Add NumbersHelper tests

spec/helpers/numbers_helper_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe NumbersHelper do
+  describe '#limited_counter_with_delimiter' do
+    using RSpec::Parameterized::TableSyntax
+
+    subject { limited_counter_with_delimiter(resource, **options) }
+
+    where(:count, :options, :expected_result) do
+      # Using explicit limit
+      9    | { limit: 10 } | '9'
+      10   | { limit: 10 } | '10'
+      11   | { limit: 10 } | '10+'
+      12   | { limit: 10 } | '10+'
+      # Using default limit
+      999  | {}            | '999'
+      1000 | {}            | '1,000'
+      1001 | {}            | '1,000+'
+      1002 | {}            | '1,000+'
+    end
+
+    with_them do
+      let(:page) { double('page', total_count_with_limit: [count, options.fetch(:limit, 1000) + 1].min) }
+      let(:resource) { class_double(Ci::Runner, page: page) }
+
+      it { is_expected.to eq(expected_result) }
+    end
+  end
+end