Merge branch '38096-splitmr-write-resource-milestone-events-pd' into 'master'

Create ResourceMilestoneEvents whenever milestones are changed

See merge request gitlab-org/gitlab!24780

app/models/concerns/milestone_eventable.rb

+# frozen_string_literal: true
+
+module MilestoneEventable
+  extend ActiveSupport::Concern
+
+  included do
+    has_many :resource_milestone_events
+  end
+end

app/models/concerns/resource_event_tools.rb

+# frozen_string_literal: true
+
+module ResourceEventTools
+  extend ActiveSupport::Concern
+
+  included do
+    belongs_to :user
+
+    validates :user, presence: { unless: :importing? }, on: :create
+
+    validate :exactly_one_issuable
+
+    scope :created_after, ->(time) { where('created_at > ?', time) }
+  end
+
+  def exactly_one_issuable
+    issuable_count = self.class.issuable_attrs.count { |attr| self["#{attr}_id"] }
+
+    return true if issuable_count == 1
+
+    # if none of issuable IDs is set, check explicitly if nested issuable
+    # object is set, this is used during project import
+    if issuable_count == 0 && importing?
+      issuable_count = self.class.issuable_attrs.count { |attr| self.public_send(attr) } # rubocop:disable GitlabSecurity/PublicSend
+
+      return true if issuable_count == 1
+    end
+
+    errors.add(:base, "Exactly one of #{self.class.issuable_attrs.join(', ')} is required")
+  end
+end

app/models/issue.rb

@@ -15,6 +15,7 @@ class Issue < ApplicationRecord
   include ThrottledTouch
   include LabelEventable
   include IgnorableColumns
+  include MilestoneEventable
 
   DueDateStruct                   = Struct.new(:title, :name).freeze
   NoDueDate                       = DueDateStruct.new('No Due Date', '0').freeze

app/models/merge_request.rb

@@ -18,6 +18,7 @@ class MergeRequest < ApplicationRecord
   include DeprecatedAssignee
   include ShaAttribute
   include IgnorableColumns
+  include MilestoneEventable
 
   sha_attribute :squash_commit_sha
 

app/models/milestone_note.rb

+# frozen_string_literal: true
+
+class MilestoneNote < ::Note
+  attr_accessor :resource_parent, :event, :milestone
+
+  def self.from_event(event, resource: nil, resource_parent: nil)
+    resource ||= event.resource
+
+    attrs = {
+        system: true,
+        author: event.user,
+        created_at: event.created_at,
+        noteable: resource,
+        milestone: event.milestone,
+        event: event,
+        system_note_metadata: ::SystemNoteMetadata.new(action: 'milestone'),
+        resource_parent: resource_parent
+    }
+
+    if resource_parent.is_a?(Project)
+      attrs[:project_id] = resource_parent.id
+    end
+
+    MilestoneNote.new(attrs)
+  end
+
+  def note
+    @note ||= note_text
+  end
+
+  def note_html
+    @note_html ||= Banzai::Renderer.cacheless_render_field(self, :note, { group: group, project: project })
+  end
+
+  def project
+    resource_parent if resource_parent.is_a?(Project)
+  end
+
+  def group
+    resource_parent if resource_parent.is_a?(Group)
+  end
+
+  private
+
+  def note_text(html: false)
+    format = milestone&.group_milestone? ? :name : :iid
+    milestone.nil? ? 'removed milestone' : "changed milestone to #{milestone.to_reference(project, format: format)}"
+  end
+end

app/models/resource_label_event.rb

@@ -4,20 +4,17 @@ class ResourceLabelEvent < ApplicationRecord
   include Importable
   include Gitlab::Utils::StrongMemoize
   include CacheMarkdownField
+  include ResourceEventTools
 
   cache_markdown_field :reference
 
-  belongs_to :user
   belongs_to :issue
   belongs_to :merge_request
   belongs_to :label
 
-  scope :created_after, ->(time) { where('created_at > ?', time) }
   scope :inc_relations, -> { includes(:label, :user) }
 
-  validates :user, presence: { unless: :importing? }, on: :create
   validates :label, presence: { unless: :importing? }, on: :create
-  validate :exactly_one_issuable
 
   after_save :expire_etag_cache
   after_destroy :expire_etag_cache
@@ -94,22 +91,6 @@ class ResourceLabelEvent < ApplicationRecord
     end
   end
 
