### What are Web-First Assertions?
Web-first assertions continuously poll the element until the expected state is reached:
```typescript
// ✅ Web-first assertion (waits up to 5s for the banner to appear)
await expect(page.getByText('Login successful')).toBeVisible();
// Checks exact or regex text content
await expect(page.locator('.welcome-msg')).toHaveText(/Welcome, Alex/);
// Asserts input field value
await expect(page.getByLabel('Username')).toHaveValue('alex99');
```
### Common Assertions Cheatsheet:
- `expect(locator).toBeVisible()`
- `expect(locator).toBeHidden()`
- `expect(locator).toBeEnabled()`
- `expect(locator).toBeChecked()`
- `expect(locator).toHaveCount(expectedCount)`