用松露直接测试以太坊事件

Posted 2023-02-18

【中文标题】用松露直接测试以太坊事件

【英文标题】：Testing ethereum events directly in solidity with truffle

【发布时间】：2017-11-03 03:08:52

【问题描述】：

我发现以下问题用于使用 javascript 测试松露中的事件记录：

Test ethereum Event Logs with truffle

但是 truffle 也支持直接在 solidity 中编写测试。但是，我找不到任何有关如何可靠地测试事件记录的文档。有人可以帮我解决这个问题吗？

【问题讨论】：

你可以在测试中使用 Web3。

【参考方案1】：

考虑使用 OpenZeppelin 测试助手expectEvent。

以构建过程中发出的事件为例：

合同：

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.3;

contract Test 
    address public owner;

    event ContractCreated();

    constructor() 
        owner = msg.sender;

        emit ContractCreated();
    

松露测试：

const  expectEvent  = require('@openzeppelin/test-helpers');

const TestContract = artifacts.require('Test');

contract('Test', function (accounts) 
    const [owner] = accounts;
    const txParams =  from: owner ;

    beforeEach(async function () 
        this.testContract = await TestContract.new(txParams);
    );

    describe('construction', function () 
        it('initial state', async function () 
            expect(await this.testContract.owner()).to.equal(owner);

            await expectEvent.inConstruction(this.testContract, 'ContractCreated');
        );
    );
);

---

package.json

..
  "devDependencies": 
    "@openzeppelin/test-helpers": "^0.5.10"
  
..

【参考方案2】：

一般说明：

请注意，智能合约无法访问事件。根据设计，事件只能从智能合约外部访问。它们不直接存储在区块链中。这意味着您将无法以纯粹的可靠性进行测试。

无法从合约中访问日志及其事件数据（甚至无法从创建它们的合约中访问）。 来源：https://solidity.readthedocs.io/en/v0.5.3/contracts.html#events

使用松露测试事件有效，只需按照以下步骤操作：

1) 创建发出事件的简单合约（contracts/EventEmitter.sol）：

    pragma solidity 0.5.12;

    contract EventEmitter 

    // ---- EVENTS -----------------------------------------------------------------------------------------------------
    event ConstructorDone(address owner, string message);
    event Counter(uint64 count);

    // ---- FIELDS -----------------------------------------------------------------------------------------------------
    uint64 private _count = 0;
    string constant _message = '0x0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789';

    // ---- CONSTRUCTOR ------------------------------------------------------------------------------------------------
    constructor() public 
        emit ConstructorDone(msg.sender, _message);
    

    // ---- STATISTICS FUNCTIONS ---------------------------------------------------------------------------------------
    function getCount() public view returns (uint count) 
        return _count;
    

    // ---- CORE FUNCTIONS ---------------------------------------------------------------------------------------------
    function increment() public 
        _count++;
        emit Counter(_count);
    

2) 创建测试合约（test/TestAnEventEmitter.sol）：

pragma solidity 0.5.12;

import "truffle/Assert.sol";
import "../contracts/EventEmitter.sol";

contract TestAnEventEmitter 

    EventEmitter private eventEmitter;

    uint eContracts = 0;

    address private owner;

    function assertCount() private 
        Assert.equal(eventEmitter.getCount(), eContracts, "Unexpected count of created contracts");
    

    constructor() public
        eventEmitter = new EventEmitter();
        owner = address(this);
    

3) 创建测试代码 (test/TestAnEventEmitter.js)：

const EventEmitter = artifacts.require("EventEmitter");
const truffleAssert = require('truffle-assertions');

/** Expected number of counter */
var eCount = 0;

/** The Contract's instance */
var eventEmitter;

global.CONTRACT_ADDRESS = '';

async function assertContractCount() 
    assert.equal(await eventEmitter.getCount.call(), eCount, "Wrong number of created contracts");


contract('EventEmitter', async () => 

    before(async () => 
        eventEmitter = await EventEmitter.new();
    );

    describe("1.1 Basic", function () 

        it("1.1.1 has been created", async () => 
            global.CONTRACT_ADDRESS = eventEmitter.address;
            console.log('        contract => ' + global.CONTRACT_ADDRESS);
            await assertContractCount();
        );

        it("1.1.2 should emit ConstructorDone event", async () => 
            // Get the hash of the deployment transaction
            let txHash = eventEmitter.transactionHash;

            // Get the transaction result using truffleAssert
            let result = await truffleAssert.createTransactionResult(eventEmitter, txHash);

            // Check event
            truffleAssert.eventEmitted(result, 'ConstructorDone', (ev) => 
                console.log('        owner => ' + ev.owner);
                return true;
            );
        );
    );

    describe("1.2 Check calls of increment()", function () 

        it("1.2.1 first call should increase the counts correctly", async () => 
            // Pre-Conditions
            await assertContractCount();

            // Creation
            let tx = await eventEmitter.increment();
            eCount++;

            // Expected Event
            truffleAssert.eventEmitted(tx, 'Counter', (ev) => 
                return parseInt(ev.count) === eCount;
            );

            // Post-Conditions
            await assertContractCount();
        );

        it("1.2.2 second call should increase the counts correctly", async () => 
            // Pre-Conditions
            await assertContractCount();

            // Creation
            let tx = await eventEmitter.increment();
            eCount++;

            // Expected Event
            truffleAssert.eventEmitted(tx, 'Counter', (ev) => 
                return parseInt(ev.count) === eCount;
            );

            // Post-Conditions
            await assertContractCount();
        );

        it("1.2.3 third call should increase the counts correctly", async () => 
            // Pre-Conditions
            await assertContractCount();

            // Creation
            let tx = await eventEmitter.increment();
            eCount++;

            // Expected Event
            truffleAssert.eventEmitted(tx, 'Counter', (ev) => 
                return parseInt(ev.count) === eCount;
            );

            // Post-Conditions
            await assertContractCount();
        );
    );
);

4) 运行测试：

$ truffle test
Using network 'development'.


Compiling your contracts...
===========================
> Compiling ./test/TestAnEventEmitter.sol



  Contract: EventEmitter
    1.1 Basic
        contract => 0xeD62E72c2d04Aa385ec764c743219a93ae49e796
      ✓ 1.1.1 has been created (56ms)
        owner => 0xbD004d9048C9b9e5C4B5109c68dd569A65c47CF9
      ✓ 1.1.2 should emit ConstructorDone event (63ms)
    1.2 Check calls of increment()
      ✓ 1.2.1 first call should increase the counts correctly (142ms)
      ✓ 1.2.2 second call should increase the counts correctly (160ms)
      ✓ 1.2.3 third call should increase the counts correctly (156ms)

完整来源（带有 package.json 等）： https://github.com/MarkusSprunck/ethereum-event-scan

有关事件和监控的更多信息： https://www.sw-engineering-candies.com/blog-1/Ethereum-Event-Explorer-for-Smart-Contracts

（免责声明：我是这个项目和博客的作者）

【参考方案3】：

事件是存储在区块链中的日志。要获得事件，您需要观看链。 http://solidity.readthedocs.io/en/develop/contracts.html#events

Solidity Truffle 测试是合同。而合约只是存储代码的以太坊账户。当该帐户收到交易时，该代码将被执行。以太坊合约无法通过观察链获取事件日志。所以 Solidity 不支持获取事件。 https://github.com/ethereum/wiki/wiki/White-Paper#ethereum-accounts