Create custom RSpec matcher to validate form group HTML output

The specs that validate what kind of content is generated for all
the supported HTML tag built through the Form Builder have a lot
of repeated code.

This commit tackles that issue by supporting a custom RSpec matcher
that validates the HTML output generated by the Form Builder.

spec/lib/govuk_elements_form_builder/form_builder_spec.rb

@@ -30,89 +30,42 @@ def type_for(method, type)
   end
 
   shared_examples_for 'input field' do |method, type|
-
-    def size(method, size)
-      method == :text_area ? '' : %'size="#{size}" '
-    end
+    let(:default_builder_options) { { resource: 'person' } }
 
     it 'outputs label and input wrapped in div' do
       output = builder.send method, :name
 
-      expect_equal output, [
-        '<div class="form-group">',
-        '<label class="form-label" for="person_name">',
-        'Full name',
-        '</label>',
-        %'<#{element_for(method)} class="form-control" #{type_for(method, type)}name="person[name]" id="person_name" />',
-        '</div>'
-      ]
+      expect(output).to match_form_group(default_builder_options.merge(field: :name, input_type: method))
     end
 
     it 'supports attributes defined as a string' do
-      output = builder.send method, 'name', class: 'custom-class'
+      output = builder.send method, 'name'
 
-      expect_equal output, [
-        '<div class="form-group">',
-        '<label class="form-label" for="person_name">',
-        'Full name',
-        '</label>',
-        %'<#{element_for(method)} class="form-control custom-class" #{type_for(method, type)}name="person[name]" id="person_name" />',
-        '</div>'
-      ]
+      expect(output).to match_form_group(default_builder_options.merge(field: :name, input_type: method))
     end
 
     it 'adds custom class to input when passed class: "custom-class"' do
       output = builder.send method, :name, class: 'custom-class'
 
-      expect_equal output, [
-        '<div class="form-group">',
-        '<label class="form-label" for="person_name">',
-        'Full name',
-        '</label>',
-        %'<#{element_for(method)} class="form-control custom-class" #{type_for(method, type)}name="person[name]" id="person_name" />',
-        '</div>'
-      ]
+      expect(output).to match_form_group(default_builder_options.merge(field: :name, input_type: method, class: 'custom-class'))
     end
 
     it 'adds custom classes to input when passed class: ["custom-class", "another-class"]' do
       output = builder.send method, :name, class: ['custom-class', 'another-class']
 
-      expect_equal output, [
-        '<div class="form-group">',
-        '<label class="form-label" for="person_name">',
-        'Full name',
-        '</label>',
-        %'<#{element_for(method)} class="form-control custom-class another-class" #{type_for(method, type)}name="person[name]" id="person_name" />',
-        '</div>'
-      ]
+      expect(output).to match_form_group(default_builder_options.merge(field: :name, input_type: method, class: 'custom-class another-class'))
     end
 
     it 'passes options passed to text_field onto super text_field implementation' do
       output = builder.send method, :name, size: 100
-      expect_equal output, [
-        '<div class="form-group">',
-        '<label class="form-label" for="person_name">',
-        'Full name',
-        '</label>',
-        %'<#{element_for(method)} #{size(method, 100)}class="form-control" #{type_for(method, type)}name="person[name]" id="person_name" />',
-        '</div>'
-      ]
+
+      expect(output).to match_form_group(default_builder_options.merge(field: :name, input_type: method, size: 100))
     end
 
     context 'when hint text provided' do
       it 'outputs hint text in span inside label' do
         output = builder.send method, :ni_number
-        expect_equal output, [
-          '<div class="form-group">',
-          '<label class="form-label" for="person_ni_number">',
-          'National Insurance number',
-          '<span class="form-hint">',
-          'It’ll be on your last payslip. For example, JH 21 90 0A.',
-          '</span>',
-          '</label>',
-          %'<#{element_for(method)} class="form-control" #{type_for(method, type)}name="person[ni_number]" id="person_ni_number" />',
-          '</div>'
-        ]
+        expect(output).to match_form_group(default_builder_options.merge(field: :ni_number, input_type: method))
       end
     end
 
@@ -121,14 +74,7 @@ def size(method, size)
         output = builder.fields_for(:address, Address.new) do |f|
           f.send method, :postcode
         end
-        expect_equal output, [
-          '<div class="form-group">',
-          '<label class="form-label" for="person_address_attributes_postcode">',
-          'Postcode',
-          '</label>',
-          %'<#{element_for(method)} class="form-control" #{type_for(method, type)}name="person[address_attributes][postcode]" id="person_address_attributes_postcode" />',
-          '</div>'
-        ]
+        expect(output).to match_form_group(default_builder_options.merge(field: :postcode, input_type: method, fields_for: :address))
       end
     end
 

spec/rails_helper.rb

@@ -21,6 +21,7 @@
 #
 # Dir[Rails.root.join('spec/support/**/*.rb')].each { |f| require f }
 require_relative 'support/translation_helper.rb'
+require_relative 'support/matcher_helpers.rb'
 
