feat: smock (#8)

* chore(core-utils): cleanup dir config files

* fix: use proper tsconfig files

* feat: copy over smock

.github/workflows/ci.yml

@@ -38,6 +38,9 @@ jobs:
       - name: Install Dependencies
         run: yarn install
 
+      - name: Build
+        run: yarn build
+
       - name: Lint
         run: yarn lint
 

.gitignore

-node_modules/
+node_modules
+dist
+results
+.nyc_output
+*.tsbuildinfo

README.md

@@ -6,10 +6,12 @@
 git clone git@github.com:ethereum-optimism/optimism.git
 cd optimism
 yarn
-yarn lint
+yarn build # this is needed to generate the dist files locally
 yarn test
 ```
 
+If you get dependency errors: `git clean -fx && yarn clean && rm -rf node_modules/@eth-optimism/* && yarn install --force`
+
 ## Taming the Monorepo
 
 1. You solely use yarn workspaces for the Mono-Repo workflow.

package.json

 {
   "name": "optimism",
   "version": "1.0.0",
-  "main": "index.js",
   "license": "MIT",
   "workspaces": [
     "packages/*"
@@ -11,7 +10,10 @@
     "lerna": "^4.0.0"
   },
   "scripts": {
+      "clean": "yarn workspaces run clean",
+      "build": "yarn workspaces run build",
       "test": "yarn workspaces run test",
-      "lint": "yarn workspaces run lint"
+      "lint": "yarn workspaces run lint",
+      "lint:fix": "yarn workspaces run lint:fix"
   }
 }

packages/core-utils/package.json

 {
   "name": "@eth-optimism/core-utils",
   "version": "0.1.10",
-  "main": "build/src/index.js",
+  "main": "dist/index",
   "files": [
-    "build/src/**/*"
+    "dist/index"
   ],
   "types": "build/src/index.d.ts",
   "repository": "git@github.com:ethereum-optimism/core-utils.git",
@@ -11,8 +11,8 @@
   "license": "MIT",
   "scripts": {
     "all": "yarn clean && yarn build && yarn test && yarn lint:fix && yarn lint",
-    "build": "tsc -p .",
-    "clean": "rimraf build/",
+    "build": "tsc -p tsconfig.build.json",
+    "clean": "rimraf dist/",
     "lint": "tslint --format stylish --project .",
     "lint:fix": "prettier --config prettier-config.json --write '{src,test}/**/*.ts'",
     "test": "ts-mocha test/**/*.spec.ts"
@@ -31,8 +31,6 @@
   },
   "dependencies": {
     "@ethersproject/abstract-provider": "^5.0.9",
-    "colors": "^1.4.0",
-    "debug": "^4.3.1",
     "ethers": "^5.0.31",
     "pino": "^6.11.1"
   }

packages/core-utils/prettier-config.json

-{
-    "$schema": "http://json.schemastore.org/prettierrc",
-    "trailingComma": "es5",
-    "tabWidth": 2,
-    "semi": false,
-    "singleQuote": true,
-    "arrowParens": "always"
-}

packages/core-utils/prettier-config.json

+../../prettier-config.json
\ No newline at end of file

packages/core-utils/tsconfig.build.json

+{
+  "extends": "../../tsconfig.build.json",
+
+  "compilerOptions": {
+    "rootDir": "./src",
+    "outDir": "./dist"
+  },
+
+  "include": [
+    "src/**/*"
+  ]
+}

packages/core-utils/tsconfig.json

 {
-    "extends" : "../../tsconfig.base.json"
+  "extends": "../../tsconfig.json"
 }

packages/smock/.github/CODEOWNERS

+*       @smartcontracts

packages/smock/.github/workflows/lint-build-test.yml

+name: smock - lint, build, test
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build-test-lint:
+    name: Run job on ${{matrix.node}}
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node: [ '10', '12', '14' ]
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup node ${{ matrix.node }}
+        uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node }}
+
+      # START DEPENDENCY CACHING
+      - name: Cache root deps
+        uses: actions/cache@v1
+        id: cache_base
+        with:
+          path: node_modules
+          key: ${{ runner.os }}-${{ matrix.node }}-${{ hashFiles('package.json') }}
+
+      # END DEPENDENCY CACHING
+
+      - name: Install Dependencies
+        run: yarn install
+
+      - name: Lint
+        run: yarn lint
+
+      - name: Build
+        run: |
+          yarn clean
+          yarn build
+
+      - name: Test
+        run: yarn test

packages/smock/.github/workflows/version-to-release.yml

+name: Auto tag-release-publish
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  tag:
+    name: Create tag for new version
+    runs-on: ubuntu-latest
+    outputs:
+      tag_name: ${{ steps.create_new_tag.outputs.tag }}
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 2
+      - uses: salsify/action-detect-and-tag-new-version@v2
+        id: create_new_tag
+
+  release:
+    name: Create release
+    runs-on: ubuntu-latest
+    needs: tag
+    if: needs.tag.outputs.tag_name
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/create-release@v1
+        id: create_release
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: ${{ needs.tag.outputs.tag_name }}
+          release_name: ${{ needs.tag.outputs.tag_name }}
+          draft: false
+          prerelease: false
+
+  publish:
+    name: Build and publish
+    runs-on: ubuntu-latest
+    needs: tag
+    if: needs.tag.outputs.tag_name
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: '14.x'
+          registry-url: 'https://registry.npmjs.org'
+      - run: yarn
+      - run: yarn build
+      - run: npm publish --access public
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}

packages/smock/.gitignore

+node_modules/
+cache/
+artifacts/
+build/
+.DS_Store
+temp/
\ No newline at end of file

packages/smock/hardhat.config.ts

+import { HardhatUserConfig } from 'hardhat/config'
+
+import '@nomiclabs/hardhat-ethers'
+import '@nomiclabs/hardhat-waffle'
+
+const config: HardhatUserConfig = {
+  paths: {
+    sources: './test/contracts',
+  },
+  solidity: {
+    version: '0.7.6',
+    settings: {
+      outputSelection: {
+        '*': {
+          '*': ['storageLayout'],
+        },
+      },
+    },
+  },
+}
+
+export default config

packages/smock/package.json

+{
+  "name": "@eth-optimism/smock",
+  "version": "1.0.0-alpha.3",
+  "main": "dist/index",
+  "types": "dist/index",
+  "files": [
+    "dist"
+  ],
+  "license": "MIT",
+  "scripts": {
+    "build": "tsc -p tsconfig.build.json",
+    "test": "hardhat test --show-stack-traces",
+    "lint": "yarn lint:fix && yarn lint:check",
+    "lint:check": "tslint --format stylish --project .",
+    "lint:fix": "prettier --config ./prettier-config.json --write \"hardhat.config.ts\" \"{src,test}/**/*.ts\"",
+    "clean": "rimraf ./artifacts ./cache ./dist"
+  },
+  "peerDependencies": {
+    "@nomiclabs/ethereumjs-vm": "^4",
+    "@nomiclabs/hardhat-ethers": "^2",
+    "ethers": "^5",
+    "hardhat": "^2"
+  },
+  "dependencies": {
+    "@eth-optimism/core-utils": "0.1.10",
+    "@ethersproject/abi": "^5.0.13",
+    "@ethersproject/abstract-provider": "^5.0.10",
+    "bn.js": "^5.2.0"
+  },
+  "devDependencies": {
+    "@nomiclabs/ethereumjs-vm": "4.2.2",
+    "@eth-optimism/dev": "^1.1.1",
+    "@nomiclabs/hardhat-ethers": "^2.0.2",
+    "@nomiclabs/hardhat-waffle": "^2.0.1",
+    "@types/lodash": "^4.14.161",
+    "chai": "^4.3.0",
+    "ethereum-waffle": "^3.3.0",
+    "ethers": "^5.0.32",
+    "glob": "^7.1.6",
+    "hardhat": "^2.1.1",
+    "lodash": "^4.17.20",
+    "prettier": "^2.2.1"
+  }
+}

packages/smock/prettier-config.json

+../../prettier-config.json
\ No newline at end of file

packages/smock/src/common/hardhat-common.ts

+/* Imports: External */
+import { HardhatRuntimeEnvironment } from 'hardhat/types'
+import { HardhatNetworkProvider } from 'hardhat/internal/hardhat-network/provider/provider'
+
+/**
+ * Finds the "base" Ethereum provider of the current hardhat environment.