-  def exactly_one_issuable
-    issuable_count = self.class.issuable_attrs.count { |attr| self["#{attr}_id"] }
-
-    return true if issuable_count == 1
-
-    # if none of issuable IDs is set, check explicitly if nested issuable
-    # object is set, this is used during project import
-    if issuable_count == 0 && importing?
-      issuable_count = self.class.issuable_attrs.count { |attr| self.public_send(attr) } # rubocop:disable GitlabSecurity/PublicSend
-
-      return true if issuable_count == 1
-    end
-
-    errors.add(:base, "Exactly one of #{self.class.issuable_attrs.join(', ')} is required")
-  end
-
   def expire_etag_cache
     issuable.expire_note_etag_cache
   end

app/models/resource_milestone_event.rb

+# frozen_string_literal: true
+
+class ResourceMilestoneEvent < ApplicationRecord
+  include Gitlab::Utils::StrongMemoize
+  include Importable
+  include ResourceEventTools
+
+  belongs_to :issue
+  belongs_to :merge_request
+  belongs_to :milestone
+
+  scope :by_issue, ->(issue) { where(issue_id: issue.id) }
+  scope :by_merge_request, ->(merge_request) { where(merge_request_id: merge_request.id) }
+
+  enum action: {
+         add: 1,
+         remove: 2
+       }
+
+  # state is used for issue and merge request states.
+  enum state: Issue.available_states.merge(MergeRequest.available_states)
+
+  def self.issuable_attrs
+    %i(issue merge_request).freeze
+  end
+
+  def resource
+    issue || merge_request
+  end
+end

app/services/issuable/clone/attributes_rewriter.rb

@@ -19,6 +19,7 @@ module Issuable
 
         copy_resource_label_events
         copy_resource_weight_events
+        copy_resource_milestone_events
       end
 
       private
@@ -65,6 +66,23 @@ module Issuable
         end
       end
 
+      def copy_resource_milestone_events
+        entity_key = new_entity.class.name.underscore.foreign_key
+
+        copy_events(ResourceMilestoneEvent.table_name, original_entity.resource_milestone_events) do |event|
+          matching_destination_milestone = matching_milestone(event.milestone.title)
+
+          if matching_destination_milestone.present?
+            event.attributes
+              .except('id', 'reference', 'reference_html')
+              .merge(entity_key => new_entity.id,
+                     'milestone_id' => matching_destination_milestone.id,
+                     'action' => ResourceMilestoneEvent.actions[event.action],
+                     'state' => ResourceMilestoneEvent.states[event.state])
+          end
+        end
+      end
+
       def copy_events(table_name, events_to_copy)
         events_to_copy.find_in_batches do |batch|
           events = batch.map do |event|

app/services/issuable/common_system_notes_service.rb

@@ -22,13 +22,17 @@ module Issuable
         end
 
         create_due_date_note if issuable.previous_changes.include?('due_date')
-        create_milestone_note if issuable.previous_changes.include?('milestone_id')
+        create_milestone_note if has_milestone_changes?
         create_labels_note(old_labels) if old_labels && issuable.labels != old_labels
       end
     end
 
     private
 
+    def has_milestone_changes?
+      issuable.previous_changes.include?('milestone_id')
+    end
+
     def handle_time_tracking_note
       if issuable.previous_changes.include?('time_estimate')
         create_time_estimate_note
@@ -95,7 +99,16 @@ module Issuable
     end
 
     def create_milestone_note
-      SystemNoteService.change_milestone(issuable, issuable.project, current_user, issuable.milestone)
+      if milestone_changes_tracking_enabled?
+        # Creates a synthetic note
+        ResourceEvents::ChangeMilestoneService.new(resource: issuable, user: current_user).execute
+      else
+        SystemNoteService.change_milestone(issuable, issuable.project, current_user, issuable.milestone)
+      end
+    end
+
+    def milestone_changes_tracking_enabled?
+      ::Feature.enabled?(:track_resource_milestone_change_events, issuable.project)
     end
 
