Add specs for Gitlab::SidekiqConfig::CliMethods

By using `fast_spec_helper`, we also do a better job of testing that
these methods don't expect un-required files to be
available. `.worker_queues` is tested here and in the specs for
Gitlab::SidekiqConfig, as in the latter it's using the actual YAML
files, rather than stubbed ones as added here.

lib/gitlab/sidekiq_config/cli_methods.rb

@@ -37,6 +37,12 @@ module Gitlab
           [queue, *queues_set.grep(/\A#{queue}:/)]
         end
       end
+
+      def clear_memoization!
+        if instance_variable_defined?('@worker_queues')
+          remove_instance_variable('@worker_queues')
+        end
+      end
       # rubocop:enable Gitlab/ModuleWithInstanceVariables
     end
   end

spec/lib/gitlab/sidekiq_config/cli_methods_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+describe Gitlab::SidekiqConfig::CliMethods do
+  let(:dummy_root) { '/tmp/' }
+
+  describe '.worker_queues' do
+    def expand_path(path)
+      File.join(dummy_root, path)
+    end
+
+    def stub_exists(exists: true)
+      ['app/workers/all_queues.yml', 'ee/app/workers/all_queues.yml'].each do |path|
+        allow(File).to receive(:exist?).with(expand_path(path)).and_return(exists)
+      end
+    end
+
+    def stub_contents(foss_queues, ee_queues)
+      allow(YAML).to receive(:load_file)
+                       .with(expand_path('app/workers/all_queues.yml'))
+                       .and_return(foss_queues)
+
+      allow(YAML).to receive(:load_file)
+                       .with(expand_path('ee/app/workers/all_queues.yml'))
+                       .and_return(ee_queues)
+    end
+
+    before do
+      described_class.clear_memoization!
+    end
+
+    context 'when the file exists' do
+      before do
+        stub_exists(exists: true)
+        stub_contents(['queue_a'], ['queue_b'])
+      end
+
+      it 'memoizes the result' do
+        result = described_class.worker_queues(dummy_root)
+
+        stub_exists(exists: false)
+
+        expect(described_class.worker_queues(dummy_root)).to eq(result)
+      end
+
+      it 'flattens and joins the contents' do
+        expect(described_class.worker_queues(dummy_root))
+          .to contain_exactly('queue_a', 'queue_b')
+      end
+    end
+
+    context 'when the file does not exist' do
+      before do
+        stub_exists(exists: false)
+      end
+
+      it 'returns an empty array' do
+        expect(described_class.worker_queues(dummy_root)).to be_empty
+      end
+    end
+  end
+
+  describe '.expand_queues' do
+    let(:all_queues) do
+      ['cronjob:stuck_import_jobs', 'cronjob:stuck_merge_jobs', 'post_receive']
+    end
+
+    it 'defaults the value of the second argument to .worker_queues' do
+      allow(described_class).to receive(:worker_queues).and_return([])
+
+      expect(described_class.expand_queues(['cronjob']))
+        .to contain_exactly('cronjob')
+
+      allow(described_class).to receive(:worker_queues).and_return(all_queues)
+
+      expect(described_class.expand_queues(['cronjob']))
+        .to contain_exactly('cronjob', 'cronjob:stuck_import_jobs', 'cronjob:stuck_merge_jobs')
+    end
+
+    it 'expands queue namespaces to concrete queue names' do
+      expect(described_class.expand_queues(['cronjob'], all_queues))
+        .to contain_exactly('cronjob', 'cronjob:stuck_import_jobs', 'cronjob:stuck_merge_jobs')
+    end
+
+    it 'lets concrete queue names pass through' do
+      expect(described_class.expand_queues(['post_receive'], all_queues))
+        .to contain_exactly('post_receive')
+    end
+
+    it 'lets unknown queues pass through' do
+      expect(described_class.expand_queues(['unknown'], all_queues))
+        .to contain_exactly('unknown')
+    end
+  end
+end

spec/lib/gitlab/sidekiq_config_spec.rb

@@ -24,27 +24,6 @@ describe Gitlab::SidekiqConfig do
     end
   end
 
-  describe '.expand_queues' do
-    it 'expands queue namespaces to concrete queue names' do
-      queues = described_class.expand_queues(%w[cronjob])
-
-      expect(queues).to include('cronjob:stuck_import_jobs')
-      expect(queues).to include('cronjob:stuck_merge_jobs')
-    end
-
-    it 'lets concrete queue names pass through' do
-      queues = described_class.expand_queues(%w[post_receive])
-
-      expect(queues).to include('post_receive')
-    end
-
-    it 'lets unknown queues pass through' do
-      queues = described_class.expand_queues(%w[unknown])
-
-      expect(queues).to include('unknown')
-    end
-  end
-
   describe '.workers_for_all_queues_yml' do
     it 'returns a tuple with FOSS workers first' do
       expect(described_class.workers_for_all_queues_yml.first)