Testing using Chai & Mocha

(Supported since Remix IDE v0.22.0)

Remix supports testing of your files in JavaScript using assertion library Chai & test framework Mocha

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple and fun.

Write tests

Create a js file in your project workspace. Better to create it inside scripts folder. Lets name it sample.test.js.

Write your tests in the file. Here is a sample:

const { expect } = require("chai");

describe("Sample", function () {
  it("Sample tests with mocha and chai", async function () {
    var foo = 'bar'
    var beverages = { tea: [ 'chai', 'matcha', 'oolong' ] };
    expect(foo).to.be.a('string');
    expect(foo).to.equal('bar');
    expect(foo).to.have.lengthOf(3);
    expect(beverages).to.have.property('tea').with.lengthOf(3);
  });
});

Run tests

Once done with writing the tests, right click on file name in File Explorers plugin. It will show some options along with option to Run. This Run option is used to run the JS scripts

_images/run_with_mocha_option.png

Click on Run, tests will be executed and result will be shown on Terminal.

_images/run_with_mocha_result.png

Test a contract

Similarly unit tests can be written to test the functionality of a smart contract. An example to test default 1_Storage.sol contract can be as:

const { expect } = require("chai");

describe("Storage", function () {
  it("test initial value", async function () {
    // Make sure contract is compiled and artifacts are generated
    const metadata = JSON.parse(await remix.call('fileManager', 'getFile', 'contracts/artifacts/Storage.json'))
    const signer = (new ethers.providers.Web3Provider(web3Provider)).getSigner()
    let Storage = new ethers.ContractFactory(metadata.abi, metadata.data.bytecode.object, signer);
    let storage = await Storage.deploy();
    console.log('storage contract Address: ' + storage.address);
    await storage.deployed()
    expect((await storage.retrieve()).toNumber()).to.equal(0);
  });

  it("test updating and retrieving updated value", async function () {
    const metadata = JSON.parse(await remix.call('fileManager', 'getFile', 'contracts/artifacts/Storage.json'))
    const signer = (new ethers.providers.Web3Provider(web3Provider)).getSigner()
    let Storage = new ethers.ContractFactory(metadata.abi, metadata.data.bytecode.object, signer);
    let storage = await Storage.deploy();
    await storage.deployed()
    const setValue = await storage.store(56);
    await setValue.wait();
    expect((await storage.retrieve()).toNumber()).to.equal(56);
  });

  it("fail test updating and retrieving updated value", async function () {
    const metadata = JSON.parse(await remix.call('fileManager', 'getFile', 'contracts/artifacts/Storage.json'))
    const signer = (new ethers.providers.Web3Provider(web3Provider)).getSigner()
    let Storage = new ethers.ContractFactory(metadata.abi, metadata.data.bytecode.object, signer);
    let storage = await Storage.deploy();
    await storage.deployed()
    const setValue = await storage.store(56);
    await setValue.wait();
    expect((await storage.retrieve()).toNumber()).to.equal(55);
  });
});

Result will be as:

_images/run_with_mocha_storage_test.png

Debugging a test transaction

To debug a transaction in one of the tests, print the transaction hash and input that in the Remix Debugger plugin.

_images/run_with_mocha_print_hash.png

Hardhat-ethers support

Remix also supports methods of hardhat-ethers plugin of Hardhat framework. Available methods under this plugin are:

interface Libraries {
  [libraryName: string]: string;
}

interface FactoryOptions {
  signer?: ethers.Signer;
  libraries?: Libraries;
}

function getContractFactory(name: string, signer?: ethers.Signer): Promise<ethers.ContractFactory>;

function getContractFactory(name: string, factoryOptions: FactoryOptions): Promise<ethers.ContractFactory>;

function getContractFactory(abi: any[], bytecode: ethers.utils.BytesLike, signer?: ethers.Signer): Promise<ethers.ContractFactory>;

function getContractAt(name: string, address: string, signer?: ethers.Signer): Promise<ethers.Contract>;

function getContractAt(abi: any[], address: string, signer?: ethers.Signer): Promise<ethers.Contract>;

function getSigners() => Promise<ethers.Signer[]>;

function getSigner(address: string) => Promise<ethers.Signer>;

function getContractFactoryFromArtifact(artifact: Artifact, signer?: ethers.Signer): Promise<ethers.ContractFactory>;

function getContractFactoryFromArtifact(artifact: Artifact, factoryOptions: FactoryOptions): Promise<ethers.ContractFactory>;

function getContractAtFromArtifact(artifact: Artifact, address: string, signer?: ethers.Signer): Promise<ethers.Contract>;

With this, one can run the tests for a hardhat project easily using Remix.

Example to test Storage contract with this plugin methods can be as:

const { expect } = require("chai");
const { ethers } = require("hardhat");

describe("Storage", function () {
  it("test initial value", async function () {
    const Storage = await ethers.getContractFactory("Storage");
    const storage = await Storage.deploy();
    await storage.deployed();
    console.log('storage deployed at:'+ storage.address)
    expect((await storage.retrieve()).toNumber()).to.equal(0);
  });
   it("test updating and retrieving updated value", async function () {
    const Storage = await ethers.getContractFactory("Storage");
    const storage = await Storage.deploy();
    await storage.deployed();
    const storage2 = await ethers.getContractAt("Storage", storage.address);
    const setValue = await storage2.store(56);
    await setValue.wait();
    expect((await storage2.retrieve()).toNumber()).to.equal(56);
  });
});

Result will be as:

_images/run_with_mocha_hhethers.png