Implementation:Nightwatchjs Nightwatch Assertion Type Definitions

Knowledge Sources	Nightwatchjs_Nightwatch Nightwatch Assertions
Domains	Testing, Type_System, Assertions
Last Updated	2026-02-12 00:00 GMT

Overview

TypeScript type definitions for Nightwatch's built-in assertion API, including element assertions, page assertions, and Node.js assert wrappers.

Description

The assertions.d.ts file defines the complete TypeScript interface for Nightwatch's `browser.assert` and `browser.verify` namespaces. It includes:

NightwatchCommonAssertions — Element-level assertions like `attributeContains`, `textEquals`, `visible`, `elementPresent`, `cssProperty`, `urlEquals`, `titleEquals`, and more.
NightwatchNodeAssertions — Node.js `assert` module wrappers (`equal`, `deepEqual`, `strictEqual`, `throws`, `rejects`, etc.) integrated into the Nightwatch chain.
NightwatchAssertions — Combined interface with `.not` negation support.
Assert — The top-level type combining both common and Node assertions.

All assertion methods return `Awaitable` types, enabling both callback and async/await usage patterns.

⚠️ Deprecation Warning: This file contains 7 deprecated assertion methods (`elementNotPresent`, `cssClassNotPresent`, `cssClassPresent`, `containsText`, `title`, `value`, `hidden`) that have been superseded by modern equivalents. See Heuristic:Nightwatchjs_Nightwatch_Warning_Deprecated_API_Members for migration guidance.

Usage

These type definitions are consumed automatically when writing Nightwatch tests in TypeScript. They provide autocompletion and type checking for `browser.assert.*` and `browser.verify.*` calls.

Code Reference

Source Location

Repository: Nightwatchjs_Nightwatch
File: types/assertions.d.ts
Lines: 1-672

Signature

export interface NightwatchCommonAssertions<ReturnType> {
  attributeContains(selector: Definition, attribute: string, expected: string, message?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<string>>;
  attributeEquals(selector: Definition, attribute: string, expected: string, message?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<string>>;
  textContains(selector: Definition, expectedText: string, msg?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<string>>;
  textEquals(selector: Definition, expectedText: string, msg?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<string>>;
  visible(selector: Definition, message?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<boolean>>;
  elementPresent(selector: ScopedSelector, msg?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<ElementResult[]>>;
  urlEquals(expected: string, message?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<string>>;
  titleEquals(expected: string, message?: string): Awaitable<IfUnknown<ReturnType, this>, NightwatchAssertionsResult<string>>;
  // ... 30+ additional assertion methods
}

export interface NightwatchAssertions<ReturnType> extends NightwatchCommonAssertions<ReturnType>, NightwatchCustomAssertions<ReturnType> {
  not: Omit<NightwatchAssertions<ReturnType>, 'not'>;
}

export interface Assert<ReturnType = unknown> extends NightwatchAssertions<ReturnType>, NightwatchNodeAssertions<ReturnType> {}

Import

import { Assert, NightwatchAssertions, NightwatchCommonAssertions } from 'nightwatch';

I/O Contract

Inputs

Name	Type	Required	Description
selector	Definition / ScopedSelector	Yes (for element assertions)	CSS selector, XPath, or element reference
expected	string / number / RegExp	Yes	Expected value to assert against
message	string	No	Custom assertion failure message

Outputs

Name	Type	Description
NightwatchAssertionsResult	Object	Contains `value`, `status: 0`, `returned: 1`, `passed: true`
NightwatchNodeAssertionsResult	Object	Contains `value: null`, `returned: 1`

Usage Examples

Element Assertions

// Using browser.assert in a Nightwatch test
describe('Assertion examples', function() {
  it('demonstrates assertion types', async function(browser) {
    await browser.assert.visible('#main');
    await browser.assert.textContains('#heading', 'Welcome');
    await browser.assert.attributeEquals('body', 'class', 'loaded');
    await browser.assert.elementPresent('.content');
    await browser.assert.urlContains('/dashboard');
    await browser.assert.titleEquals('My App');

    // Negated assertions
    await browser.assert.not.visible('.hidden-element');
    await browser.assert.not.elementPresent('.removed');
  });
});

Node.js Assert Wrappers

describe('Node assert wrappers', function() {
  it('uses Node.js assert methods', async function(browser) {
    await browser.assert.ok(true, 'Value is truthy');
    await browser.assert.equal(1 + 1, 2, 'Math works');
    await browser.assert.strictEqual('hello', 'hello');
    await browser.assert.deepEqual({ a: 1 }, { a: 1 });
  });
});

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