Improve labels methods

Add option to send array to mr_has_label? and add tests
Refactor tests to use context

danger/telemetry/Dangerfile

@@ -11,22 +11,13 @@ MSG
 
 usage_data_changed_files = git.modified_files.grep(%r{usage_data})
 
-def has_label?(label)
-  gitlab.mr_labels.include?(label)
-end
-
-def labels_for_merge_request(labels)
-  labels_list = labels.map { |label| %Q{~"#{label}"} }.join(' ')
-  "/label #{labels_list}"
-end
-
 if usage_data_changed_files.any?
   warn format(TELEMETRY_CHANGED_FILES_MESSAGE)
 
   markdown(USAGE_DATA_FILES_MESSAGE + helper.markdown_list(usage_data_changed_files))
 
   telemetry_labels = ['telemetry']
-  telemetry_labels << 'telemetry::review pending' unless has_label?('telemetry::reviewed')
+  telemetry_labels << 'telemetry::review pending' unless helper.mr_has_labels?('telemetry::reviewed')
 
-  markdown(labels_for_merge_request(telemetry_labels))
+  markdown(helper.prepare_labels_for_mr(telemetry_labels))
 end

lib/gitlab/danger/helper.rb

@@ -191,6 +191,20 @@ module Gitlab
         gitlab_helper.mr_json['web_url'].include?('/gitlab-org/security/')
       end
 
+      def mr_has_labels?(*labels)
+        return false unless gitlab_helper
+
+        labels = labels.flatten.uniq
+        (labels & gitlab_helper.mr_labels) == labels
+      end
+
+      def prepare_labels_for_mr(labels)
+        return '' unless labels.any?
+
+        labels_list = labels.map { |label| %Q{~"#{label}"} }.join(' ')
+        "/label #{labels_list}"
+      end
+
       private
 
       def has_database_scoped_labels?(current_mr_labels)

spec/lib/gitlab/danger/helper_spec.rb

@@ -363,4 +363,50 @@ describe Gitlab::Danger::Helper do
       expect(helper).to be_security_mr
     end
   end
+
+  describe '#mr_has_label?' do
+    it 'returns false when `gitlab_helper` is unavailable' do
+      expect(helper).to receive(:gitlab_helper).and_return(nil)
+
+      expect(helper.mr_has_labels?('telemetry')).to be_falsey
+    end
+
+    context 'when mr has labels' do
+      before do
+        mr_labels = ['telemetry', 'telemetry::reviewed']
+        expect(fake_gitlab).to receive(:mr_labels).and_return(mr_labels)
+      end
+
+      it 'returns true with a matched label' do
+        expect(helper.mr_has_labels?('telemetry')).to be_truthy
+      end
+
+      it 'returns false with unmatched label' do
+        expect(helper.mr_has_labels?('database')).to be_falsey
+      end
+
+      it 'returns true with an array of labels' do
+        expect(helper.mr_has_labels?(['telemetry', 'telemetry::reviewed'])).to be_truthy
+      end
+
+      it 'returns true with multi arguments with matched labels' do
+        expect(helper.mr_has_labels?('telemetry', 'telemetry::reviewed')).to be_truthy
+      end
+
+      it 'returns false with multi arguments with unmatched labels' do
+        expect(helper.mr_has_labels?('telemetry', 'telemetry::non existing')).to be_falsey
+      end
+    end
+  end
+
+  describe '#prepare_labels_for_mr' do
+    it 'composes the labels string' do
+      mr_labels = ['telemetry', 'telemetry::reviewed']
+      expect(helper.prepare_labels_for_mr(mr_labels)).to eq('/label ~"telemetry" ~"telemetry::reviewed"')
+    end
+
+    it 'returns empty string for empty array' do
+      expect(helper.prepare_labels_for_mr([])).to eq('')
+    end
+  end
 end