Refactor resolver and spec

Refactor the resolver to be more clear about
what each code section is doing.

Include authorization for reading builds in resolver.

Refactor a few areas in the spec file to make
things a little more simple.

app/graphql/resolvers/ci/test_suite_resolver.rb

@@ -3,6 +3,9 @@
 module Resolvers
   module Ci
     class TestSuiteResolver < BaseResolver
+      include Gitlab::Graphql::Authorize::AuthorizeResource
+
+      authorize :read_build
       type ::Types::Ci::TestSuiteType, null: true
 
       alias_method :pipeline, :object
@@ -13,17 +16,23 @@ module Resolvers
 
       def resolve(build_ids:)
         builds = pipeline.latest_builds.id_in(build_ids).presence
-        return if builds.nil? || builds.empty?
+        return unless builds
+
+        TestSuiteSerializer
+          .new(project: pipeline.project, current_user: @current_user)
+          .represent(load_test_suite_data(builds), details: true)
+      end
+
+      private
 
+      def load_test_suite_data(builds)
         suite = builds.sum do |build|
           build.collect_test_reports!(Gitlab::Ci::Reports::TestReports.new)
         end
 
         Gitlab::Ci::Reports::TestFailureHistory.new(suite.failed.values, pipeline.project).load!
 
-        TestSuiteSerializer
-          .new(project: pipeline.project, current_user: @current_user)
-          .represent(suite, details: true)
+        suite
       end
     end
   end

spec/graphql/resolvers/ci/test_suite_resolver_spec.rb

@@ -9,6 +9,8 @@ RSpec.describe Resolvers::Ci::TestSuiteResolver do
   let(:project) { create(:project, :public, :repository) }
 
   describe '#resolve' do
+    subject(:test_suite) { resolve(described_class, obj: pipeline, args: { build_ids: build_ids }) }
+
     context 'when pipeline has builds with test reports' do
       let(:main_pipeline) { create(:ci_pipeline, :with_test_reports_with_three_failures, project: project) }
       let(:pipeline) { create(:ci_pipeline, :with_test_reports_with_three_failures, project: project, ref: 'new-feature') }
@@ -25,8 +27,6 @@ RSpec.describe Resolvers::Ci::TestSuiteResolver do
       end
 
       it 'renders test suite data' do
-        test_suite = resolve(described_class, obj: pipeline, args: { build_ids: build_ids })
-
         expect(test_suite[:name]).to eq('test')
 
         # Each test failure in this pipeline has a matching failure in the default branch
@@ -42,11 +42,10 @@ RSpec.describe Resolvers::Ci::TestSuiteResolver do
     context 'when pipeline has no builds that matches the given build_ids' do
       let(:pipeline) { create(:ci_empty_pipeline) }
       let(:suite_name) { 'test' }
+      let(:build_ids) { [non_existing_record_id] }
 
       it 'returns nil' do
-        test_suite = resolve(described_class, obj: pipeline, args: { build_ids: ['1'] })
-
-        expect(test_suite).to eq(nil)
+        expect(test_suite).to be_nil
       end
     end
   end