NestJS Enterprise Backend APIs · 课时

智能合约单元测试

学习为您的 Solidity 合约编写全面的单元测试，确保其正确性、安全性和预期行为

智能合约单元测试 是 CoddyKit 上的免费 NestJS Enterprise Backend APIs 课时。这是第 4 节课，共 6 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 NestJS Enterprise Backend APIs 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 NestJS Enterprise Backend APIs 课程共包含 6 节课。

本课时的部分内容尚未翻译，以英文显示。

Unit Testing Smart Contracts

Welcome to unit testing for smart contracts! This lesson will guide you through writing effective tests for your Solidity code.

Unit tests are crucial in traditional software development, but they are absolutely vital in the blockchain world due to the immutable nature of smart contracts and the financial value they often secure.

Why Test Smart Contracts?

Unlike regular applications, smart contracts, once deployed, cannot be easily changed. Bugs can lead to significant financial losses or system failures.

Immutability: Deployed contracts are permanent.
High Stakes: Often manage valuable assets.
Security: Protect against vulnerabilities.
Reliability: Ensure functions behave as expected.
Gas Costs: Bugs can waste user funds.

Thorough testing helps catch issues before deployment.

Introducing Hardhat for Testing

Hardhat is a popular Ethereum development environment that includes a powerful testing framework. It provides a local Ethereum network (Hardhat Network) for fast, isolated testing.

Local Network: Deploy and test without real gas fees.
Ethers.js Integration: Interact with contracts using a familiar JavaScript library.
Debugging: Tools for understanding transaction failures.

We'll use Hardhat to write our unit tests.

Basic Contract for Testing

Let's start with a simple Solidity contract that we'll use for our unit tests. This Counter contract allows us to increment, decrement, and get a count.

Copy and save this as contracts/Counter.sol in your Hardhat project.

pragma solidity ^0.8.0;

contract Counter {
  uint public count;

  constructor() {
    count = 0;
  }

  function increment() public {
    count += 1;
  }

  function decrement() public {
    require(count > 0, "Count cannot be negative");
    count -= 1;
  }

  function getCount() public view returns (uint) {
    return count;
  }
}

Setting Up Your Test File

Hardhat expects test files to be in the test/ directory. We'll use Mocha for our test runner and Chai for assertions, both integrated with Hardhat.

describe(): Groups related tests.
it(): Defines an individual test case.
beforeEach(): Runs before each test in a describe block, useful for setup.

Let's create a file named test/Counter.js.

Deploying Your Contract in Tests

Before we can test our contract's functions, we need to deploy it to our local Hardhat network. The beforeEach block is perfect for this, ensuring a fresh deployment for every test.

Try running this test file. It should pass if your contract is correctly set up.

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

describe("Counter", function () {
  let counter; // Declare 'counter' to be accessible in all tests

  beforeEach(async function () {
    const CounterFactory = await ethers.getContractFactory("Counter");
    counter = await CounterFactory.deploy();
    await counter.deployed(); // Wait for deployment to be confirmed
  });

  // A simple test to confirm deployment
  it("Should confirm the contract is deployed", async function () {
    expect(counter.address).to.not.be.null;
  });
});

Testing Initial State

The first thing to test is if our contract's initial state is correct. Our Counter contract's count should start at 0.

We use expect() from Chai to make assertions about our contract's behavior. to.equal() checks for equality.

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

describe("Counter", function () {
  let counter;

  beforeEach(async function () {
    const CounterFactory = await ethers.getContractFactory("Counter");
    counter = await CounterFactory.deploy();
    await counter.deployed();
  });

  it("Should return the initial count of 0", async function () {
    expect(await counter.getCount()).to.equal(0);
  });

  it("Should confirm the contract is deployed", async function () {
    expect(counter.address).to.not.be.null;
  });
});

Testing State Changes (Increment)

Now let's test a function that changes the contract's state. After calling increment(), we expect the count to increase by one.

Remember that state-changing functions need to be awaited because they involve a transaction on the blockchain.