+ *
+ * Basically, hardhat uses a system of nested providers where each provider wraps the next and
+ * "provides" some extra features. When you're running on top of the "hardhat evm" the bottom of
+ * this series of providers is the "HardhatNetworkProvider":
+ * https://github.com/nomiclabs/hardhat/blob/master/packages/hardhat-core/src/internal/hardhat-network/provider/provider.ts
+ * This object has direct access to the node (provider._node), which in turn has direct access to
+ * the ethereumjs-vm instance (provider._node._vm). So it's quite useful to be able to find this
+ * object reliably!
+ * @param hre hardhat runtime environment to pull the base provider from.
+ * @return base hardhat network provider
+ */
+export const findBaseHardhatProvider = (
+  runtime: HardhatRuntimeEnvironment
+): HardhatNetworkProvider => {
+  // This function is pretty approximate. Haven't spent enough time figuring out if there's a more
+  // reliable way to get the base provider. I can imagine a future in which there's some circular
+  // references and this function ends up looping. So I'll just preempt this by capping the maximum
+  // search depth.
+  const maxLoopIterations = 1024
+  let currentLoopIterations = 0
+
+  // Search by looking for the internal "_wrapped" variable. Base provider doesn't have this
+  // property (at least for now!).
+  let provider = runtime.network.provider
+  while ((provider as any)._wrapped !== undefined) {
+    provider = (provider as any)._wrapped
+
+    // Just throw if we ever end up in (what seems to be) an infinite loop.
+    currentLoopIterations += 1
+    if (currentLoopIterations > maxLoopIterations) {
+      throw new Error(
+        `[smock]: unable to find base hardhat provider. are you sure you're running locally?`
+      )
+    }
+  }
+
+  // TODO: Figure out a reliable way to do a type check here. Source for inspiration:
+  // https://github.com/nomiclabs/hardhat/blob/master/packages/hardhat-core/src/internal/hardhat-network/provider/provider.ts
+  return provider as any
+}

packages/smock/src/common/index.ts

+export * from './hardhat-common'

packages/smock/src/index.ts

+export * from './smockit'
+export * from './smoddit'

packages/smock/src/smockit/binding.ts

+/* Imports: External */
+import { TransactionExecutionError } from 'hardhat/internal/hardhat-network/provider/errors'
+import { HardhatNetworkProvider } from 'hardhat/internal/hardhat-network/provider/provider'
+import { decodeRevertReason } from 'hardhat/internal/hardhat-network/stack-traces/revert-reasons'
+import { VmError } from '@nomiclabs/ethereumjs-vm/dist/exceptions'
+import { toHexString, fromHexString } from '@eth-optimism/core-utils'
+import BN from 'bn.js'
+
+/* Imports: Internal */
+import { MockContract, SmockedVM } from './types'
+
+/**
+ * Checks to see if smock has been initialized already. Basically just checking to see if we've
+ * attached smock state to the VM already.
+ * @param provider Base hardhat network provider to check.
+ * @return Whether or not the provider has already been modified to support smock.
+ */
+const isSmockInitialized = (provider: HardhatNetworkProvider): boolean => {
+  return (provider as any)._node._vm._smockState !== undefined
+}
+
+/**
+ * Modifies a hardhat provider to be compatible with smock.
+ * @param provider Base hardhat network provider to modify.
+ */
+const initializeSmock = (provider: HardhatNetworkProvider): void => {
+  if (isSmockInitialized(provider)) {
+    return
+  }
+
+  // Will need to reference these things.
+  const node = (provider as any)._node
+  const vm: SmockedVM = node._vm
+
+  // Attach some extra state to the VM.
+  vm._smockState = {
+    mocks: {},
+    calls: {},
+    messages: [],
+  }
+
+  // Wipe out our list of calls before each transaction.
+  vm.on('beforeTx', () => {
+    vm._smockState.calls = {}
+  })
+
+  // Watch for new EVM messages (call frames).
+  vm.on('beforeMessage', (message: any) => {
+    // Happens with contract creations. If the current message is a contract creation then it can't
+    // be a call to a smocked contract.
+    if (!message.to) {
+      return
+    }
+
+    const target = toHexString(message.to).toLowerCase()
+
+    // Check if the target address is a smocked contract.
+    if (!(target in vm._smockState.mocks)) {
+      return
+    }
+
+    // Initialize the array of calls to this smock if not done already.
+    if (!(target in vm._smockState.calls)) {
+      vm._smockState.calls[target] = []
+    }
+
+    // Record this message for later.
+    vm._smockState.calls[target].push(message.data)
+    vm._smockState.messages.push(message)
+  })
+
+  // Now *this* is a hack.
+  // Ethereumjs-vm passes `result` by *reference* into the `afterMessage` event. Mutating the
+  // `result` object here will actually mutate the result in the VM. Magic.
+  vm.on('afterMessage', async (result: any) => {
+    // We currently defer to contract creations, meaning we'll "unsmock" an address if a user
+    // later creates a contract at that address. Not sure how to handle this case. Very open to
+    // ideas.
