Add cop for duplicate testcase links

rubocop/cop/qa/duplicate_testcase_link.rb

+# frozen_string_literal: true
+
+require_relative '../../qa_helpers'
+
+module RuboCop
+  module Cop
+    module QA
+      # This cop checks for duplicate testcase links across e2e specs
+      #
+      # @example
+      #
+      #   # bad
+      #   it 'some test', testcase: '(...)/quality/test_cases/1892'
+      #   it 'another test, testcase: '(...)/quality/test_cases/1892'
+      #
+      #   # good
+      #   it 'some test', testcase: '(...)/quality/test_cases/1892'
+      #   it 'another test, testcase: '(...)/quality/test_cases/1894'
+      class DuplicateTestcaseLink < RuboCop::Cop::Cop
+        include QAHelpers
+
+        MESSAGE = "Don't reuse the same testcase link in different tests. Replace one of `%s`."
+
+        @testcase_set = Set.new
+
+        def_node_matcher :duplicate_testcase_link, <<~PATTERN
+          (block
+            (send nil? ...
+              ...
+              (hash
+                (pair
+                  (sym :testcase)
+                  (str $_))...)...)...)
+        PATTERN
+
+        def on_block(node)
+          return unless in_qa_file?(node)
+
+          duplicate_testcase_link(node) do |link|
+            break unless self.class.duplicate?(link)
+
+            add_offense(node, message: MESSAGE % link)
+          end
+        end
+
+        def self.duplicate?(link)
+          !@testcase_set.add?(link)
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/qa/duplicate_testcase_link_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+require_relative '../../../../rubocop/cop/qa/duplicate_testcase_link'
+
+RSpec.describe RuboCop::Cop::QA::DuplicateTestcaseLink do
+  let(:source_file) { 'qa/page.rb' }
+
+  subject(:cop) { described_class.new }
+
+  context 'in a QA file' do
+    before do
+      allow(cop).to receive(:in_qa_file?).and_return(true)
+    end
+
+    it "registers an offense for a duplicate testcase link" do
+      expect_offense(<<-RUBY)
+        it 'some test', testcase: '/quality/test_cases/1892' do
+        end
+        it 'another test', testcase: '/quality/test_cases/1892' do
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't reuse the same testcase link in different tests. Replace one of `/quality/test_cases/1892`.
+        end
+      RUBY
+    end
+
+    it "doesnt offend if testcase link is unique" do
+      expect_no_offenses(<<-RUBY)
+        it 'some test', testcase: '/quality/test_cases/1893' do
+        end
+        it 'another test', testcase: '/quality/test_cases/1894' do
+        end
+      RUBY
+    end
+  end
+end