Smock is the Solidity mocking library. It’s a plugin for hardhat that can be used to create mock Solidity contracts entirely in JavaScript (or TypeScript!). With Smock, it’s easier than ever to test your smart contracts. You’ll never have to write another mock contract in Solidity again.

Smock is inspired by sinon, sinon-chai, and Python’s unittest.mock. Although Smock is currently only compatible with hardhat, we plan to extend support to other testing frameworks like Truffle.

If you wanna chat about the future of Solidity Mocking, join our Discord!


  • Get rid of your folder of “mock” contracts and just use JavaScript.

  • Keep your tests simple with a sweet set of chai matchers.

  • Fully compatible with TypeScript and TypeChain.

  • Manipulate the behavior of functions on the fly with fakes.

  • Modify functions and internal variables of a real contract with mocks.

  • Make assertions about calls, call arguments, and call counts.

  • We’ve got extensive documentation and a complete test suite.


Detailed documentation can be found here.

Quick Start


You can install Smock via npm or yarn:

npm install @defi-wonderland/smock

Basic Usage

Smock is dead simple to use. Here’s a basic example of how you might use it to streamline your tests.

import { FakeContract, smock } from '@defi-wonderland/smock';

chai.should(); // if you like should syntax

describe('MyContract', () => {
    let myContractFake: FakeContract<MyContract>;

    beforeEach(async () => {
        myContractFake = await smock.fake('MyContract');

    it('some test', () => {
        myContractFake.bark.atCall(0)'Hello World');


Smock is released under the MIT license. Feel free to use, modify, and/or redistribute this software as you see fit. See the LICENSE file for more information.