+    if (result.createdAddress) {
+      const created = toHexString(result.createdAddress).toLowerCase()
+      if (created in vm._smockState.mocks) {
+        delete vm._smockState.mocks[created]
+      }
+    }
+
+    // Check if we have messages that need to be handled.
+    if (vm._smockState.messages.length === 0) {
+      return
+    }
+
+    // Handle the last message that was pushed to the array of messages. This works because smock
+    // contracts never create new sub-calls (meaning this `afterMessage` event corresponds directly
+    // to a `beforeMessage` event emitted during a call to a smock contract).
+    const message = vm._smockState.messages.pop()
+    const target = toHexString(message.to).toLowerCase()
+
+    // Not sure if this can ever actually happen? Just being safe.
+    if (!(target in vm._smockState.mocks)) {
+      return
+    }
+
+    // Compute the mock return data.
+    const mock: MockContract = vm._smockState.mocks[target]
+    const {
+      resolve,
+      functionName,
+      rawReturnValue,
+      returnValue,
+      gasUsed,
+    } = await mock._smockit(message.data)
+
+    // Set the mock return data, potentially set the `exceptionError` field if the user requested
+    // a revert.
+    result.gasUsed = new BN(gasUsed)
+    result.execResult.returnValue = returnValue
+    result.execResult.gasUsed = new BN(gasUsed)
+    result.execResult.exceptionError =
+      resolve === 'revert' ? new VmError('smocked revert' as any) : undefined
+  })
+
+  // Here we're fixing with hardhat's internal error management. Smock is a bit weird and messes
+  // with stack traces so we need to help hardhat out a bit when it comes to smock-specific
+  // errors.
+  const originalManagerErrorsFn = node._manageErrors.bind(node)
+  node._manageErrors = async (
+    vmResult: any,
+    vmTrace: any,
+    vmTracerError?: any
+  ): Promise<any> => {
+    if (
+      vmResult.exceptionError &&
+      vmResult.exceptionError.error === 'smocked revert'
+    ) {
+      return new TransactionExecutionError(
+        `VM Exception while processing transaction: revert ${decodeRevertReason(
+          vmResult.returnValue
+        )}`
+      )
+    }
+
+    return originalManagerErrorsFn(vmResult, vmTrace, vmTracerError)
+  }
+}
+
+/**
+ * Attaches a smocked contract to a hardhat network provider. Will also modify the provider to be
+ * compatible with smock if not done already.
+ * @param mock Smocked contract to attach to a provider.
+ * @param provider Hardhat network provider to attach the contract to.
+ */
+export const bindSmock = async (
+  mock: MockContract,
+  provider: HardhatNetworkProvider
+): Promise<void> => {
+  if (!isSmockInitialized(provider)) {
+    initializeSmock(provider)
+  }
+
+  const vm: SmockedVM = (provider as any)._node._vm
+  const pStateManager = vm.pStateManager
+
+  // Add mock to our list of mocks currently attached to the VM.
+  vm._smockState.mocks[mock.address.toLowerCase()] = mock
+
+  // Set the contract code for our mock to 0x00 == STOP. Need some non-empty contract code because
+  // Solidity will sometimes throw if it's calling something without code (I forget the exact
+  // scenario that causes this throw).
+  await pStateManager.putContractCode(
+    fromHexString(mock.address),
+    Buffer.from('00', 'hex')
+  )
+}

packages/smock/src/smockit/index.ts

+export * from './smockit'
+export * from './types'

packages/smock/src/smockit/smockit.ts

+/* Imports: External */
+import hre from 'hardhat'
+import { Contract, ContractFactory, ethers } from 'ethers'
+import { toHexString, fromHexString } from '@eth-optimism/core-utils'
+
+/* Imports: Internal */
+import {
+  isArtifact,
+  MockContract,
+  MockContractFunction,
+  MockReturnValue,
+  SmockedVM,
+  SmockOptions,
+  SmockSpec,
+} from './types'
+import { bindSmock } from './binding'
+import { makeRandomAddress } from '../utils'
+import { findBaseHardhatProvider } from '../common'
+
+/**
+ * Generates an ethers Interface instance when given a smock spec. Meant for standardizing the
+ * various input types we might reasonably want to support.
+ * @param spec Smock specification object. Thing you want to base the interface on.
+ * @param hre Hardhat runtime environment. Used so we can
+ * @return Interface generated from the spec.
+ */
+const makeContractInterfaceFromSpec = async (
+  spec: SmockSpec
+): Promise<ethers.utils.Interface> => {
+  if (spec instanceof Contract) {
+    return spec.interface
+  } else if (spec instanceof ContractFactory) {
+    return spec.interface
+  } else if (spec instanceof ethers.utils.Interface) {
+    return spec
+  } else if (isArtifact(spec)) {
+    return new ethers.utils.Interface(spec.abi)
+  } else if (typeof spec === 'string') {
+    try {
+      return new ethers.utils.Interface(spec)
+    } catch (err) {
+      return (await hre.ethers.getContractFactory(spec)).interface
+    }
+  } else {
+    return new ethers.utils.Interface(spec)
+  }
+}
+
+/**
+ * Creates a mock contract function from a real contract function.
+ * @param contract Contract object to make a mock function for.
+ * @param functionName Name of the function to mock.
+ * @param vm Virtual machine reference, necessary for call assertions to work.
+ * @return Mock contract function.
+ */
+const smockifyFunction = (
+  contract: Contract,
+  functionName: string,
+  vm: SmockedVM
+): MockContractFunction => {
+  return {
+    reset: () => {
+      return
+    },
+    get calls() {
+      return vm._smockState.calls[contract.address.toLowerCase()]
+        .map((calldataBuf: Buffer) => {
+          const sighash = toHexString(calldataBuf.slice(0, 4))
+          const fragment = contract.interface.getFunction(sighash)
+
+          let data: any = toHexString(calldataBuf)
+          try {
+            data = contract.interface.decodeFunctionData(fragment.name, data)
+          } catch (e) {
+            console.error(e)
+          }
+
+          return {
+            functionName: fragment.name,
+            data,
+          }
+        })
+        .filter((functionResult: any) => {
+          return functionResult.functionName === functionName
+        })
+        .map((functionResult: any) => {
+          return functionResult.data
+        })
+    },
+    will: {
+      get return() {
+        const fn: any = () => {
+          this.resolve = 'return'
+          this.returnValue = undefined
+        }
+
+        fn.with = (returnValue?: MockReturnValue): void => {
+          this.resolve = 'return'
+          this.returnValue = returnValue
+        }
+
+        return fn
+      },
+      get revert() {
+        const fn: any = () => {
+          this.resolve = 'revert'
+          this.returnValue = undefined
+        }
+
+        fn.with = (revertValue?: string): void => {
+          this.resolve = 'revert'
+          this.returnValue = revertValue
+        }
+
+        return fn
+      },
+      resolve: 'return',
+    },
+  }
+}
+
+/**
+ * Turns a specification into a mock contract.
