Migration from notifications to mailboxer

app/models/notification.rb

@@ -24,4 +24,35 @@ class Notification < ApplicationRecord
   def send_message
     sender.send_message(recipient, body, subject)
   end
+
+  def migrate_to_mailboxer!
+    conversation = Mailboxer::ConversationBuilder.new(
+      subject:    subject,
+      created_at: created_at,
+      updated_at: updated_at
+    ).build
+
+    message = Mailboxer::MessageBuilder.new(
+      sender:       sender,
+      conversation: conversation,
+      recipients:   [recipient],
+      body:         body,
+      subject:      subject,
+      # attachment:   attachment,
+      created_at:   created_at,
+      updated_at:   updated_at
+    ).build
+
+    notification = Mailboxer::NotificationBuilder.new(
+      recipients: [recipient],
+      subject:    subject,
+      body:       body,
+      sender:     sender
+    ).build
+
+    conversation.save!
+    message.save!
+    notification.save!
+    notification.deliver(false, false)
+  end
 end

db/migrate/20190720000625_notifications_to_mailboxer.rb

@@ -1,27 +1,10 @@
 class NotificationsToMailboxer < ActiveRecord::Migration[5.2]
   def up
-    Notification.all.each do |n|
-      next unless n.valid?
-
-      conversation = Mailboxer::ConversationBuilder.new(
-        subject:    n.subject,
-        created_at: n.created_at,
-        updated_at: n.updated_at
-      ).build
-
-      message = Mailboxer::MessageBuilder.new(
-        sender:       n.sender,
-        conversation: conversation,
-        recipients:   [n.recipient],
-        body:         n.body,
-        subject:      n.subject,
-        # attachment:   attachment,
-        created_at:   n.created_at,
-        updated_at:   n.updated_at
-      ).build
-
-      conversation.save!
-      message.save!
+    Notification.find_in_batches do |group|
+      group.each do |n|
+        next unless n.valid?
+        n.migrate_to_mailboxer!
+      end
     end
   end
 end

spec/models/notification_spec.rb

@@ -3,6 +3,27 @@ require 'rails_helper'
 describe Notification do
   let(:notification) { FactoryBot.create(:notification) }
 
+  describe 'migration to mailboxer' do
+    let(:body) do
+      "Hellos
+      how are you today?
+      I am fine
+
+      -- me
+      "
+    end
+    let(:sender) { FactoryBot.create :member }
+    let(:recipient) { FactoryBot.create :member }
+    let(:notification) do
+      FactoryBot.create :notification,
+        subject: 'hello', body: body,
+        sender: sender,
+        recipient: recipient
+    end
+    before { notification.migrate_to_mailboxer! }
+    it { expect(recipient.mailbox.inbox.count).to eq 1 }
+    it { expect(recipient.mailbox.inbox.first.subject).to eq 'hello' }
+  end
   it "belongs to a post" do
     expect(notification.post).to be_an_instance_of Post
   end