Ethereum event fixtures for js.

custom.fixture.js

/**
 * Fixture for a custom ethereum event with unique return values
 */
import {
  random, finance, date, lorem,
} from 'faker';
import generateEvent from './event.fixture';
import { fromDecimal, fromDate } from 'dapp-utils';

const EVENT_NAME = 'TransferComplete';

/**
 * Generate a fake TransferComplete event object.
 *
 * @param {object} [overrides] - Fields to override the generated default event values.
 * @return {object} - TransferComplete event object.
 */
const generateCustomEvent = (overrides = {}) => {
  // example return values you might have
  const returnValue1 = finance.ethereumAddress();
  const returnValue2 = fromDecimal(random.float(), 10);
  const timestamp = fromDate(date.past());

  // merge in the following order:
  //  1. generic fields all events share
  //  2. unique to your custom event (mainly return values and `event` name)
  //  3. provided overrides (allowing us to test expected values)
  return {
    ...generateEvent(),
    event: EVENT_NAME,
    returnValues: {
      0: returnValue1,
      1: returnValue2,
      2: timestamp,
      returnValue1,
      returnValue2,
      timestamp,
    },
    ...overrides,
  };
};

export default generateCustomEvent;

Ethereum event fixtures for js.md

To install a relatively recent version of Faker you'll need to install from a commit. The maintainer is still active and merging new features, but does not cut new releases.

npm install --save-dev faker@Marak/faker.js#<commit-sha>

I.e. npm install --save-dev faker@Marak/faker.js#d3ce6f1 (latest commit at the time of writing).

event.fixture.js

import { random, finance } from 'faker';

/**
 * Mock an ethereum event object, minus return values unique to specific event types.
 */
const generateEvent = () => ({
  address: finance.ethereumAddress(),
  blockNumber: random.number(20000),
  transactionHash: random.hexaDecimal(64),
  transactionIndex: 0,
  blockHash: random.hexaDecimal(64),
  logIndex: 0,
  removed: random.boolean(),
  id: `log_${random.hexaDecimal(8)}`,
  signature: random.hexaDecimal(64),
  raw: {
    data: random.hexaDecimal(1000),
    topics: [random.hexaDecimal(64)],
  },
});

export default generateEvent;

example.test.js

import generateCustomEvent from './fixtures/custom.fixture.js';

describe('CustomEvent', () => {
  it('should ...', () => {
    const event = generateCustomEvent();
    
    // ...
  });

  it('should ...', () => {
    const event = generateCustomEvent({
      returnValues: {
        returnValue1: 'foo bar',
      },
    });
    
    // ...
  });
});