MessageDelay,
+    l2ToL1MessageDelay,
+    ethers,
+    signer
+  )
 }
 
 /**
@@ -72,4 +82,6 @@ export class MockProvider extends providers.Web3Provider {
 
 export const waffleV2 = {
   MockProvider,
+  initCrossDomainMessengers,
+  waitForCrossDomainMessages,
 }
diff --git a/packages/ovm-toolchain/src/waffle/waffle-v3.ts b/packages/ovm-toolchain/src/waffle/waffle-v3.ts
index b2681038d1182..8ae5b38b8e5fe 100644
--- a/packages/ovm-toolchain/src/waffle/waffle-v3.ts
+++ b/packages/ovm-toolchain/src/waffle/waffle-v3.ts
@@ -5,17 +5,25 @@ import Ganache from 'ganache-core'
 
 /* Internal Imports */
 import { ganache } from '../ganache'
-import { initCrossDomainMessengersVX } from './waffle-vx'
-
-export { waitForCrossDomainMessages } from './waffle-vx'
+import {
+  initCrossDomainMessengersVX,
+  waitForCrossDomainMessages,
+} from './waffle-vx'
 
 export const initCrossDomainMessengers = async (
-  provider: any
+  l1ToL2MessageDelay: number,
+  l2ToL1MessageDelay: number,
+  signer: any
 ): Promise<{
   l1CrossDomainMessenger: Contract
   l2CrossDomainMessenger: Contract
 }> => {
-  return initCrossDomainMessengersVX(ethers, provider)
+  return initCrossDomainMessengersVX(
+    l1ToL2MessageDelay,
+    l2ToL1MessageDelay,
+    ethers,
+    signer
+  )
 }
 
 interface MockProviderOptions {
@@ -48,4 +56,6 @@ export class MockProvider extends providers.Web3Provider {
 
 export const waffleV3 = {
   MockProvider,
+  initCrossDomainMessengers,
+  waitForCrossDomainMessages,
 }
diff --git a/packages/ovm-toolchain/src/waffle/waffle-vx.ts b/packages/ovm-toolchain/src/waffle/waffle-vx.ts
index 48a4388fddc8d..985406add71e9 100644
--- a/packages/ovm-toolchain/src/waffle/waffle-vx.ts
+++ b/packages/ovm-toolchain/src/waffle/waffle-vx.ts
@@ -11,6 +11,7 @@ import { getContractDefinition } from '@eth-optimism/rollup-contracts'
  */
 const getContractFromDefinition = (
   ethers: any,
+  signer: any,
   name: string,
   args: any[] = []
 ): any => {
@@ -18,7 +19,8 @@ const getContractFromDefinition = (
 
   const contractFactory = new ethers.ContractFactory(
     contractDefinition.abi,
-    contractDefinition.bytecode
+    contractDefinition.bytecode,
+    signer
   )
 
   return contractFactory.deploy(...args)
@@ -31,20 +33,26 @@ const getContractFromDefinition = (
  * @returns Both cross domain messenger objects.
  */
 export const initCrossDomainMessengersVX = async (
+  l1ToL2MessageDelay: number,
+  l2ToL1MessageDelay: number,
   ethers: any,
-  provider: any
+  signer: any
 ): Promise<{
   l1CrossDomainMessenger: any
   l2CrossDomainMessenger: any
 }> => {
-  const l1CrossDomainMessenger = getContractFromDefinition(
+  const l1CrossDomainMessenger = await getContractFromDefinition(
     ethers,
-    'MockL1CrossDomainMessenger'
+    signer,
+    'MockCrossDomainMessenger',
+    [l2ToL1MessageDelay]
   )
 
-  const l2CrossDomainMessenger = getContractFromDefinition(
+  const l2CrossDomainMessenger = await getContractFromDefinition(
     ethers,
-    'MockL2CrossDomainMessenger'
+    signer,
+    'MockCrossDomainMessenger',
+    [l1ToL2MessageDelay]
   )
 
   await l1CrossDomainMessenger.setTargetMessengerAddress(
@@ -54,8 +62,8 @@ export const initCrossDomainMessengersVX = async (
     l1CrossDomainMessenger.address
   )
 