     def create_due_date_note

app/services/resource_events/change_milestone_service.rb

+# frozen_string_literal: true
+
+module ResourceEvents
+  class ChangeMilestoneService
+    attr_reader :resource, :user, :event_created_at, :resource_args
+
+    def initialize(resource:, user:, created_at: Time.now)
+      @resource = resource
+      @user = user
+      @event_created_at = created_at
+
+      @resource_args = {
+        user_id: user.id,
+        created_at: event_created_at
+      }
+    end
+
+    def execute
+      args = build_resource_args
+
+      action = if milestone.nil?
+                 :remove
+               else
+                 :add
+               end
+
+      record = args.merge(milestone_id: milestone&.id, action: ResourceMilestoneEvent.actions[action])
+
+      create_event(record)
+    end
+
+    private
+
+    def milestone
+      resource&.milestone
+    end
+
+    def create_event(record)
+      ResourceMilestoneEvent.create(record)
+
+      resource.expire_note_etag_cache
+    end
+
+    def build_resource_args
+      key = resource.class.name.underscore.foreign_key
+
+      resource_args.merge(key => resource.id, state: ResourceMilestoneEvent.states[resource.state])
+    end
+  end
+end

app/services/resource_events/merge_into_notes_service.rb

@@ -9,6 +9,11 @@ module ResourceEvents
   class MergeIntoNotesService
     include Gitlab::Utils::StrongMemoize
 
+    SYNTHETIC_NOTE_BUILDER_SERVICES = [
+      SyntheticLabelNotesBuilderService,
+      SyntheticMilestoneNotesBuilderService
+    ].freeze
+
     attr_reader :resource, :current_user, :params
 
     def initialize(resource, current_user, params = {})
@@ -24,7 +29,9 @@ module ResourceEvents
     private
 
     def synthetic_notes
-      SyntheticLabelNotesBuilderService.new(resource, current_user, params).execute
+      SYNTHETIC_NOTE_BUILDER_SERVICES.flat_map do |service|
+        service.new(resource, current_user, params).execute
+      end
     end
   end
 end

app/services/resource_events/synthetic_milestone_notes_builder_service.rb

+# frozen_string_literal: true
+
+# We store events about resource milestone changes in a separate table,
+# but we still want to display notes about milestone changes
+# as classic system notes in UI. This service generates "synthetic" notes for
+# milestone event changes.
+
+module ResourceEvents
+  class SyntheticMilestoneNotesBuilderService < BaseSyntheticNotesBuilderService
+    private
+
+    def synthetic_notes
+      return [] unless tracking_enabled?
+
+      milestone_change_events.map do |event|
+        MilestoneNote.from_event(event, resource: resource, resource_parent: resource_parent)
+      end
+    end
+
+    def milestone_change_events
+      return [] unless resource.respond_to?(:resource_milestone_events)
+
+      events = resource.resource_milestone_events.includes(user: :status) # rubocop: disable CodeReuse/ActiveRecord
+      since_fetch_at(events)
+    end
+
+    def tracking_enabled?
+      ::Feature.enabled?(:track_resource_milestone_change_events, resource.project)
+    end
+  end
+end

changelogs/unreleased/38096-splitmr-write-resource-milestone-events-pd.yml

+---
+title: Add possibility to track milestone changes on issues and merge requests
+merge_request: 24780
+author:
+type: added

ee/spec/features/issues/form_spec.rb

@@ -34,7 +34,7 @@ describe 'New/edit issue', :js do
       before do
         # Using `allow_any_instance_of`/`and_wrap_original`, `original` would
         # somehow refer to the very block we defined to _wrap_ that method, instead of
-        # the original method, resulting in infinite recurison when called.
+        # the original method, resulting in infinite recursion when called.
         # This is likely a bug with helper modules included into dynamically generated view classes.
         # To work around this, we have to hold on to and call to the original implementation manually.
         original_issue_dropdown_options = FormHelper.instance_method(:assignees_dropdown_options)

spec/controllers/projects/milestones_controller_spec.rb

@@ -135,6 +135,10 @@ describe Projects::MilestonesController do
   end
 
   describe "#destroy" do
+    before do
+      stub_feature_flags(track_resource_milestone_change_events: false)
+    end
+
     it "removes milestone" do
       expect(issue.milestone_id).to eq(milestone.id)
 

spec/factories/resource_milestone_event.rb

+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :resource_milestone_event do
+    issue { merge_request.nil? ? create(:issue) : nil }
+    merge_request { nil }
+    milestone
+    action { :add }
+    state { :opened }
+    user { issue&.author || merge_request&.author || create(:user) }
+  end
+end

