1 files changed, 51 insertions, 0 deletions
diff --git a/spec/controllers/concerns/preferred_language_switcher_spec.rb b/spec/controllers/concerns/preferred_language_switcher_spec.rb
new file mode 100644
index 00000000000..40d6ac10c37
--- /dev/null
+++ b/spec/controllers/concerns/preferred_language_switcher_spec.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe PreferredLanguageSwitcher, type: :controller do
+  controller(ActionController::Base) do
+    include PreferredLanguageSwitcher # rubocop:disable RSpec/DescribedClass
+
+    before_action :init_preferred_language, only: :new
+
+    def new
+      render html: 'new page'
+    end
+  end
+
+  context 'when first visit' do
+    before do
+      get :new
+    end
+
+    it 'sets preferred_language to default' do
+      expect(cookies[:preferred_language]).to eq Gitlab::CurrentSettings.default_preferred_language
+    end
+  end
+
+  context 'when preferred language in cookies has been modified' do
+    let(:user_preferred_language) { nil }
+
+    before do
+      cookies[:preferred_language] = user_preferred_language
+
+      get :new
+    end
+
+    context 'with a valid value' do
+      let(:user_preferred_language) { 'zh_CN' }
+
+      it 'keeps preferred language unchanged' do
+        expect(cookies[:preferred_language]).to eq user_preferred_language
+      end
+    end
+
+    context 'with an invalid value' do
+      let(:user_preferred_language) { 'xxx' }
+
+      it 'sets preferred_language to default' do
+        expect(cookies[:preferred_language]).to eq Gitlab::CurrentSettings.default_preferred_language
+      end
+    end
+  end
+end