Reproduce a Flaky Failure

Use this loop when a test fails only sometimes:

1. Log the chaos seed only on failure.
2. Put that seed into the config.
3. Re-run the same user actions.
4. Assert the log shape so the replay proves the same chaos path.

Playwright

import { test, expect } from '@playwright/test';
import {
  formatSeedReproduction,
  getChaosLog,
  getChaosSeed,
  injectChaos,
} from '@chaos-maker/playwright';

test.afterEach(async ({ page }, testInfo) => {
  if (testInfo.status !== testInfo.expectedStatus) {
    console.error(formatSeedReproduction(await getChaosSeed(page)));
  }
});

test('replays checkout failure', async ({ page }) => {
  await injectChaos(page, {
    seed: 1234,
    network: {
      failures: [{ urlPattern: '/api/payments', statusCode: 503, probability: 0.3 }],
    },
  });

  await page.goto('/checkout');
  await page.click('#pay-now');
  await expect(page.locator('[data-testid="payment-error"]')).toBeVisible();

  const log = await getChaosLog(page);
  expect(log.some((event) => event.type === 'network:failure' && event.applied)).toBe(true);
});

Cypress

import { formatSeedReproduction } from '@chaos-maker/cypress';

afterEach(function () {
  if (this.currentTest?.state === 'failed') {
    cy.getChaosSeed().then((seed) => {
      console.error(formatSeedReproduction(seed));
    });
  }
});

it('replays checkout failure', () => {
  cy.injectChaos({
    seed: 1234,
    network: {
      failures: [{ urlPattern: '/api/payments', statusCode: 503, probability: 0.3 }],
    },
  });

  cy.visit('/checkout');
  cy.get('#pay-now').click();
  cy.get('[data-testid="payment-error"]').should('be.visible');
  cy.getChaosLog().should((log) => {
    expect(log.some((event) => event.type === 'network:failure' && event.applied)).to.equal(true);
  });
});

WebdriverIO

import { browser, expect, $ } from '@wdio/globals';
import {
  formatSeedReproduction,
  getChaosLog,
  getChaosSeed,
  injectChaos,
} from '@chaos-maker/webdriverio';

afterEach(async function () {
  if (this.currentTest?.state === 'failed') {
    console.error(formatSeedReproduction(await getChaosSeed(browser)));
  }
});

it('replays checkout failure', async () => {
  await browser.url('/checkout');
  await injectChaos(browser, {
    seed: 1234,
    network: {
      failures: [{ urlPattern: '/api/payments', statusCode: 503, probability: 0.3 }],
    },
  });

  await $('#pay-now').click();
  await expect($('[data-testid="payment-error"]')).toBeDisplayed();

  const log = await getChaosLog(browser);
  expect(log.some((event) => event.type === 'network:failure' && event.applied)).toBe(true);
});

Puppeteer

import {
  formatSeedReproduction,
  getChaosLog,
  getChaosSeed,
  injectChaos,
} from '@chaos-maker/puppeteer';

try {
  await injectChaos(page, {
    seed: 1234,
    network: {
      failures: [{ urlPattern: '/api/payments', statusCode: 503, probability: 0.3 }],
    },
  });

  await page.goto('http://localhost:3000/checkout');
  await page.click('#pay-now');
  await page.waitForSelector('[data-testid="payment-error"]');

  const log = await getChaosLog(page);
  if (!log.some((event) => event.type === 'network:failure' && event.applied)) {
    throw new Error('Expected payment failure chaos');
  }
} catch (error) {
  console.error(formatSeedReproduction(await getChaosSeed(page)));
  throw error;
}