Assertions

unibrowser provides built-in expect* methods on pages and elements, plus standalone assertion functions.

Page Assertions

// Title
await page.expectTitle("My App");
await page.expectTitle(/My App/);
await page.expectTitleContains("Dashboard");

// URL
await page.expectURL("https://example.com/dashboard");
await page.expectURL(/\/dashboard/);
await page.expectURLContains("dashboard");

Element Assertions

const el = page.locator("h1");

// Visibility
await el.expectVisible();
await el.expectHidden();

// Text
await el.expectText("Welcome");
await el.expectTextContains("Welcome");

// State
await el.expectEnabled();
await el.expectDisabled();
await el.expectChecked();

// Attributes
await el.expectAttribute("href", "/dashboard");

All element assertions wait for the element to reach the expected state first.

Standalone Assertions

Import from unibrowser for custom logic:

import {
  assert, assertEqual, assertNotEqual,
  assertContains, assertMatch,
  assertTrue, assertFalse,
  assertGreaterThan, assertLessThan,
  assertLength, assertThrows,
} from "unibrowser";

assert(condition, message)

Base assertion. Throws AssertionError if condition is falsy.

assert(items.length > 0, "Expected at least one item");

assertEqual(actual, expected, message?)

Strict === equality.

assertEqual(response.status, 200);
assertEqual(user.name, "Alice", "Username mismatch");

assertNotEqual(actual, expected, message?)

Strict !== inequality.

assertContains(haystack, needle, message?)

String contains.

assertContains(page.url(), "/dashboard");
assertContains(html, "Welcome back");

assertMatch(value, pattern, message?)

RegExp match.

assertMatch(title, /^Dashboard/);

assertTrue(value, message?) / assertFalse(value, message?)

Boolean assertions.

assertTrue(isVisible);
assertFalse(isLoading);

assertGreaterThan(actual, expected, message?) / assertLessThan(actual, expected, message?)

Numeric comparisons.

assertGreaterThan(count, 0);
assertLessThan(responseTime, 5000);

assertLength(value, expected, message?)

Array/string length.

assertLength(items, 5);
assertLength("hello", 5);

assertThrows(fn, expectedError?, message?)

Assert function throws.

assertThrows(() => JSON.parse("invalid"));

assertThrows(
  () => parseConfig("bad"),
  "Invalid config"
);

assertThrows(
  () => riskyOperation(),
  /error code \d+/
);

AssertionError

All assertions throw AssertionError on failure.

import { AssertionError } from "unibrowser";

try {
  await page.expectTitle("Wrong Title");
} catch (e) {
  if (e instanceof AssertionError) {
    console.log(e.actual);   // "Example Domain"
    console.log(e.expected); // "Wrong Title"
  }
}

Custom Messages

Every assertion accepts an optional message parameter:

await page.expectTitle("Home", "Homepage should have title 'Home'");
await el.expectVisible("Submit button should be visible");
assertEqual(status, 200, "API should return 200 OK");