spec/lib/gitlab/import_export/all_models.yml

@@ -9,6 +9,7 @@ issues:
 - notes
 - resource_label_events
 - resource_weight_events
+- resource_milestone_events
 - sentry_issue
 - label_links
 - labels
@@ -109,6 +110,7 @@ merge_requests:
 - milestone
 - notes
 - resource_label_events
+- resource_milestone_events
 - label_links
 - labels
 - last_edited_by

spec/models/milestone_note_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe MilestoneNote do
+  describe '.from_event' do
+    let(:author) { create(:user) }
+    let(:project) { create(:project, :repository) }
+    let(:noteable) { create(:issue, author: author, project: project) }
+    let(:event) { create(:resource_milestone_event, issue: noteable) }
+
+    subject { described_class.from_event(event, resource: noteable, resource_parent: project) }
+
+    it_behaves_like 'a system note', exclude_project: true do
+      let(:action) { 'milestone' }
+    end
+  end
+end

spec/models/resource_milestone_event_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe ResourceMilestoneEvent, type: :model do
+  it_behaves_like 'a resource event'
+  it_behaves_like 'a resource event for issues'
+  it_behaves_like 'a resource event for merge requests'
+
+  it_behaves_like 'having unique enum values'
+
+  describe 'associations' do
+    it { is_expected.to belong_to(:milestone) }
+  end
+
+  describe 'validations' do
+    context 'when issue and merge_request are both nil' do
+      subject { build(described_class.name.underscore.to_sym, issue: nil, merge_request: nil) }
+
+      it { is_expected.not_to be_valid }
+    end
+
+    context 'when issue and merge_request are both set' do
+      subject { build(described_class.name.underscore.to_sym, issue: build(:issue), merge_request: build(:merge_request)) }
+
+      it { is_expected.not_to be_valid }
+    end
+
+    context 'when issue is set' do
+      subject { create(described_class.name.underscore.to_sym, issue: create(:issue), merge_request: nil) }
+
+      it { is_expected.to be_valid }
+    end
+
+    context 'when merge_request is set' do
+      subject { create(described_class.name.underscore.to_sym, issue: nil, merge_request: create(:merge_request)) }
+
+      it { is_expected.to be_valid }
+    end
+  end
+
+  describe 'states' do
+    [Issue, MergeRequest].each do |klass|
+      klass.available_states.each do |state|
+        it "supports state #{state.first} for #{klass.name.underscore}" do
+          model = create(klass.name.underscore, state: state[0])
+          key = model.class.name.underscore
+          event = build(described_class.name.underscore.to_sym, key => model, state: model.state)
+
+          expect(event.state).to eq(state[0])
+        end
+      end
+    end
+  end
+end

spec/services/issuable/clone/attributes_rewriter_spec.rb

@@ -75,5 +75,47 @@ describe Issuable::Clone::AttributesRewriter do
 
       expect(new_issue.reload.milestone).to eq(milestone)
     end
+
+    context 'with existing milestone events' do
+      let!(:milestone1_project1) { create(:milestone, title: 'milestone1', project: project1) }
+      let!(:milestone2_project1) { create(:milestone, title: 'milestone2', project: project1) }
+      let!(:milestone3_project1) { create(:milestone, title: 'milestone3', project: project1) }
+
+      let!(:milestone1_project2) { create(:milestone, title: 'milestone1', project: project2) }
+      let!(:milestone2_project2) { create(:milestone, title: 'milestone2', project: project2) }
+
+      before do
+        original_issue.update(milestone: milestone2_project1)
+
+        create_event(milestone1_project1)
+        create_event(milestone2_project1)
+        create_event(milestone1_project1, 'remove')
+        create_event(milestone3_project1)
+      end
+
+      it 'copies existing resource milestone events' do
+        subject.execute
+
+        new_issue_milestone_events = new_issue.reload.resource_milestone_events
+        expect(new_issue_milestone_events.count).to eq(3)
+
+        expect_milestone_event(new_issue_milestone_events.first, milestone: milestone1_project2, action: 'add', state: 'opened')
+        expect_milestone_event(new_issue_milestone_events.second, milestone: milestone2_project2, action: 'add', state: 'opened')
+        expect_milestone_event(new_issue_milestone_events.third, milestone: milestone1_project2, action: 'remove', state: 'opened')
+      end
+
+      def create_event(milestone, action = 'add')
+        create(:resource_milestone_event, issue: original_issue, milestone: milestone, action: action)
+      end
+
+      def expect_milestone_event(event, expected_attrs)
+        expect(event.milestone_id).to eq(expected_attrs[:milestone].id)
+        expect(event.action).to eq(expected_attrs[:action])
+        expect(event.state).to eq(expected_attrs[:state])
+
+        expect(event.reference).to be_nil
+        expect(event.reference_html).to be_nil
+      end
+    end
   end
 end

