Add coverage for api/v1 controllers (#3155)

spec/controllers/api/v1/instances_controller_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Api::V1::InstancesController, type: :controller do
+  render_views
+
+  let(:user)  { Fabricate(:user, account: Fabricate(:account, username: 'alice')) }
+  let(:token) { double acceptable?: true, resource_owner_id: user.id }
+
+  before do
+    allow(controller).to receive(:doorkeeper_token) { token }
+  end
+
+  describe 'GET #show' do
+    it 'returns http success' do
+      get :show
+
+      expect(response).to have_http_status(:success)
+    end
+  end
+end