+ * @param spec Smock contract specification.
+ * @param opts Optional additional settings.
+ */
+export const smockit = async (
+  spec: SmockSpec,
+  opts: SmockOptions = {}
+): Promise<MockContract> => {
+  // Only support native hardhat runtime, haven't bothered to figure it out for anything else.
+  if (hre.network.name !== 'hardhat') {
+    throw new Error(
+      `[smock]: smock is only compatible with the "hardhat" network, got: ${hre.network.name}`
+    )
+  }
+
+  // Find the provider object. See comments for `findBaseHardhatProvider`
+  const provider = findBaseHardhatProvider(hre)
+
+  // Sometimes the VM hasn't been initialized by the time we get here, depending on what the user
+  // is doing with hardhat (e.g., sending a transaction before calling this function will
+  // initialize the vm). Initialize it here if it hasn't been already.
+  if ((provider as any)._node === undefined) {
+    await (provider as any)._init()
+  }
+
+  // Generate the contract object that we're going to attach our fancy functions to. Doing it this
+  // way is nice because it "feels" more like a contract (as long as you're using ethers).
+  const contract = new ethers.Contract(
+    opts.address || makeRandomAddress(),
+    await makeContractInterfaceFromSpec(spec),
+    opts.provider || hre.ethers.provider // TODO: Probably check that this exists.
+  ) as MockContract
+
+  // Start by smocking the fallback.
+  contract.smocked = {
+    fallback: smockifyFunction(
+      contract,
+      'fallback',
+      (provider as any)._node._vm
+    ),
+  }
+
+  // Smock the rest of the contract functions.
+  for (const functionName of Object.keys(contract.functions)) {
+    contract.smocked[functionName] = smockifyFunction(
+      contract,
+      functionName,
+      (provider as any)._node._vm
+    )
+  }
+
+  // TODO: Make this less of a hack.
+  ;(contract as any)._smockit = async function (
+    data: Buffer
+  ): Promise<{
+    resolve: 'return' | 'revert'
+    functionName: string
+    rawReturnValue: any
+    returnValue: Buffer
+    gasUsed: number
+  }> {
+    let fn: any
+    try {
+      const sighash = toHexString(data.slice(0, 4))
+      fn = this.interface.getFunction(sighash)
+    } catch (err) {
+      fn = null
+    }
+
+    let params: any
+    let mockFn: any
+    if (fn !== null) {
+      params = this.interface.decodeFunctionData(fn, toHexString(data))
+      mockFn = this.smocked[fn.name]
+    } else {
+      params = toHexString(data)
+      mockFn = this.smocked.fallback
+    }
+
+    const rawReturnValue =
+      mockFn.will?.returnValue instanceof Function
+        ? await mockFn.will.returnValue(...params)
+        : mockFn.will.returnValue
+
+    let encodedReturnValue: string = '0x'
+    if (rawReturnValue !== undefined) {
+      if (mockFn.will?.resolve === 'revert') {
+        if (typeof rawReturnValue !== 'string') {
+          throw new Error(
+            `Smock: Tried to revert with a non-string (or non-bytes) type: ${typeof rawReturnValue}`
+          )
+        }
+
+        if (rawReturnValue.startsWith('0x')) {
+          encodedReturnValue = rawReturnValue
+        } else {
+          const errorface = new ethers.utils.Interface([
+            {
+              inputs: [
+                {
+                  name: '_reason',
+                  type: 'string',
+                },
+              ],
+              name: 'Error',
+              outputs: [],
+              stateMutability: 'nonpayable',
+              type: 'function',
+            },
+          ])
+
+          encodedReturnValue = errorface.encodeFunctionData('Error', [
+            rawReturnValue,
+          ])
+        }
+      } else {
+        if (fn === null) {
+          encodedReturnValue = rawReturnValue
+        } else {
+          try {
+            encodedReturnValue = this.interface.encodeFunctionResult(fn, [
+              rawReturnValue,
+            ])
+          } catch (err) {
+            if (err.code === 'INVALID_ARGUMENT') {
+              try {
+                encodedReturnValue = this.interface.encodeFunctionResult(
+                  fn,
+                  rawReturnValue
+                )
+              } catch {
+                if (typeof rawReturnValue !== 'string') {
+                  throw new Error(
+                    `Could not properly encode mock return value for ${fn.name}`
+                  )
+                }
+
+                encodedReturnValue = rawReturnValue
+              }
+            } else {
+              throw err
+            }
+          }
+        }
+      }
+    } else {
+      if (fn === null) {
+        encodedReturnValue = '0x'
+      } else {
+        encodedReturnValue = '0x' + '00'.repeat(2048)
+      }
+    }
+
+    return {
+      resolve: mockFn.will?.resolve,
+      functionName: fn ? fn.name : null,
+      rawReturnValue,
+      returnValue: fromHexString(encodedReturnValue),
+      gasUsed: mockFn.gasUsed || 0,
+    }
+  }
+
+  await bindSmock(contract, provider)
+
+  return contract
+}

packages/smock/src/smockit/types.ts

+/* Imports: External */
+import { Artifact } from 'hardhat/types'
+import { Contract, ContractFactory, ethers } from 'ethers'
+import { Provider } from '@ethersproject/abstract-provider'
+import { JsonFragment, Fragment } from '@ethersproject/abi'
+
+export type SmockSpec =
+  | Artifact
+  | Contract
+  | ContractFactory
+  | ethers.utils.Interface
+  | string
+  | (JsonFragment | Fragment | string)[]
+
+export interface SmockOptions {
+  provider?: Provider
+  address?: string
+}
+
+export type MockReturnValue =
+  | string
+  | Object
+  | any[]
+  | ((...params: any[]) => MockReturnValue)
+
+export interface MockContractFunction {
+  calls: any[]
+
+  reset: () => void
+
+  will: {
+    return: {
+      (): void
+      with: (returnValue?: MockReturnValue) => void
+    }
+    revert: {
+      (): void
+      with: (
+        revertValue?: string | (() => string) | (() => Promise<string>)
+      ) => void
+    }
+    resolve: 'return' | 'revert'
+  }
+}
+
+export type MockContract = Contract & {
+  smocked: {
+    [name: string]: MockContractFunction
+  }
+}
+
+export interface SmockedVM {
+  _smockState: {
+    mocks: {
+      [address: string]: MockContract
+    }
+    calls: {
+      [address: string]: any[]
+    }
+    messages: any[]
+  }
+
+  on: (event: string, callback: Function) => void
+
+  pStateManager: {
+    putContractCode: (address: Buffer, code: Buffer) => Promise<void>
+  }
+}
+
+const isMockFunction = (obj: any): obj is MockContractFunction => {
+  return (
+    obj &&
+    obj.will &&
+    obj.will.return &&
+    obj.will.return.with &&
+    obj.will.revert &&
+    obj.will.revert.with
+    // TODO: obj.will.emit
+  )
+}
+
+export const isMockContract = (obj: any): obj is MockContract => {
+  return (
+    obj &&
+    obj.smocked &&
+    obj.smocked.fallback &&
+    Object.values(obj.smocked).every((smockFunction: any) => {
+      return isMockFunction(smockFunction)
+    })
+  )
+}
+
+export const isArtifact = (obj: any): obj is Artifact => {
+  return (
+    obj &&
+    typeof obj._format === 'string' &&
+    typeof obj.contractName === 'string' &&
+    typeof obj.sourceName === 'string' &&
+    Array.isArray(obj.abi) &&
+    typeof obj.bytecode === 'string' &&
+    typeof obj.deployedBytecode === 'string' &&
+    obj.linkReferences &&
+    obj.deployedLinkReferences
+  )
+}

packages/smock/src/smoddit/binding.ts

+/* External Imports */
+import { toHexString, fromHexString } from '@eth-optimism/core-utils'
+import { HardhatNetworkProvider } from 'hardhat/internal/hardhat-network/provider/provider'
+
+/* Internal Imports */
+import { ModifiableContract } from './types'
+
+/**
+ * Checks to see if smoddit has been initialized already.
