Add small option to radio component

app/views/govuk_publishing_components/components/_radio.html.erb

@@ -4,6 +4,7 @@
 
   label ||= nil
   heading ||= nil
+  small ||= false
   is_page_heading ||= false
   hint ||= nil
   error_message ||= nil
@@ -16,6 +17,9 @@
   form_group_css_classes = %w(govuk-form-group)
   form_group_css_classes << "govuk-form-group--error" if has_error
 
+  radio_classes = %w(govuk-radios)
+  radio_classes << "govuk-radios--small" if small
+
   aria = "#{hint_id} #{"#{error_id}" if has_error}".strip if hint or has_error
 
   # check if any item is set as being conditional
@@ -53,7 +57,7 @@
       } %>
     <% end %>
 
-    <%= content_tag :div, class: "govuk-radios",
+    <%= content_tag :div, class: radio_classes,
       data: {
         module: ('radios' if has_conditional)
       } do %>

app/views/govuk_publishing_components/components/docs/radio.yml

@@ -44,6 +44,15 @@ examples:
         text: "Use Government Gateway"
       - value: "govuk-verify"
         text: "Use GOV.UK Verify"
+  with_small_radios:
+    data:
+      name: "radio-group"
+      small: true
+      items:
+      - value: "government-gateway"
+        text: "Use Government Gateway"
+      - value: "govuk-verify"
+        text: "Use GOV.UK Verify"
   with_bold:
     description: 'Used to provide better contrast between long labels and hint text, Note that the `:or` option [is documented as a string due to a bug](https://github.com/alphagov/govuk_publishing_components/issues/102)'
     data:

spec/components/radio_spec.rb

@@ -53,6 +53,25 @@ def component_name
     assert_select ".govuk-radios__item:last-child .govuk-radios__label", text: "Use GOV.UK Verify"
   end
 
+  it "renders small radios" do
+    render_component(
+      name: "radio-group-multiple-items",
+      small: true,
+      items: [
+        {
+          value: "government-gateway",
+          text: "Use Government Gateway"
+        },
+        {
+          value: "govuk-verify",
+          text: "Use GOV.UK Verify"
+        }
+      ]
+    )
+
+    assert_select ".govuk-radios.govuk-radios--small"
+  end
+
   it "renders radio-group with a legend" do
     render_component(
       name: "favourite-smartie",