-  provider.__l1CrossDomainMessenger = l1CrossDomainMessenger
-  provider.__l2CrossDomainMessenger = l2CrossDomainMessenger
+  signer.provider.__l1CrossDomainMessenger = l1CrossDomainMessenger
+  signer.provider.__l2CrossDomainMessenger = l2CrossDomainMessenger
 
   return {
     l1CrossDomainMessenger,
@@ -68,10 +76,10 @@ export const initCrossDomainMessengersVX = async (
  * @param provider Ethers provider with attached messengers.
  */
 export const waitForCrossDomainMessages = async (
-  provider: any
+  signer: any
 ): Promise<void> => {
-  const l1CrossDomainMessenger = provider.__l1CrossDomainMessenger
-  const l2CrossDomainMessenger = provider.__l2CrossDomainMessenger
+  const l1CrossDomainMessenger = signer.provider.__l1CrossDomainMessenger
+  const l2CrossDomainMessenger = signer.provider.__l2CrossDomainMessenger
 
   if (!l1CrossDomainMessenger || !l2CrossDomainMessenger) {
     throw new Error(
@@ -79,11 +87,11 @@ export const waitForCrossDomainMessages = async (
     )
   }
 
-  while ((await l1CrossDomainMessenger.messagesToRelay()) > 0) {
-    await l1CrossDomainMessenger.relayMessageToTarget()
+  while (await l1CrossDomainMessenger.hasNextMessage()) {
+    await l1CrossDomainMessenger.relayNextMessage()
   }
 
-  while ((await l2CrossDomainMessenger.messagesToRelay()) > 0) {
-    await l2CrossDomainMessenger.relayMessageToTarget()
+  while (await l2CrossDomainMessenger.hasNextMessage()) {
+    await l2CrossDomainMessenger.relayNextMessage()
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 31a3254169365..d73130ded683f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -60,6 +60,20 @@
     ts-md5 "^1.2.4"
     uuid "^3.3.3"
 
+"@eth-optimism/ovm-toolchain@0.0.1-alpha.1":
+  version "0.0.1-alpha.1"
+  resolved "https://registry.yarnpkg.com/@eth-optimism/ovm-toolchain/-/ovm-toolchain-0.0.1-alpha.1.tgz#69ebb93723ae0bf1fd5210366afa8456c90e86ed"
+  integrity sha512-nqGWNSvIYvbHXB71ulkiZIALkcZYq43G6E5WMfTn/g/rLM7GALZuTZ6AjoFguPkYmsd9wLa9dPCWx7pKc7D/dg==
+  dependencies:
+    "@eth-optimism/core-utils" "^0.0.1-alpha.27"
+    "@eth-optimism/solc-transpiler" "^0.0.1-alpha.28"
+    "@nomiclabs/buidler" "^1.4.4"
+    ethereum-waffle-v2 "npm:ethereum-waffle@2"
+    ethereum-waffle-v3 "npm:ethereum-waffle@3"
+    ethereumjs-ovm "git+https://github.com/ethereum-optimism/ethereumjs-vm"
+    ethers-v4 "npm:ethers@4"
+    ethers-v5 "npm:ethers@5.0.7"
+
 "@eth-optimism/rollup-core@^0.0.1-alpha.28":
   version "0.0.1-alpha.28"
   resolved "https://registry.yarnpkg.com/@eth-optimism/rollup-core/-/rollup-core-0.0.1-alpha.28.tgz#845de41ed266e0f1fd738776cb68bfe1fa391104"
@@ -86,7 +100,7 @@
     ethereumjs-vm "^4.1.3"
     ethers "^4.0.42"
 
-"@eth-optimism/solc-transpiler@^0.0.1-alpha.27", "@eth-optimism/solc-transpiler@^0.0.1-alpha.28":
+"@eth-optimism/solc-transpiler@^0.0.1-alpha.28":
   version "0.0.1-alpha.28"
   resolved "https://registry.yarnpkg.com/@eth-optimism/solc-transpiler/-/solc-transpiler-0.0.1-alpha.28.tgz#327743c7c0271dac13243fb4de22e1f0ee81b31c"
   integrity sha512-UyQK6AseKfG1h1kRW+Atu9z0z0Ym3MW+ncoiRK+7TUbKyrDcKuBlLst+FXuo6fChHkw25oDfHpb3t/oTLDLlCg==
@@ -112,6 +126,21 @@
     semver "^5.5.0"
     tmp "0.0.33"
 