 # Checks for pending migrations before tests are run.
 # If you are not using ActiveRecord, you can remove this line.
@@ -49,4 +50,5 @@
   # The different available types are documented in the features, such as in
   # https://relishapp.com/rspec/rspec-rails/docs
   config.infer_spec_type_from_file_location!
+  config.include MatcherHelpers
 end

spec/support/matcher_helpers.rb

@@ -0,0 +1,7 @@
+require_relative 'matchers/form_group_matcher_helpers'
+
+module MatcherHelpers
+  def self.included(base)
+    base.send(:include, FormGroupMatcherHelpers)
+  end
+end

spec/support/matchers/form_group_matcher_helpers.rb

@@ -0,0 +1,115 @@
+require 'rspec/expectations'
+
+module FormGroupMatcherHelpers
+  extend RSpec::Matchers::DSL
+
+  class FormGroupObject
+    attr_reader :options, :resource, :field,
+      :label, :input_type, :input_class, :input_size,
+      :fields_for
+
+    def initialize(options)
+      @options = options
+      @resource = options[:resource]
+      @field = options.fetch(:field)
+      @label = options.fetch(:label) { @field.to_s.humanize }
+      @input_type = options.fetch(:input_type)
+      @input_class = options[:class]
+      @input_size = options[:size]
+      @fields_for = options[:fields_for]
+    end
+
+    def field_id
+      [resource, fields_for_attributes, field].compact.join('_')
+    end
+
+    def field_name
+      return "#{resource}[#{fields_for_attributes}][#{field}]" if resource && fields_for_attributes
+      return "#{resource}[#{field}]" if resource
+      field
+    end
+
+    def to_s
+      [ '<div class="form-group">', label_tag, field_tag, '</div>' ].join("\n")
+    end
+
+    private
+
+    def fields_for_attributes
+      return unless fields_for
+      "#{fields_for}_attributes"
+    end
+
+    def text_area_input?
+      input_type.to_s == 'text_area'
+    end
+
+    def input_tag
+      return '<textarea' if text_area_input?
+      '<input'
+    end
+
+    def input_tag_type
+      return if text_area_input?
+      type = {
+        text_field: 'text',
+        email_field: 'email',
+        number_field: 'number',
+        password_field: 'password',
+        phone_field: 'tel',
+        range_field: 'range',
+        search_field: 'search',
+        telephone_field: 'tel',
+        url_field: 'url'
+      }[input_type.to_sym]
+      %[type="#{type}"]
+    end
+
+    def input_tag_class
+      classes = 'form-control'
+      classes << ' ' << input_class if input_class
+      %[class="#{classes}"]
+    end
+
+    def input_tag_size
+      return if text_area_input?
+      return unless input_size
+      %[size="#{input_size}"]
+    end
+
+    def hint_tag
+      localized_path = ['helpers', 'hint', resource, field].compact.join('.')
+      localized_hint = I18n.t(localized_path, default: '')
+      return unless localized_hint.present?
+      ['<span class="form-hint">', localized_hint, '</span>'].join("\n")
+    end
+
+    def label_tag
+      localized_path = ['helpers', 'label', resource, field].compact.join('.')
+      localized_label = I18n.t(localized_path, default: field.to_s.humanize)
+      [ %[<label class="form-label" for="#{field_id}">], localized_label, hint_tag, '</label>' ].compact.join("\n")
+    end
+
+    def field_tag
+      [ input_tag, input_tag_size, input_tag_class, input_tag_type, %[name="#{field_name}"], %[id="#{field_id}"], '/>'].compact.join(' ')
+    end
+  end
+
+  matcher :match_form_group do |expected|
+    define_method :formatted_expected do
+      FormGroupObject.new(expected).to_s
+    end
+
+    define_method :formatted_actual do |actual|
+      actual.gsub(">\n</textarea>", ' />').split("<").join("\n<").split(">").join(">\n").squeeze("\n").strip + '>'
+    end
+
+    match do |actual|
+      formatted_actual(actual) == formatted_expected
+		end
+
+    failure_message do |actual|
+      "expected\n#{formatted_actual(actual)}\nto match\n#{formatted_expected}"
+    end
+  end
+end