Improve spec for dimension/languages admin metric (#29842)

spec/lib/admin/metrics/dimension/languages_dimension_spec.rb

@@ -3,7 +3,7 @@
 require 'rails_helper'
 
 describe Admin::Metrics::Dimension::LanguagesDimension do
-  subject(:dimension) { described_class.new(start_at, end_at, limit, params) }
+  subject { described_class.new(start_at, end_at, limit, params) }
 
   let(:start_at) { 2.days.ago }
   let(:end_at) { Time.now.utc }
@@ -11,8 +11,21 @@ describe Admin::Metrics::Dimension::LanguagesDimension do
   let(:params) { ActionController::Parameters.new }
 
   describe '#data' do
-    it 'runs data query without error' do
-      expect { dimension.data }.to_not raise_error
+    let(:alice) { Fabricate(:user, locale: 'en', current_sign_in_at: 1.day.ago) }
+    let(:bob) { Fabricate(:user, locale: 'en', current_sign_in_at: 30.days.ago) }
+
+    before do
+      alice.update(current_sign_in_at: 1.day.ago)
+      bob.update(current_sign_in_at: 30.days.ago)
+    end
+
+    it 'returns locales with sign in counts' do
+      expect(subject.data.size)
+        .to eq(1)
+      expect(subject.data.map(&:symbolize_keys))
+        .to contain_exactly(
+          include(key: 'en', value: '1')
+        )
     end
   end
 end