add a spec for RemoveApprovalService

spec/services/merge_requests/remove_approval_service_spec.rb

+require 'rails_helper'
+
+describe MergeRequests::RemoveApprovalService, services: true do
+  describe '#execute' do
+    let(:user) { create(:user) }
+    let(:merge_request) { create(:merge_request) }
+    let(:project) { merge_request.project }
+
+    subject(:service) { described_class.new(project, user) }
+
+    def execute!
+      service.execute(merge_request)
+    end
+
+    context 'with a user who has approved' do
+      before do
+        merge_request.approvals.create(user: user)
+      end
+
+      it 'removes the approval' do
+        expect(merge_request.approvals.size).to eq 1
+        execute!
+        expect(merge_request.approvals).to be_empty
+      end
+
+      it 'creates an unapproval note' do
+        expect(SystemNoteService).to receive(:unapprove_mr)
+
+        execute!
+      end
+
+      it 'does not send a notification' do
+        expect(Notify).not_to receive(:unapprove_mr)
+
+        execute!
+      end
+    end
+
+    context 'with an approved merge request' do
+      let(:notify) { Object.new }
+
+      before do
+        merge_request.update_attribute :approvals_before_merge, 1
+        merge_request.approvals.create(user: user)
+        allow(service).to receive(:notification_service).and_return(notify)
+      end
+
+      it 'sends a notification' do
+        expect(notify).to receive(:unapprove_mr)
+        execute!
+      end
+    end
+  end
+end