diff --git a/spec/controllers/projects/environments_controller_spec.rb b/spec/controllers/projects/environments_controller_spec.rb
index 20f99b209eb..12efdc700c5 100644
--- a/spec/controllers/projects/environments_controller_spec.rb
+++ b/spec/controllers/projects/environments_controller_spec.rb
@@ -311,6 +311,46 @@ describe Projects::EnvironmentsController do
     end
   end
 
+  describe 'GET #additional_metrics' do
+    before do
+      allow(controller).to receive(:environment).and_return(environment)
+    end
+
+    context 'when environment has no metrics' do
+      before do
+        expect(environment).to receive(:additional_metrics).and_return(nil)
+      end
+
+      context 'when requesting metrics as JSON' do
+        it 'returns a metrics JSON document' do
+          get :additional_metrics, environment_params(format: :json)
+
+          expect(response).to have_http_status(204)
+          expect(json_response).to eq({})
+        end
+      end
+    end
+
+    context 'when environment has some metrics' do
+      before do
+        expect(environment).to receive(:additional_metrics).and_return({
+                                                              success: true,
+                                                              data: {},
+                                                              last_update: 42
+                                                            })
+      end
+
+      it 'returns a metrics JSON document' do
+        get :additional_metrics, environment_params(format: :json)
+
+        expect(response).to be_ok
+        expect(json_response['success']).to be(true)
+        expect(json_response['data']).to eq({})
+        expect(json_response['last_update']).to eq(42)
+      end
+    end
+  end
+
   def environment_params(opts = {})
     opts.reverse_merge(namespace_id: project.namespace,
                        project_id: project,
diff --git a/spec/models/environment_spec.rb b/spec/models/environment_spec.rb
index 12519de8636..12de9c9111b 100644
--- a/spec/models/environment_spec.rb
+++ b/spec/models/environment_spec.rb
@@ -409,6 +409,99 @@ describe Environment, models: true do
     end
   end
 
+  describe '#has_metrics?' do
+    subject { environment.has_metrics? }
+
+    context 'when the enviroment is available' do
+      context 'with a deployment service' do
+        let(:project) { create(:prometheus_project) }
+
+        context 'and a deployment' do
+          let!(:deployment) { create(:deployment, environment: environment) }
+          it { is_expected.to be_truthy }
+        end
+
+        context 'but no deployments' do
+          it { is_expected.to be_falsy }
+        end
+      end
+
+      context 'without a monitoring service' do
+        it { is_expected.to be_falsy }
+      end
+    end
+
+    context 'when the environment is unavailable' do
+      let(:project) { create(:prometheus_project) }
+
+      before do
+        environment.stop
+      end
+
+      it { is_expected.to be_falsy }
+    end
+  end
+
+  describe '#additional_metrics' do
+    let(:project) { create(:prometheus_project) }
+    subject { environment.additional_metrics }
+
+    context 'when the environment has additional metrics' do
+      before do
+        allow(environment).to receive(:has_additional_metrics?).and_return(true)
+      end
+
+      it 'returns the additional metrics from the deployment service' do
+        expect(project.monitoring_service).to receive(:reactive_query)
+                                                .with(Gitlab::Prometheus::Queries::AdditionalMetricsQuery.name, environment.id)
+                                                .and_return(:fake_metrics)
+
+        is_expected.to eq(:fake_metrics)
+      end
+    end
+
+    context 'when the environment does not have metrics' do
+      before do
+        allow(environment).to receive(:has_additional_metrics?).and_return(false)
+      end
+
+      it { is_expected.to be_nil }
+    end
+  end
+
+  describe '#has_additional_metrics??' do
+    subject { environment.has_metrics? }
+
+    context 'when the enviroment is available' do
+      context 'with a deployment service' do
+        let(:project) { create(:prometheus_project) }
+
+        context 'and a deployment' do
+          let!(:deployment) { create(:deployment, environment: environment) }
+          it { is_expected.to be_truthy }
+        end
+
+        context 'but no deployments' do
+          it { is_expected.to be_falsy }
+        end
+      end
+
+      context 'without a monitoring service' do
+        it { is_expected.to be_falsy }
+      end
+    end
+
+    context 'when the environment is unavailable' do
+      let(:project) { create(:prometheus_project) }
+
+      before do
+        environment.stop
+      end
+
+      it { is_expected.to be_falsy }
+    end
+  end
+
   describe '#slug' do
     it "is automatically generated" do
       expect(environment.slug).not_to be_nil