+ * @param provider Base hardhat network provider to check.
+ * @return Whether or not the provider has already been modified to support smoddit.
+ */
+const isSmodInitialized = (provider: HardhatNetworkProvider): boolean => {
+  return (provider as any)._node._vm._smod !== undefined
+}
+
+/**
+ * Initializes smodding functionality.
+ * @param provider Base hardhat network provider to modify.
+ */
+const initializeSmod = (provider: HardhatNetworkProvider): void => {
+  if (isSmodInitialized(provider)) {
+    return
+  }
+
+  // Will need to reference these things.
+  const node = (provider as any)._node
+  const vm = node._vm
+  const pStateManager = vm.pStateManager
+
+  vm._smod = {
+    contracts: {},
+  }
+
+  const originalGetStorageFn = pStateManager.getContractStorage.bind(
+    pStateManager
+  )
+  pStateManager.getContractStorage = async (
+    addressBuf: Buffer,
+    keyBuf: Buffer
+  ): Promise<Buffer> => {
+    const originalReturnValue = await originalGetStorageFn(addressBuf, keyBuf)
+
+    const address = toHexString(addressBuf).toLowerCase()
+    const key = toHexString(keyBuf).toLowerCase()
+
+    if (!(address in vm._smod.contracts)) {
+      return originalReturnValue
+    }
+
+    const contract: ModifiableContract = vm._smod.contracts[address]
+    if (!(key in contract._smodded)) {
+      return originalReturnValue
+    }
+
+    return fromHexString(contract._smodded[key])
+  }
+
+  const originalPutStorageFn = pStateManager.putContractStorage.bind(
+    pStateManager
+  )
+  pStateManager.putContractStorage = async (
+    addressBuf: Buffer,
+    keyBuf: Buffer,
+    valBuf: Buffer
+  ): Promise<void> => {
+    await originalPutStorageFn(addressBuf, keyBuf, valBuf)
+
+    const address = toHexString(addressBuf).toLowerCase()
+    const key = toHexString(keyBuf).toLowerCase()
+
+    if (!(address in vm._smod.contracts)) {
+      return
+    }
+
+    const contract: ModifiableContract = vm._smod.contracts[address]
+    if (!(key in contract._smodded)) {
+      return
+    }
+
+    delete contract._smodded[key]
+  }
+}
+
+/**
+ * Binds the smodded contract to the VM.
+ * @param contract Contract to bind.
+ */
+export const bindSmod = (
+  contract: ModifiableContract,
+  provider: HardhatNetworkProvider
+): void => {
+  if (!isSmodInitialized(provider)) {
+    initializeSmod(provider)
+  }
+
+  const vm = (provider as any)._node._vm
+
+  // Add mock to our list of mocks currently attached to the VM.
+  vm._smod.contracts[contract.address.toLowerCase()] = contract
+}

packages/smock/src/smoddit/index.ts

+export * from './smoddit'
+export * from './types'

packages/smock/src/smoddit/smoddit.ts

+/* External Imports */
+import hre from 'hardhat'
+import { fromHexString } from '@eth-optimism/core-utils'
+
+/* Internal Imports */
+import { ModifiableContract, ModifiableContractFactory, Smodify } from './types'
+import { getStorageLayout, getStorageSlots } from './storage'
+import { bindSmod } from './binding'
+import { toHexString32 } from '../utils'
+import { findBaseHardhatProvider } from '../common'
+
+/**
+ * Creates a modifiable contract factory.
+ * @param name Name of the contract to smoddify.
+ * @param signer Optional signer to attach to the factory.
+ * @returns Smoddified contract factory.
+ */
+export const smoddit = async (
+  name: string,
+  signer?: any
+): Promise<ModifiableContractFactory> => {
+  // Find the provider object. See comments for `findBaseHardhatProvider`
+  const provider = findBaseHardhatProvider(hre)
+
+  // Sometimes the VM hasn't been initialized by the time we get here, depending on what the user
+  // is doing with hardhat (e.g., sending a transaction before calling this function will
+  // initialize the vm). Initialize it here if it hasn't been already.
+  if ((provider as any)._node === undefined) {
+    await (provider as any)._init()
+  }
+
+  // Pull out a reference to the vm's state manager.
