Stop UniqueIdentifierGenerator from being a Singleton

It no longer needs to be as its lifecycle is now fully tied to the Redcarpet renderer

Author: romaricpascal

lib/govuk_tech_docs/tech_docs_html_renderer.rb

@@ -12,7 +12,7 @@ def initialize(options = {})
     end
 
     def preprocess(document)
-      UniqueIdentifierGenerator.instance.reset
+      @unique_identifier_generator = UniqueIdentifierGenerator.new
 
       document
     end
@@ -22,7 +22,7 @@ def paragraph(text)
     end
 
     def header(text, level)
-      anchor = UniqueIdentifierGenerator.instance.create(text, level)
+      anchor = @unique_identifier_generator.create(text, level)
       %(<h#{level} id="#{anchor}">#{text}</h#{level}>\n)
     end
 

lib/govuk_tech_docs/unique_identifier_generator.rb

@@ -1,15 +1,11 @@
-require "singleton"
-
 module GovukTechDocs
   class UniqueIdentifierGenerator
-    include Singleton
-
     Anchor = Struct.new(:id, :level)
 
     attr_reader :anchors
 
     def initialize
-      reset
+      @anchors = []
     end
 
     def create(id, level)
@@ -28,10 +24,6 @@ def create(id, level)
       anchor
     end
 
-    def reset
-      @anchors = []
-    end
-
   private
 
     def prefixed_by_parent(anchor, level)

spec/govuk_tech_docs/tech_docs_html_renderer_spec.rb

@@ -97,9 +97,6 @@ def hello_world
   end
 
   describe "#render unique heading IDs" do
-    # Reset the UniqueIdentifierGenerator between each tests to ensure independence
-    before(:each) { GovukTechDocs::UniqueIdentifierGenerator.instance.reset }
-
     it "Automatically assigns an ID to the heading" do
       output = processor.render <<~MARKDOWN
         # A heading

spec/govuk_tech_docs/unique_identifier_generator_spec.rb

@@ -1,6 +1,5 @@
 RSpec.describe GovukTechDocs::UniqueIdentifierGenerator do
-  subject { described_class.instance }
-  before { subject.reset }
+  subject { described_class.new }
 
   describe "#create" do
     it "lower-cases the text" do
@@ -66,13 +65,4 @@
       end
     end
   end
-
-  describe "#reset" do
-    it "clears the list of existing anchors" do
-      subject.create("An Anchor", 1)
-      expect(subject.anchors).to_not be_empty
-      subject.reset
-      expect(subject.anchors).to be_empty
-    end
-  end
 end