Allow the back link component to take blocks

app/components/govuk_component/back_link_component.rb

@@ -1,19 +1,23 @@
 class GovukComponent::BackLinkComponent < GovukComponent::Base
   attr_reader :text, :href
 
-  def initialize(text:, href:, classes: nil, html_attributes: {})
+  def initialize(href:, text: nil, classes: nil, html_attributes: {})
     super(classes: classes, html_attributes: html_attributes)
 
     @text = text
     @href = href
   end
 
   def call
-    link_to(text, href, class: classes, **html_attributes)
+    link_to(link_content, href, class: classes, **html_attributes)
   end
 
 private
 
+  def link_content
+    text || content || fail(ArgumentError, "no text or content")
+  end
+
   def default_classes
     %w(govuk-back-link)
   end

spec/components/govuk_component/back_link_component_spec.rb

@@ -1,6 +1,7 @@
 require 'spec_helper'
 
 RSpec.describe(GovukComponent::BackLinkComponent, type: :component) do
+  include_context 'helpers'
   include_context 'setup'
 
   let(:text) { 'Department for Education' }
@@ -14,6 +15,30 @@
     expect(rendered_component).to have_tag('a', text: text, with: { href: href, class: component_css_class })
   end
 
+  context 'when link text is provided via a block' do
+    let(:custom_text) { "Some text" }
+    let(:custom_tag) { :code }
+    subject! do
+      render_inline(GovukComponent::BackLinkComponent.new(href: href)) do
+        helper.content_tag(custom_tag, custom_text)
+      end
+    end
+
+    specify 'renders the component with custom tag and text' do
+      expect(rendered_component).to have_tag('a', with: { href: href, class: component_css_class }) do
+        with_tag(custom_tag, text: custom_text)
+      end
+    end
+  end
+
+  context "when neither text or a block is supplied" do
+    specify "raises an appropriate error" do
+      expect {
+        render_inline(GovukComponent::BackLinkComponent.new(href: href))
+      }.to raise_error(ArgumentError, "no text or content")
+    end
+  end
+
   it_behaves_like 'a component that accepts custom classes'
   it_behaves_like 'a component that accepts custom HTML attributes'
 end