+  const pStateManager = (provider as any)._node._vm.pStateManager
+
+  const layout = await getStorageLayout(name)
+  const factory = (await hre.ethers.getContractFactory(
+    name,
+    signer
+  )) as ModifiableContractFactory
+
+  const originalDeployFn = factory.deploy.bind(factory)
+  factory.deploy = async (...args: any[]): Promise<ModifiableContract> => {
+    const contract: ModifiableContract = await originalDeployFn(...args)
+    contract._smodded = {}
+
+    const put = (storage: any) => {
+      if (!storage) {
+        return
+      }
+
+      const slots = getStorageSlots(layout, storage)
+      for (const slot of slots) {
+        contract._smodded[slot.hash.toLowerCase()] = slot.value
+      }
+    }
+
+    const reset = () => {
+      contract._smodded = {}
+    }
+
+    const set = (storage: any) => {
+      contract.smodify.reset()
+      contract.smodify.put(storage)
+    }
+
+    const check = async (storage: any) => {
+      if (!storage) {
+        return true
+      }
+
+      const slots = getStorageSlots(layout, storage)
+      return slots.every(async (slot) => {
+        return (
+          toHexString32(
+            await pStateManager.getContractStorage(
+              fromHexString(contract.address),
+              fromHexString(slot.hash.toLowerCase())
+            )
+          ) === slot.value
+        )
+      })
+    }
+
+    contract.smodify = {
+      put,
+      reset,
+      set,
+      check,
+    }
+
+    bindSmod(contract, provider)
+    return contract
+  }
+
+  return factory
+}

packages/smock/src/smoddit/storage.ts

+/* External Imports */
+import hre from 'hardhat'
+import { Artifacts } from 'hardhat/internal/artifacts'
+import { ethers } from 'ethers'
+import { remove0x } from '@eth-optimism/core-utils'
+import _ from 'lodash'
+
+/* Internal Imports */
+import { toHexString32 } from '../utils'
+
+interface InputSlot {
+  label: string
+  slot: number
+}
+
+interface StorageSlot {
+  label: string
+  hash: string
+  value: string
+}
+
+/**
+ * Reads the storage layout of a contract.
+ * @param name Name of the contract to get a storage layout for.
+ * @return Storage layout for the given contract name.
+ */
+export const getStorageLayout = async (name: string): Promise<any> => {
+  const artifacts = new Artifacts(hre.config.paths.artifacts)
+  const { sourceName, contractName } = artifacts.readArtifactSync(name)
+  const buildInfo = await hre.artifacts.getBuildInfo(
+    `${sourceName}:${contractName}`
+  )
+  const output = buildInfo.output.contracts[sourceName][contractName]
+
+  if (!('storageLayout' in output)) {
+    throw new Error(
+      `Storage layout for ${name} not found. Did you forget to set the storage layout compiler option in your hardhat config? Read more: https://github.com/ethereum-optimism/smock#note-on-using-smoddit`
+    )
+  }
+
+  return (output as any).storageLayout
+}
+
+/**
+ * Converts storage into a list of storage slots.
+ * @param storageLayout Contract storage layout.
+ * @param obj Storage object to convert.
+ * @returns List of storage slots.
+ */
+export const getStorageSlots = (
+  storageLayout: any,
+  obj: any
+): StorageSlot[] => {
+  const slots: StorageSlot[] = []
+  const flat = flattenObject(obj)
+
+  for (const key of Object.keys(flat)) {
+    const path = key.split('.')
+    const variableLabel = path[0]
+
+    const variableDef = storageLayout.storage.find((vDef: any) => {
+      return vDef.label === variableLabel
+    })
+
+    if (!variableDef) {
+      throw new Error(
+        `Could not find a matching variable definition for ${variableLabel}`
+      )
+    }
+
+    const baseSlot = parseInt(variableDef.slot, 10)
+    const baseDepth = (variableDef.type.match(/t_mapping/g) || []).length
+    const slotLabel =
+      path.length > 1 + baseDepth ? path[path.length - 1] : 'default'
+
+    const inputSlot = getInputSlots(storageLayout, variableDef.type).find(
+      (iSlot) => {
+        return iSlot.label === slotLabel
+      }
+    )
+
+    if (!inputSlot) {
+      throw new Error(
+        `Could not find a matching slot definition for ${slotLabel}`
+      )
+    }
+
+    let slotHash = toHexString32(baseSlot)
+    for (let i = 0; i < baseDepth; i++) {
+      slotHash = ethers.utils.keccak256(
+        toHexString32(path[i + 1]) + remove0x(slotHash)
+      )
+    }
+
+    slotHash = toHexString32(
+      ethers.BigNumber.from(slotHash).add(inputSlot.slot)
+    )
+
+    slots.push({
+      label: key,
+      hash: slotHash,
+      value: toHexString32(flat[key]),
+    })
+  }
+
+  return slots
+}
+
+/**
+ * Flattens an object.
+ * @param obj Object to flatten.
+ * @param prefix Current object prefix (used recursively).
+ * @param res Current result (used recursively).
+ * @returns Flattened object.
+ */
+const flattenObject = (
+  obj: any,
+  prefix: string = '',
+  res: any = {}
+): Object => {
+  if (ethers.BigNumber.isBigNumber(obj)) {
+    res[prefix] = obj.toNumber()
+    return res
+  } else if (_.isString(obj) || _.isNumber(obj) || _.isBoolean(obj)) {
+    res[prefix] = obj
+    return res
+  } else if (_.isArray(obj)) {
+    for (let i = 0; i < obj.length; i++) {
+      const pre = _.isEmpty(prefix) ? `${i}` : `${prefix}.${i}`
+      flattenObject(obj[i], pre, res)
+    }
+    return res
+  } else if (_.isPlainObject(obj)) {
+    for (const key of Object.keys(obj)) {
+      const pre = _.isEmpty(prefix) ? key : `${prefix}.${key}`
+      flattenObject(obj[key], pre, res)
+    }
+    return res
+  } else {
+    throw new Error('Cannot flatten unsupported object type.')
+  }
+}
+
+/**
+ * Gets the slot positions for a provided variable type.
+ * @param storageLayout Contract's storage layout.
+ * @param inputTypeName Variable type name.
+ * @returns Slot positions.
