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】：
标签： unit-testing events ethereum solidity smartcontracts
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"
}
..
}
【讨论】：
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）
【讨论】：
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
【讨论】：