Debugging Failures

Tools for finding out what happened

Playwright: the trace viewer records each action with DOM snapshots, console logs, network requests and source; enable it with trace: 'on-first-retry' (or 'retain-on-failure') and open it with npx playwright show-trace or from the HTML report. UI mode (--ui) offers watch mode and a time-travel view locally; --debug opens the inspector to step through actions; screenshot and video options capture failures. Cypress: the interactive runner keeps a command log with time-travel snapshots for every command, and you can use the browser DevTools directly because tests run in the browser; cy.pause() and .debug() stop execution. In cypress run, screenshots are taken on failure automatically, and video recording is configurable (off by default in recent versions; check the docs for your version).

Debugging switches

Config and CLI for both tools.

// playwright.config.ts (excerpt)
use: {
  trace: 'on-first-retry',
  screenshot: 'only-on-failure',
  video: 'retain-on-failure',
},
// CLI:
//   npx playwright test --ui
//   npx playwright test tests/cart.spec.ts --debug
//   npx playwright show-trace test-results/<test-folder>/trace.zip

// cypress.config.ts (excerpt)
export default defineConfig({
  video: true,                     // record videos in cypress run
  screenshotOnRunFailure: true,
  e2e: { baseUrl: 'http://localhost:3000' },
});
// in a test: cy.get('[data-cy=cart]').debug(); cy.pause();

A flight recorder

A trace is the black box of a test run: when something crashes, you replay every step with what the screen, console and network looked like at that moment.

Read the first failure, not the last

A timeout on the final assertion is often a symptom. Step back through the trace or command log to the first action whose result was not what you expected.

त्वरित जाँच: What does `trace: 'on-first-retry'` do in Playwright?

• Records a trace when a failed test is retried, for later inspection
• Records traces for every passing test
• Retries tests forever
• Disables screenshots