+ */
+const getInputSlots = (
+  storageLayout: any,
+  inputTypeName: string
+): InputSlot[] => {
+  const inputType = storageLayout.types[inputTypeName]
+
+  if (inputType.encoding === 'mapping') {
+    return getInputSlots(storageLayout, inputType.value)
+  } else if (inputType.encoding === 'inplace') {
+    if (inputType.members) {
+      return inputType.members.map((member: any) => {
+        return {
+          label: member.label,
+          slot: member.slot,
+        }
+      })
+    } else {
+      return [
+        {
+          label: 'default',
+          slot: 0,
+        },
+      ]
+    }
+  } else {
+    throw new Error(`Encoding type not supported: ${inputType.encoding}`)
+  }
+}

packages/smock/src/smoddit/types.ts

+/* External Imports */
+import { Contract, ContractFactory } from 'ethers'
+
+export interface Smodify {
+  put: (storage: any) => void
+  set: (storage: any) => void
+  check: (storage: any) => Promise<boolean>
+  reset: () => void
+}
+
+export interface Smodded {
+  [hash: string]: string
+}
+
+export interface ModifiableContract extends Contract {
+  smodify: Smodify
+  _smodded: Smodded
+}
+
+export interface ModifiableContractFactory extends ContractFactory {
+  deploy: (...args: any[]) => Promise<ModifiableContract>
+}

packages/smock/src/utils/address-utils.ts

+import { ethers } from 'ethers'
+
+export const makeRandomAddress = (): string => {
+  return ethers.utils.getAddress(
+    '0x' +
+      [...Array(40)]
+        .map(() => {
+          return Math.floor(Math.random() * 16).toString(16)
+        })
+        .join('')
+  )
+}

packages/smock/src/utils/hex-utils.ts

+/* External Imports */
+import { BigNumber } from 'ethers'
+import { remove0x } from '@eth-optimism/core-utils'
+
+export const toHexString32 = (
+  value: string | number | BigNumber | boolean
+): string => {
+  if (typeof value === 'string' && value.startsWith('0x')) {
+    return '0x' + remove0x(value).padStart(64, '0').toLowerCase()
+  } else if (typeof value === 'boolean') {
+    return toHexString32(value ? 1 : 0)
+  } else {
+    return toHexString32(BigNumber.from(value).toHexString())
+  }
+}

packages/smock/src/utils/index.ts

+export * from './hex-utils'
+export * from './address-utils'

packages/smock/test/contracts/SimpleStorageGetter.sol

+// SPDX-License-Identifier: MIT
+pragma solidity ^0.7.0;
+pragma experimental ABIEncoderV2;
+
+contract SimpleStorageGetter {
+    struct SimpleStruct {
+        uint256 valueA;
+        bool valueB;
+    }
+
+    uint256 internal _constructorUint256;
+    uint256 internal _uint256;
+    bool internal _bool;
+    SimpleStruct internal _SimpleStruct;
+    mapping (uint256 => uint256) _uint256Map;
+    mapping (uint256 => mapping (uint256 => uint256)) _uint256NestedMap;
+
+    constructor(
+        uint256 _inA
+    ) {
+        _constructorUint256 = _inA;
+    }
+
+    function getConstructorUint256()
+        public
+        view
+        returns (
+            uint256 _out
+        )
+    {
+        return _constructorUint256;
+    }
+
+    function getUint256()
+        public
+        view
+        returns (
+            uint256 _out
+        )
+    {
+        return _uint256;
+    }
+
+    function setUint256(
+        uint256 _in
+    )
+        public
+    {
+        _uint256 = _in;
+    }
+
+    function getBool()
+        public
+        view
+        returns (
+            bool _out
+        )
+    {
+        return _bool;
+    }
+
+    function getSimpleStruct()
+        public
+        view
+        returns (
+            SimpleStruct memory _out
+        )
+    {
+        return _SimpleStruct;
+    }
+
+    function getUint256MapValue(
+        uint256 _key
+    )
+        public
+        view
+        returns (
+            uint256 _out
+        )
+    {
+        return _uint256Map[_key];
+    }
+
+    function getNestedUint256MapValue(
+        uint256 _keyA,
+        uint256 _keyB
+    )
+        public
+        view
+        returns (
+            uint256 _out
+        )
+    {
+        return _uint256NestedMap[_keyA][_keyB];
+    }
+}

packages/smock/test/contracts/TestHelpers_BasicReturnContract.sol

+// SPDX-License-Identifier: MIT
+pragma solidity ^0.7.0;
+pragma experimental ABIEncoderV2;
+
+contract TestHelpers_BasicReturnContract {
+    fallback()
+        external
+    {}
+
+    function empty()
+        public
+    {}
+
+    function getBoolean()
+        public
+        returns (
+            bool _out1
+        )
+    {}
+
+    function getUint256()
+        public
+        returns (
+            uint256 _out1
+        )
+    {}
+
+    function getBytes32()
+        public
+        returns (
+            bytes32 _out1
+        )
+    {}
+
+    function getBytes()
+        public
+        returns (
+            bytes memory _out1
+        )
+    {}
+
+    function getString()
+        public
+        returns (
+            string memory _out1
+        )
+    {}
+
+    function getInputtedBoolean(
+        bool _in1
+    )
+        public
+        returns (
+            bool _out1
+        )
+    {}
+
+    function getInputtedUint256(
+        uint256 _in1
+    )
+        public
+        returns (
+            uint256 _out1
+        )
+    {}
+
+    function getInputtedBytes32(
+        bytes32 _in1
+    )
+        public
+        returns (
+            bytes32 _out1
+        )
+    {}
+
+    struct StructFixedSize {
+        bool valBoolean;
+        uint256 valUint256;
+        bytes32 valBytes32;
+    }
+
+    function getStructFixedSize()
+        public
+        returns (
+            StructFixedSize memory _out1
+        )
+    {}
+
+    struct StructDynamicSize {
+        bytes valBytes;
+        string valString;
+    }
+
+    function getStructDynamicSize()
+        public
+        returns (
+            StructDynamicSize memory _out1
+        )
+    {}
+
+    struct StructMixedSize {
+        bool valBoolean;
+        uint256 valUint256;
+        bytes32 valBytes32;
+        bytes valBytes;
+        string valString;
+    }
+
+    function getStructMixedSize()
+        public
+        returns (
+            StructMixedSize memory _out1
+        )
+    {}
+
+    struct StructNested {
+        StructFixedSize valStructFixedSize;
+        StructDynamicSize valStructDynamicSize;
+    }
+
+    function getStructNested()
+        public
+        returns (
+            StructNested memory _out1
+        )
+    {}
+
+    function getArrayUint256()
+        public
+        returns (
+            uint256[] memory _out
+        )
+    {}
+}

packages/smock/test/contracts/TestHelpers_EmptyContract.sol

+// SPDX-License-Identifier: MIT
+pragma solidity ^0.7.0;
+
+contract TestHelpers_EmptyContract {}

packages/smock/test/smockit/smock-initialization.spec.ts

+/* Imports: External */
+import { ethers, artifacts } from 'hardhat'
+import { expect } from 'chai'
+
+/* Imports: Internal */
+import { smockit, isMockContract } from '../../src'
+
+describe('[smock]: initialization tests', () => {
+  describe('initialization: ethers objects', () => {
