Implementation:SeleniumHQ Selenium Closure Asserts

Knowledge Sources	SeleniumHQ_Selenium Google Closure Library
Domains	JavaScript_Atoms, Vendored_Library
Last Updated	2026-02-12 00:00 GMT

Overview

Vendored Google Closure Library module providing runtime assertion utilities used by Selenium JavaScript atoms.

Description

goog.asserts is a vendored copy of the Google Closure Library module. It provides utilities to check preconditions, postconditions, and invariants at runtime. The Closure Compiler gives these methods special treatment for type-inference, allowing assertions like `goog.asserts.assert(foo)` to narrow types. The compiler can optionally strip asserts from production builds. Selenium uses this as part of its JavaScript atom infrastructure for browser automation commands.

Usage

This module is consumed internally by Selenium's JavaScript atoms build system. It is not imported directly by end users.

Code Reference

Source Location

• Repository: SeleniumHQ_Selenium
• File: third_party/closure/goog/asserts/asserts.js
• Lines: 1-451

Key Exports

goog.module('goog.asserts');

exports.ENABLE_ASSERTS
exports.AssertionError(messagePattern, messageArgs)
exports.setErrorHandler(errorHandler)
exports.assert(condition, opt_message, var_args)
exports.assertExists(value, opt_message, var_args)
exports.fail(opt_message, var_args)
exports.assertNumber(value, opt_message, var_args)
exports.assertString(value, opt_message, var_args)
exports.assertFunction(value, opt_message, var_args)
exports.assertObject(value, opt_message, var_args)
exports.assertArray(value, opt_message, var_args)
exports.assertBoolean(value, opt_message, var_args)
exports.assertElement(value, opt_message, var_args)
exports.assertInstanceof(value, type, opt_message, var_args)
exports.assertFinite(value, opt_message, var_args)

Related Pages

• Environment:SeleniumHQ_Selenium_Contributor_Development_Environment