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

describe("Counter", function () {
  let counter;

  beforeEach(async function () {
    const CounterFactory = await ethers.getContractFactory("Counter");
    counter = await CounterFactory.deploy();
    await counter.deployed();
  });

  it("Should return the initial count of 0", async function () {
    expect(await counter.getCount()).to.equal(0);
  });

  it("Should increment the count by 1", async function () {
    await counter.increment();
    expect(await counter.getCount()).to.equal(1);
  });

  it("Should confirm the contract is deployed", async function () {
    expect(counter.address).to.not.be.null;
  });
});

Testing Function Logic (Decrement)

We can also test the decrement() function. For this, we first need to increment the counter to ensure count is greater than zero.

This shows how tests can involve a sequence of operations to reach a desired state before asserting the outcome.

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

describe("Counter", function () {
  let counter;

  beforeEach(async function () {
    const CounterFactory = await ethers.getContractFactory("Counter");
    counter = await CounterFactory.deploy();
    await counter.deployed();
  });

  it("Should return the initial count of 0", async function () {
    expect(await counter.getCount()).to.equal(0);
  });

  it("Should increment the count by 1", async function () {
    await counter.increment();
    expect(await counter.getCount()).to.equal(1);
  });

  it("Should decrement the count by 1", async function () {
    await counter.increment(); // First increment to make count > 0
    await counter.decrement();
    expect(await counter.getCount()).to.equal(0);
  });

  it("Should confirm the contract is deployed", async function () {
    expect(counter.address).to.not.be.null;
  });
});

Testing for Expected Reverts

Smart contracts often use require() or revert() to enforce conditions. It's vital to test that these conditions correctly trigger a revert when violated.

Chai's to.be.revertedWith() assertion allows us to check for specific error messages.

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

describe("Counter", function () {
  let counter;

  beforeEach(async function () {
    const CounterFactory = await ethers.getContractFactory("Counter");
    counter = await CounterFactory.deploy();
    await counter.deployed();
  });

  it("Should return the initial count of 0", async function () {
    expect(await counter.getCount()).to.equal(0);
  });

  it("Should increment the count by 1", async function () {
    await counter.increment();
    expect(await counter.getCount()).to.equal(1);
  });

  it("Should decrement the count by 1", async function () {
    await counter.increment();
    await counter.decrement();
    expect(await counter.getCount()).to.equal(0);
  });

  it("Should revert if decrementing from zero", async function () {
    await expect(counter.decrement()).to.be.revertedWith("Count cannot be negative");
  });

  it("Should confirm the contract is deployed", async function () {
    expect(counter.address).to.not.be.null;
  });
});

Quick Check: Test Assertions

What are the key benefits of using expect().to.be.revertedWith("...") in smart contract unit tests?

Recap: Unit Testing Power

In this lesson, you've learned the critical importance of unit testing for smart contracts and how to write effective tests using Hardhat, Mocha, and Chai.

Smart contracts require rigorous testing due to their immutability.
Hardhat provides a powerful local environment for fast testing.
You can test initial states, state changes, function logic, and expected reverts.

Mastering unit testing is a fundamental skill for any secure and reliable DApp developer.

常见问题解答

「智能合约单元测试」课时是免费的吗？

是的 — 「智能合约单元测试」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 NestJS Enterprise Backend APIs 课程的其余内容，请升级到 CoddyKit PRO。 NestJS Enterprise Backend APIs 课程共包含 6 节课。

「智能合约单元测试」这节课中我会学到什么？

学习为您的 Solidity 合约编写全面的单元测试，确保其正确性、安全性和预期行为你通过在浏览器中直接运行的动手代码来练习 NestJS Enterprise Backend APIs，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 NestJS Enterprise Backend APIs 需要有经验吗？

无需任何先前经验。CoddyKit 上的 NestJS Enterprise Backend APIs 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 4 节课，共 6 节。

「智能合约单元测试」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 NestJS Enterprise Backend APIs 课中编写并运行代码吗？

能。每节 NestJS Enterprise Backend APIs 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

← 返回 NestJS Enterprise Backend APIs