Improve MetricGroup test

spec/lib/gitlab/prometheus/metric_group_spec.rb

@@ -4,10 +4,10 @@
 
 describe Gitlab::Prometheus::MetricGroup do
   describe '.common_metrics' do
-    set(:project_metric) { create(:prometheus_metric) }
-    set(:common_metric_group_a) { create(:prometheus_metric, :common, group: :aws_elb) }
-    set(:common_metric_group_b_q1) { create(:prometheus_metric, :common, group: :kubernetes) }
-    set(:common_metric_group_b_q2) { create(:prometheus_metric, :common, group: :kubernetes) }
+    let!(:project_metric) { create(:prometheus_metric) }
+    let!(:common_metric_group_a) { create(:prometheus_metric, :common, group: :aws_elb) }
+    let!(:common_metric_group_b_q1) { create(:prometheus_metric, :common, group: :kubernetes) }
+    let!(:common_metric_group_b_q2) { create(:prometheus_metric, :common, group: :kubernetes) }
 
     subject { described_class.common_metrics }
 
@@ -16,9 +16,21 @@
     end
 
     it 'returns exactly three metric queries' do
-      expect(subject.map(&:metrics).flatten.map(&:queries)).to contain_exactly(
-        common_metric_group_a.queries, common_metric_group_b_q1.queries,
-        common_metric_group_b_q2.queries)
+      expect(subject.map(&:metrics).flatten.map(&:id)).to contain_exactly(
+        common_metric_group_a.id, common_metric_group_b_q1.id,
+        common_metric_group_b_q2.id)
+    end
+  end
+
+  describe '.for_project' do
+    let!(:other_project) { create(:project) }
+    let!(:project_metric) { create(:prometheus_metric) }
+    let!(:common_metric) { create(:prometheus_metric, :common, group: :aws_elb) }
+
+    subject { described_class.for_project(other_project) }
+
+    it 'returns exactly one common metric' do
+      expect(subject.map(&:metrics).flatten.map(&:id)).to contain_exactly(common_metric.id)
     end
   end
 end