Implementation:Webdriverio Webdriverio XPath PageSource

Knowledge Sources	Webdriverio_Webdriverio
Domains	Mobile_Testing, Selector_Validation
Last Updated	2026-02-12 00:00 GMT

Overview

The XPath PageSource module validates selector uniqueness by counting matching elements in the page source XML using regex-based parsing.

Description

This module provides three exported functions for selector uniqueness validation. isSelectorUniqueInPageSource is the main entry point that dispatches to strategy-specific checks based on selector prefix: accessibility ID selectors (~) check both name and label attributes for uniqueness, predicate string selectors are counted via countMatchingElementsByPredicate, and class chain selectors via countMatchingElementsByClassChain. Both counting functions parse predicate conditions from selector strings and match them against element attributes in the page source XML using regex patterns. The module avoids full DOM parsing by using targeted regex matching for performance.

Usage

These functions are called by the selector builder module to verify that a proposed native selector uniquely identifies a single element before recommending it as a replacement.

Code Reference

Source Location

Repository: Webdriverio_Webdriverio
File: packages/wdio-appium-service/src/mobileSelectorPerformanceOptimizer/utils/xpath-page-source.ts
Lines: 18-155

Signature

export function isSelectorUniqueInPageSource(selector: string, pageSource: string): boolean

export function countMatchingElementsByPredicate(predicateString: string, pageSource: string): number

export function countMatchingElementsByClassChain(chainString: string, pageSource: string): number

Import

import { isSelectorUniqueInPageSource, countMatchingElementsByPredicate, countMatchingElementsByClassChain } from './utils/xpath-page-source.js'

I/O Contract

Inputs

Name	Type	Required	Description
selector	`string`	Yes	Full selector string with strategy prefix (e.g., `~Login`, `-ios predicate string:...`, `-ios class chain:...`)
pageSource	`string`	Yes	Raw XML page source string to search within
predicateString	`string`	Yes	iOS predicate string without prefix (for countMatchingElementsByPredicate)
chainString	`string`	Yes	iOS class chain string without prefix (for countMatchingElementsByClassChain)

Outputs

Name	Type	Description
isSelectorUniqueInPageSource return	`boolean`	True if exactly one element matches the selector in the page source
countMatchingElementsByPredicate return	`number`	Count of elements matching the predicate conditions
countMatchingElementsByClassChain return	`number`	Count of elements matching the class chain pattern

Usage Examples

Checking Selector Uniqueness

import { isSelectorUniqueInPageSource } from './xpath-page-source.js'

const pageSource = `
<AppiumAUT>
  <XCUIElementTypeButton name="Login" label="Login" />
  <XCUIElementTypeButton name="Cancel" label="Cancel" />
</AppiumAUT>`

isSelectorUniqueInPageSource('~Login', pageSource)
// true (only one element has name="Login")

isSelectorUniqueInPageSource('~Cancel', pageSource)
// true

isSelectorUniqueInPageSource(
    "-ios predicate string:type == 'XCUIElementTypeButton'",
    pageSource
)
// false (two buttons exist)

Counting Predicate Matches

import { countMatchingElementsByPredicate } from './xpath-page-source.js'

const count = countMatchingElementsByPredicate(
    "type == 'XCUIElementTypeButton' AND name == 'Login'",
    pageSource
)
// 1

Related Pages

Page Connections

Double-click a node to navigate. Hold to expand connections.

Principle

Implementation

Heuristic

Environment