JavaScript testing helpers for Ethereum smart contract development. These are specially suited for truffle 5 (using web3 1.0). chai bn.js assertions using chai-bn are also included.
npm install --save-dev openzeppelin-test-helpers// Import all required modules from openzeppelin-test-helpers
const { BN, constants, expectEvent, shouldFail } = require('openzeppelin-test-helpers');
// Import preferred chai flavor: both expect and should are supported
const { expect } = require('chai');
const ERC20 = artifacts.require('ERC20');
contract('ERC20', ([sender, receiver]) => {
beforeEach(async function () {
this.erc20 = await ERC20.new();
this.value = new BN(1); // The bundled BN library is the same one truffle and web3 use under the hood
});
it('reverts when transferring tokens to the zero address', async function () {
// Edge cases that trigger a require statement can be tested for, optionally checking the revert reason as well
await shouldFail.reverting(this.erc20.transfer(constants.ZERO_ADDRESS, this.value, { from: sender }));
});
it('emits a Transfer event on successful transfers', async function () {
const { logs } = this.erc20.transfer(receiver, this.value, { from: sender });
// Log-checking will not only look at the event name, but also the values, which can be addresses, strings, numbers, etc.
expectEvent.inLogs(logs, 'Transfer', { from: sender, to: receiver, value: this.value });
});
it('updates balances on successful transfers', async function () {
this.erc20.transfer(receiver, this.value, { from: sender });
// chai-bn is installed, which means BN values can be tested and compared using the bignumber property in chai
expect(await this.token.balanceOf(receiver)).to.be.bignumber.equal(this.value);
});
});This documentation is a work in progress: if in doubt, head over to the tests directory to see examples of how each helper can be used.
All returned numbers are of type BN.
Helper to keep track of ether balances of a specific account
Returns the current balance of an account
const balance = await balance.current(account)Returns the current Ether balance of an account.
const balanceTracker = await balance.tracker(account) //instantiation
const accounBalance = await balanceTracker.get() //returns the current balance of accountReturns the change in the Ether since the last check(either get() or delta())
const balanceTracker = await balance.tracker(receiver)
send.ether(sender, receiver, ether('10'))
(await balanceTracker.delta()).should.be.bignumber.equal('10');
(await balanceTracker.delta()).should.be.bignumber.equal('0');Or using get():
const balanceTracker = await balance.tracker(account) //instantiation
const accounBalance = await balanceTracker.get() //returns the current balance of account
(await balanceTracker.delta()).should.be.bignumber.equal('0');A bn.js object. Use new BN(number) to create BN instances.
Converts a value in Ether to wei.
A chai expect instance, containing the bignumber property (via chai-bn).
expect(new BN('2')).to.be.bignumber.equal('2');Asserts logs contains an entry for an event with name eventName, for which all entries in eventArgs match.
Same as inLogs, but for events emitted during the construction of contract.
const contract = await MyContract.new(5);
await expectEvent.inConstruction(contract, 'Created', { value: 5 });Same as inLogs, but for events emitted in an arbitrary transaction (of hash txHash), by an arbitrary contract (emitter), even if it was indirectly called (i.e. if it was called by another smart contract and not an externally owned account).
Calculates the EIP 165 interface ID of a contract, given a series of function signatures.
Sends value Ether from from to to.
Sends a transaction to contract target, calling method name with argValues, which are of type argTypes (as per the method's signature).
A chai should instance, containing the bignumber property (via chai-bn).
Collection of assertions for failures (similar to chai's throw). shouldFail will accept any exception type, but more specific functions exist and their usage is encouraged.
Only accepts failures caused due to an EVM revert (e.g. a failed require).
Like shouldFail.reverting, this helper only accepts failures caused due to an EVM revert (e.g. a failed require). Furthermore, it checks whether revert reason string includes passed message. For example:
contract Owned {
address private _owner;
constructor () {
_owner = msg.sender;
}
function doOwnerOperation() public view {
require(msg.sender == _owner, "Unauthorized");
....
}
}Can be tested as follows:
const { shouldFail } = require('openzeppelin-test-helpers');
const Owned = artifacts.require('Owned');
contract('Owned', ([owner, other]) => {
beforeEach(async function () {
this.owned = Owned.new();
});
describe('doOwnerOperation', function() {
it('Fails when called by a non-owner account', async function () {
await shouldFail.reverting.withMessage(this.owned.doOwnerOperation({ from: other }), "Unauthorized");
});
});
...Use this helper to specify the expected error message, when you're testing a function that can revert for multiple reasons.
Only accepts failures due to a failed assert (which executes an invalid opcode).
Only accepts failures due to the transaction running out of gas.
Returns an instance of an ERC1820Registry deployed as per the specification (i.e. the registry is located at the canonical address). This can be called multiple times to retrieve the same instance.
Forces a block to be mined, incrementing the block height.
Returns the timestamp of the latest mined block. Should be coupled with advanceBlock to retrieve the current blockchain time.
Returns the latest mined block number.
Increases the time of the blockchain by duration (in seconds), and mines a new block with that timestamp.
Same as increase, but a target time is specified instead of a duration.
Helpers to convert different time units to seconds. Available helpers are: seconds, minutes, hours, days, weeks and years.
await time.increase(time.duration.years(2));