Why Assertions Matter

Let me tell you something that will save your career. A test without assertions is not a test. It is a script. It clicks buttons, fills forms, navigates pages -- and then walks away. It never checks if anything actually worked. This is the most common mistake I see in QA teams.

The Doctor Analogy

Think of it this way. You visit a doctor. The doctor walks in, says hello, sits down, writes a prescription, and leaves. Never checks your blood pressure. Never listens to your heartbeat. Never asks where it hurts. That is a test without assertions. The visit happened. But no diagnosis was made. No one knows if you are healthy or dying.

Now imagine a doctor who checks your BP, listens to your chest, runs a blood test, checks your reflexes. That doctor is writing assertions. Each check verifies one thing. BP is 120/80? Pass. Heart rate is 72? Pass. Blood sugar is 300? FAIL -- something is wrong. That is what assertions do for your tests.

The Playwright Way

Playwright uses the expect() function for all assertions. It comes from @playwright/test -- not from Jest, not from Chai. Playwright built its own assertion library specifically designed for web testing. The magic? Every assertion auto-retries. More on that in the next lesson.

import { test, expect } from '@playwright/test';

test('login should work', async ({ page }) => {
  await page.goto('/banking');
  await page.getByLabel('Username').fill('testuser');
  await page.getByLabel('Password').fill('password123');
  await page.getByRole('button', { name: 'Login' }).click();

  // WITHOUT assertions -- this test always passes. Useless.
  // WITH assertions -- now we actually verify something happened:
  await expect(page).toHaveURL(/\/dashboard/);
  await expect(page.getByText('Welcome, testuser')).toBeVisible();
  await expect(page.getByRole('button', { name: 'Logout' })).toBeVisible();
});