+    it('should be able to create a SmockContract from an ethers ContractFactory', async () => {
+      const spec = await ethers.getContractFactory('TestHelpers_EmptyContract')
+      const mock = await smockit(spec)
+
+      expect(isMockContract(mock)).to.be.true
+    })
+
+    it('should be able to create a SmockContract from an ethers Contract', async () => {
+      const factory = await ethers.getContractFactory(
+        'TestHelpers_EmptyContract'
+      )
+
+      const spec = await factory.deploy()
+      const mock = await smockit(spec)
+
+      expect(isMockContract(mock)).to.be.true
+    })
+
+    it('should be able to create a SmockContract from an ethers Interface', async () => {
+      const factory = await ethers.getContractFactory(
+        'TestHelpers_EmptyContract'
+      )
+
+      const spec = factory.interface
+      const mock = await smockit(spec)
+
+      expect(isMockContract(mock)).to.be.true
+    })
+  })
+
+  describe('initialization: other', () => {
+    it('should be able to create a SmockContract from a contract name', async () => {
+      const spec = 'TestHelpers_EmptyContract'
+      const mock = await smockit(spec)
+
+      expect(isMockContract(mock)).to.be.true
+    })
+
+    it('should be able to create a SmockContract from a JSON contract artifact object', async () => {
+      const artifact = await artifacts.readArtifact(
+        'TestHelpers_BasicReturnContract'
+      )
+      const spec = artifact
+      const mock = await smockit(spec)
+
+      expect(isMockContract(mock)).to.be.true
+    })
+
+    it('should be able to create a SmockContract from a JSON contract ABI object', async () => {
+      const artifact = await artifacts.readArtifact(
+        'TestHelpers_BasicReturnContract'
+      )
+      const spec = artifact.abi
+      const mock = await smockit(spec)
+
+      expect(isMockContract(mock)).to.be.true
+    })
+
+    it('should be able to create a SmockContract from a JSON contract ABI string', async () => {
+      const artifact = await artifacts.readArtifact(
+        'TestHelpers_BasicReturnContract'
+      )
+      const spec = JSON.stringify(artifact.abi)
+      const mock = await smockit(spec)
+
+      expect(isMockContract(mock)).to.be.true
+    })
+  })
+})

packages/smock/test/smoddit/smoddit.spec.ts

+/* Imports: External */
+import { expect } from 'chai'
+import { BigNumber } from 'ethers'
+import _ from 'lodash'
+
+/* Imports: Internal */
+import {
+  ModifiableContractFactory,
+  ModifiableContract,
+  smoddit,
+} from '../../src/smoddit'
+
+describe('smoddit', () => {
+  describe('via contract factory', () => {
+    describe('for functions with a single fixed return value', () => {
+      let SmodFactory: ModifiableContractFactory
+      before(async () => {
+        SmodFactory = await smoddit('SimpleStorageGetter')
+      })
+
+      let smod: ModifiableContract
+      beforeEach(async () => {
+        smod = await SmodFactory.deploy(4321)
+      })
+
+      it('should be able to return a uint256', async () => {
+        const ret = 1234
+
+        smod.smodify.put({
+          _uint256: ret,
+        })
+
+        expect(await smod.getUint256()).to.equal(ret)
+      })
+
+      it('should be able to return a boolean', async () => {
+        const ret = true
+
+        smod.smodify.put({
+          _bool: ret,
+        })
+
+        expect(await smod.getBool()).to.equal(ret)
+      })
+
+      it('should be able to return a simple struct', async () => {
+        const ret = {
+          valueA: BigNumber.from(1234),
+          valueB: true,
+        }
+
+        smod.smodify.put({
+          _SimpleStruct: ret,
+        })
+
+        const result = _.toPlainObject(await smod.getSimpleStruct())
+        expect(result.valueA).to.deep.equal(ret.valueA)
+        expect(result.valueB).to.deep.equal(ret.valueB)
+      })
+
+      it('should be able to return a simple uint256 => uint256 mapping value', async () => {
+        const retKey = 1234
+        const retVal = 5678
+
+        smod.smodify.put({
+          _uint256Map: {
+            [retKey]: retVal,
+          },
+        })
+
+        expect(await smod.getUint256MapValue(retKey)).to.equal(retVal)
+      })
+
+      it('should be able to return a nested uint256 => uint256 mapping value', async () => {
+        const retKeyA = 1234
+        const retKeyB = 4321
+        const retVal = 5678
+
+        smod.smodify.put({
+          _uint256NestedMap: {
+            [retKeyA]: {
+              [retKeyB]: retVal,
+            },
+          },
+        })
+
+        expect(await smod.getNestedUint256MapValue(retKeyA, retKeyB)).to.equal(
+          retVal
+        )
+      })
+
+      it('should not return the set value if the value has been changed by the contract', async () => {
+        const ret = 1234
+
+        smod.smodify.put({
+          _uint256: ret,
+        })
+
+        await smod.setUint256(4321)
+
+        expect(await smod.getUint256()).to.equal(4321)
+      })
+
+      it('should return the set value if it was set in the constructor', async () => {
+        const ret = 1234
+
+        smod.smodify.put({
+          _constructorUint256: ret,
+        })
+
+        expect(await smod.getConstructorUint256()).to.equal(1234)
+      })
+    })
+  })
+})

packages/smock/tsconfig.build.json

+{
+  "extends": "../../tsconfig.build.json",
+
+  "compilerOptions": {
+    "outDir": "./dist"
+  },
+
+  "include": [
+    "src/**/*"
+  ],
+  "files": [
+      "./hardhat.config.ts"
+  ]
+}

packages/smock/tsconfig.json

+{
+  "extends": "../../tsconfig.json",
+  "files": [
+      "./hardhat.config.ts"
+  ]
+}

packages/smock/tslint.json

+{
+    "extends": "../../tslint.base.json"
+}

prettier-config.json

+{
+  "$schema": "http://json.schemastore.org/prettierrc",
+  "trailingComma": "es5",
+  "tabWidth": 2,
+  "semi": false,
+  "singleQuote": true,
+  "arrowParens": "always"
+}

tsconfig.base.json

-{
-    "compilerOptions": {
-        "composite": true,
-        "module": "commonjs",
-        "target": "es2017",
-        "declaration": true,
-        "noImplicitAny": false,
-        "removeComments": true,
-        "noLib": false,
-        "emitDecoratorMetadata": true,
-        "experimentalDecorators": true,
-        "sourceMap": true,
-        "outDir": "./build",
-        "lib": [
-            "es7"
-        ],
-        "esModuleInterop": true,
-        "typeRoots": [
-            "node_modules/@types"
-      ]
-    }
-}

tsconfig.build.json

+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "target": "es2017",
+    "sourceMap": true,
+    "esModuleInterop": true,
+    "composite": true,
+    "declaration": true,
+    "noImplicitAny": false,
+    "removeComments": true,
+    "noLib": false,
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "typeRoots": [
+            "node_modules/@types"
+      ]
+  },
+  "exclude": [
+    "node_modules",
+    "dist"
+  ]
+}

tsconfig.json

+{
+  "extends": "./tsconfig.build.json",
+  "compilerOptions": {
+    "baseUrl": ".",
+    "paths": {
+      "@eth-optimism/*": ["packages/*/src"]
+    },
+    "skipLibCheck": true
+  }
+}