Added BilledUsersFinder class

Added rspec accordingly.

ee/app/finders/billed_users_finder.rb

+# frozen_string_literal: true
+
+class BilledUsersFinder
+  def initialize(group, search_term: nil, order_by: 'name_asc')
+    @group = group
+    @search_term = search_term
+    @order_by = order_by
+  end
+
+  def execute
+    return [] unless group_billed_user_ids.any?
+
+    users = ::User.id_in(group_billed_user_ids)
+    users = users.search(search_term) if search_term
+
+    users.sort_by_attribute(order_by)
+  end
+
+  private
+
+  attr_reader :group, :search_term, :order_by
+
+  def group_billed_user_ids
+    @group_billed_user_ids ||= group.billed_user_ids
+  end
+end

ee/lib/ee/api/helpers/members_helpers.rb

@@ -83,13 +83,6 @@ module EE
             action: :create
           ).for_member(member).security_event
         end
-
-        def billed_users_for(group, search_term, order_by: 'name_asc')
-          users = ::User.id_in(group.billed_user_ids)
-          users = users.search(search_term) if search_term
-
-          users.sort_by_attribute(order_by)
-        end
       end
     end
   end

ee/lib/ee/api/members.rb

@@ -57,7 +57,11 @@ module EE
             bad_request!(nil) unless ::Ability.allowed?(current_user, :admin_group_member, group)
 
             sorting = params[:sort] || 'id_asc'
-            users = paginate(billed_users_for(group, params[:search], order_by: sorting))
+            users = paginate(
+              BilledUsersFinder.new(group,
+                                    search_term: params[:search],
+                                    order_by: sorting).execute
+            )
 
             present users, with: ::API::Entities::UserBasic, current_user: current_user
           end

ee/spec/finders/billed_users_finder_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe BilledUsersFinder do
+  let_it_be(:group) { create(:group) }
+  let(:search_term) { nil }
+  let(:order_by) { nil }
+
+  describe '#execute' do
+    let_it_be(:maria) { create(:group_member, group: group, user: create(:user, name: 'Maria Gomez')) }
+    let_it_be(:john_smith) { create(:group_member, group: group, user: create(:user, name: 'John Smith')) }
+    let_it_be(:john_doe) { create(:group_member, group: group, user: create(:user, name: 'John Doe')) }
+    let_it_be(:sophie) { create(:group_member, group: group, user: create(:user, name: 'Sophie Dupont')) }
+
+    subject { described_class.new(group, search_term: search_term, order_by: order_by) }
+
+    context 'when a group does not have any billed users' do
+      it 'returns an empty array' do
+        allow(group).to receive(:billed_user_ids).and_return([])
+
+        expect(subject.execute).to be_empty
+      end
+    end
+
+    context 'when a search parameter is provided' do
+      let(:search_term) { 'John' }
+
+      context 'when a sorting parameter is provided (eg name descending)' do
+        let(:order_by) { 'name_desc' }
+
+        it 'sorts results accordingly' do
+          expect(subject.execute).to eq([john_smith, john_doe].map(&:user))
+        end
+      end
+    end
+
+    context 'when a search parameter is not present' do
+      subject { described_class.new(group) }
+
+      it 'returns expected users in name asc order when a sorting is not provided either' do
+        allow(group).to receive(:billed_user_members).and_return([john_doe, john_smith, sophie, maria])
+
+        expect(subject.execute).to eq([john_doe, john_smith, maria, sophie].map(&:user))
+      end
+
+      context 'and when a sorting parameter is provided (eg name descending)' do
+        let(:order_by) { 'name_desc' }
+
+        subject { described_class.new(group, search_term: search_term, order_by: order_by) }
+
+        it 'sorts results accordingly' do
+          expect(subject.execute).to eq([sophie, maria, john_smith, john_doe].map(&:user))
+        end
+      end
+    end
+  end
+end

ee/spec/lib/ee/api/helpers/members_helpers_spec.rb

@@ -33,56 +33,4 @@ RSpec.describe EE::API::Helpers::MembersHelpers do
       let(:member) { create(:project_member, project: source, user: create(:user)) }
     end
   end
-
-  describe '#billed_users_for' do
-    let_it_be(:group) { create(:group) }
-    let_it_be(:maria) { create(:group_member, group: group, user: create(:user, name: 'Maria Gomez')) }
-    let_it_be(:john_smith) { create(:group_member, group: group, user: create(:user, name: 'John Smith')) }
-    let_it_be(:john_doe) { create(:group_member, group: group, user: create(:user, name: 'John Doe')) }
-    let_it_be(:sophie) { create(:group_member, group: group, user: create(:user, name: 'Sophie Dupont')) }
-    let(:search_term) { nil }
-    let(:order_by) { nil }
-
-    subject { members_helpers.billed_users_for(group, search_term, order_by: order_by) }
-
-    context 'when a search parameter is present' do
-      let(:search_term) { 'John' }
-
-      context 'when a sorting parameter is provided (eg name descending)' do
-        let(:order_by) { 'name_desc' }
-
-        it 'sorts results accordingly' do
-          expect(subject).to eq([john_smith, john_doe].map(&:user))
-        end
-      end
-
-      context 'when a sorting parameter is not provided' do
-        let(:order_by) { nil }
-
-        it 'sorts results by name ascending' do
-          expect(subject).to eq([john_doe, john_smith].map(&:user))
-        end
-      end
-    end
-
-    context 'when a search parameter is not present' do
-      subject { members_helpers.billed_users_for(group, search_term) }
-
-      it 'returns expected users in name asc order' do
-        allow(group).to receive(:billed_user_members).and_return([john_doe, john_smith, sophie, maria])
-
-        expect(subject).to eq([john_doe, john_smith, maria, sophie].map(&:user))
-      end
-
-      context 'and when a sorting parameter is provided (eg name descending)' do
-        let(:order_by) { 'name_desc' }
-
-        subject { members_helpers.billed_users_for(group, search_term, order_by: order_by) }
-
-        it 'sorts results accordingly' do
-          expect(subject).to eq([sophie, maria, john_smith, john_doe].map(&:user))
-        end
-      end
-    end
-  end
 end

ee/spec/requests/api/members_spec.rb

@@ -399,6 +399,16 @@ RSpec.describe API::Members do
         expect_paginated_array_response(*[owner, maintainer, nested_user, project_user, linked_group_user].map(&:id))
       end
 
+      context 'when the current user does not have the :admin_group_member ability' do
+        it 'is a bad request' do
+          not_an_owner = create(:user)
+
+          get api(url, not_an_owner), params: params
+
+          expect(response).to have_gitlab_http_status(:bad_request)
+        end
+      end
+
       context 'with seach params provided' do
         let(:params) { { search: nested_user.name } }