Implementation:Teamcapybara Capybara Capybara Modify Selector

Knowledge Sources	Capybara
Domains	Testing, Selector_System
Last Updated	2026-02-12 00:00 GMT

Overview

Concrete tool for modifying existing selector definitions provided by Capybara.modify_selector.

Description

Capybara.modify_selector(name, &block) delegates to Capybara::Selector.update(name, &block). This looks up the existing Selector::Definition by name and calls instance_eval(&block) on it, allowing new filters, labels, or expression modifications to be added to the existing definition.

Usage

Call in test configuration to extend built-in selectors with application-specific filters.

Code Reference

Source Location

• Repository: capybara
• File: lib/capybara.rb (L200-202), lib/capybara/selector/selector.rb (L18-19)

Signature

def modify_selector(name, &block)
  # @param name [Symbol] Name of existing selector to modify
  # @yield Block evaluated in context of the existing Selector::Definition
  Capybara::Selector.update(name, &block)
end

Import

require 'capybara'

I/O Contract

Inputs

Name	Type	Required	Description
name	Symbol	Yes	Name of existing selector to modify
block	Block	Yes	Definition DSL block to apply to existing selector

Outputs

Name	Type	Description
updated definition	Selector::Definition	Existing definition updated with new filters/behavior

Usage Examples

Add Filter to Built-In Selector

Capybara.modify_selector(:button) do
  node_filter(:btn_style, valid_values: [:primary, :secondary, :danger]) do |node, style|
    node[:class].split.include?("btn-#{style}")
  end
end

# Now works:
find(:button, 'Submit', btn_style: :primary)
click_button 'Delete', btn_style: :danger

Extend Field Selector

Capybara.modify_selector(:field) do
  node_filter(:required, :boolean) do |node, value|
    node[:required] == value.to_s || (value && node.has_attribute?('required'))
  end
end

find(:field, 'Email', required: true)

Related Pages

Implements Principle

• Principle:Teamcapybara_Capybara_Selector_Modification