+"@eth-optimism/solc@^0.5.16-alpha.2":
+  version "0.5.16-alpha.2"
+  resolved "https://registry.yarnpkg.com/@eth-optimism/solc/-/solc-0.5.16-alpha.2.tgz#24e92d93682b2895fc4de70a2ab28b80e78000cb"
+  integrity sha512-c8Ynl6teu5z7kKOweGB8V629liKTIC/udnuwpdImQgBGyp6BTMXwgBPKQkHagCC5eTAEr9jGF+ENvt6ppxElGA==
+  dependencies:
+    command-exists "^1.2.8"
+    commander "3.0.2"
+    follow-redirects "^1.12.1"
+    fs-extra "^0.30.0"
+    js-sha3 "0.8.0"
+    memorystream "^0.3.1"
+    require-from-string "^2.0.0"
+    semver "^5.5.0"
+    tmp "0.0.33"
+
 "@ethereum-waffle/chai@^2.5.1":
   version "2.5.1"
   resolved "https://registry.yarnpkg.com/@ethereum-waffle/chai/-/chai-2.5.1.tgz#8bdc055952fc80ff78132571396a2771a36d97ae"
@@ -1361,7 +1390,53 @@
     "@types/sinon-chai" "^3.2.3"
     "@types/web3" "1.0.19"
 
-"@nomiclabs/buidler@^1.3.8", "@nomiclabs/buidler@^1.4.4":
+"@nomiclabs/buidler@1.3.8":
+  version "1.3.8"
+  resolved "https://registry.yarnpkg.com/@nomiclabs/buidler/-/buidler-1.3.8.tgz#55013ed8513afbd0d06ff9d00f6fa8b5e6173982"
+  integrity sha512-SmSsNteks20Vl4WBELRV8Vnokh1CxbPHFF5aBqhe/4tR2QVR51dNy8dwDkmj153UyAW+f6ZtxF9QT+TxNomZBg==
+  dependencies:
+    "@nomiclabs/ethereumjs-vm" "^4.1.1"
+    "@solidity-parser/parser" "^0.5.2"
+    "@types/bn.js" "^4.11.5"
+    "@types/lru-cache" "^5.1.0"
+    abort-controller "^3.0.0"
+    ansi-escapes "^4.3.0"
+    chalk "^2.4.2"
+    ci-info "^2.0.0"
+    debug "^4.1.1"
+    deepmerge "^2.1.0"
+    download "^7.1.0"
+    enquirer "^2.3.0"
+    eth-sig-util "^2.5.2"
+    ethereum-cryptography "^0.1.2"
+    ethereumjs-abi "^0.6.8"
+    ethereumjs-account "^3.0.0"
+    ethereumjs-block "^2.2.0"
+    ethereumjs-common "^1.3.2"
+    ethereumjs-tx "^2.1.1"
+    ethereumjs-util "^6.1.0"
+    find-up "^2.1.0"
+    fp-ts "1.19.3"
+    fs-extra "^7.0.1"
+    glob "^7.1.3"
+    io-ts "1.10.4"
+    is-installed-globally "^0.2.0"
+    lodash "^4.17.11"
+    merkle-patricia-tree "^3.0.0"
+    mocha "^7.1.2"
+    node-fetch "^2.6.0"
+    qs "^6.7.0"
+    raw-body "^2.4.1"
+    semver "^6.3.0"
+    slash "^3.0.0"
+    solc "0.6.8"
+    source-map-support "^0.5.13"
+    ts-essentials "^2.0.7"
+    tsort "0.0.1"
+    uuid "^3.3.2"
+    ws "^7.2.1"
+
+"@nomiclabs/buidler@^1.4.4":
   version "1.4.5"
   resolved "https://registry.yarnpkg.com/@nomiclabs/buidler/-/buidler-1.4.5.tgz#9e332918bf0c19416494e3c4580fd3ca350ed70b"
   integrity sha512-jaaVvG7OsrObhEBnLtQ/8L3J92+Jgioaw2+296dDO4Uc+MO/kprORbnpbE/WKvPL1geKQ4uj6VdCpM7qNCwL3g==