Extract GET #metrics_dashboard to shared examples

In order to reuse common behaviour test, we need to extract it to
shaerd examples.

spec/controllers/projects/environments_controller_spec.rb

@@ -546,28 +546,20 @@ RSpec.describe Projects::EnvironmentsController do
   end
 
   describe 'GET #metrics_dashboard' do
-    shared_examples_for 'correctly formatted response' do |status_code|
-      it 'returns a json object with the correct keys' do
-        get :metrics_dashboard, params: environment_params(dashboard_params)
-
-        # Exlcude `all_dashboards` to handle separately.
-        found_keys = json_response.keys - ['all_dashboards']
-
-        expect(response).to have_gitlab_http_status(status_code)
-        expect(found_keys).to contain_exactly(*expected_keys)
-      end
-    end
+    let(:metrics_dashboard_req_params) { environment_params(dashboard_params) }
 
     shared_examples_for '200 response' do
-      let(:expected_keys) { %w(dashboard status metrics_data) }
-
-      it_behaves_like 'correctly formatted response', :ok
+      it_behaves_like 'GET #metrics_dashboard correctly formatted response' do
+        let(:expected_keys) { %w(dashboard status metrics_data) }
+        let(:status_code) { :ok }
+      end
     end
 
     shared_examples_for 'error response' do |status_code|
-      let(:expected_keys) { %w(message status) }
-
-      it_behaves_like 'correctly formatted response', status_code
+      it_behaves_like 'GET #metrics_dashboard correctly formatted response' do
+        let(:expected_keys) { %w(message status) }
+        let(:status_code) { status_code }
+      end
     end
 
     shared_examples_for 'includes all dashboards' do
@@ -581,29 +573,14 @@ RSpec.describe Projects::EnvironmentsController do
     end
 
     shared_examples_for 'the default dashboard' do
-      it_behaves_like '200 response'
       it_behaves_like 'includes all dashboards'
-
-      it 'is the default dashboard' do
-        get :metrics_dashboard, params: environment_params(dashboard_params)
-
-        expect(json_response['dashboard']['dashboard']).to eq('Environment metrics')
-      end
+      it_behaves_like 'GET #metrics_dashboard for dashboard', 'Environment metrics'
     end
 
     shared_examples_for 'the specified dashboard' do |expected_dashboard|
-      it_behaves_like '200 response'
       it_behaves_like 'includes all dashboards'
 
-      it 'has the correct name' do
-        get :metrics_dashboard, params: environment_params(dashboard_params)
-
-        dashboard_name = json_response['dashboard']['dashboard']
-
-        # 'Environment metrics' is the default dashboard.
-        expect(dashboard_name).not_to eq('Environment metrics')
-        expect(dashboard_name).to eq(expected_dashboard)
-      end
+      it_behaves_like 'GET #metrics_dashboard for dashboard', expected_dashboard
 
       context 'when the dashboard cannot not be processed' do
         before do

spec/support/shared_examples/controllers/metrics_dashboard_shared_examples.rb

+# frozen_string_literal: true
+
+RSpec.shared_examples_for 'GET #metrics_dashboard correctly formatted response' do
+  it 'returns a json object with the correct keys' do
+    get :metrics_dashboard, params: metrics_dashboard_req_params, format: :json
+
+    # Exlcude `all_dashboards` to handle separately.
+    found_keys = json_response.keys - ['all_dashboards']
+
+    expect(response).to have_gitlab_http_status(status_code)
+    expect(found_keys).to contain_exactly(*expected_keys)
+  end
+end
+
+RSpec.shared_examples_for 'GET #metrics_dashboard for dashboard' do |dashboard_name|
+  let(:expected_keys) { %w(dashboard status metrics_data) }
+  let(:status_code) { :ok }
+
+  it_behaves_like 'GET #metrics_dashboard correctly formatted response'
+
+  it 'returns correct dashboard' do
+    get :metrics_dashboard, params: metrics_dashboard_req_params, format: :json
+
+    expect(json_response['dashboard']['dashboard']).to eq(dashboard_name)
+  end
+end