spec/services/issuable/common_system_notes_service_spec.rb

@@ -3,8 +3,9 @@
 require 'spec_helper'
 
 describe Issuable::CommonSystemNotesService do
-  let(:user) { create(:user) }
-  let(:project) { create(:project) }
+  let_it_be(:project) { create(:project) }
+  let_it_be(:user) { create(:user) }
+
   let(:issuable) { create(:issue, project: project) }
 
   context 'on issuable update' do
@@ -35,6 +36,8 @@ describe Issuable::CommonSystemNotesService do
       before do
         milestone = create(:milestone, project: project)
         issuable.milestone_id = milestone.id
+
+        stub_feature_flags(track_resource_milestone_change_events: false)
       end
 
       it_behaves_like 'system note creation', {}, 'changed milestone'
@@ -97,12 +100,39 @@ describe Issuable::CommonSystemNotesService do
       expect(event.user_id).to eq user.id
     end
 
-    it 'creates a system note for milestone set' do
-      issuable.milestone = create(:milestone, project: project)
-      issuable.save
+    context 'when milestone change event tracking is disabled' do
+      before do
+        stub_feature_flags(track_resource_milestone_change_events: false)
 
-      expect { subject }.to change { issuable.notes.count }.from(0).to(1)
-      expect(issuable.notes.last.note).to match('changed milestone')
+        issuable.milestone = create(:milestone, project: project)
+        issuable.save
+      end
+
+      it 'creates a system note for milestone set' do
+        expect { subject }.to change { issuable.notes.count }.from(0).to(1)
+        expect(issuable.notes.last.note).to match('changed milestone')
+      end
+
+      it 'does not create a milestone change event' do
+        expect { subject }.not_to change { ResourceMilestoneEvent.count }
+      end
+    end
+
+    context 'when milestone change event tracking is enabled' do
+      let_it_be(:milestone) { create(:milestone, project: project) }
+      let_it_be(:issuable) { create(:issue, project: project, milestone: milestone) }
+
+      before do
+        stub_feature_flags(track_resource_milestone_change_events: true)
+      end
+
+      it 'does not create a system note for milestone set' do
+        expect { subject }.not_to change { issuable.notes.count }
+      end
+
+      it 'creates a milestone change event' do
+        expect { subject }.to change { ResourceMilestoneEvent.count }.from(0).to(1)
+      end
     end
 
     it 'creates a system note for due_date set' do

spec/services/issues/update_service_spec.rb

@@ -385,6 +385,10 @@ describe Issues::UpdateService, :mailer do
       end
 
       context 'when the milestone is removed' do
+        before do
+          stub_feature_flags(track_resource_milestone_change_events: false)
+        end
+
         let!(:non_subscriber) { create(:user) }
 
         let!(:subscriber) do
@@ -411,6 +415,10 @@ describe Issues::UpdateService, :mailer do
       end
 
       context 'when the milestone is changed' do
+        before do
+          stub_feature_flags(track_resource_milestone_change_events: false)
+        end
+
         let!(:non_subscriber) { create(:user) }
 
         let!(:subscriber) do

spec/services/merge_requests/update_service_spec.rb

@@ -367,6 +367,10 @@ describe MergeRequests::UpdateService, :mailer do
       end
 
       context 'when the milestone is removed' do
+        before do
+          stub_feature_flags(track_resource_milestone_change_events: false)
+        end
+
         let!(:non_subscriber) { create(:user) }
 
         let!(:subscriber) do
@@ -393,6 +397,10 @@ describe MergeRequests::UpdateService, :mailer do
       end
 
       context 'when the milestone is changed' do
+        before do
+          stub_feature_flags(track_resource_milestone_change_events: false)
+        end
+
         let!(:non_subscriber) { create(:user) }
 
         let!(:subscriber) do

spec/services/resource_events/change_milestone_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe ResourceEvents::ChangeMilestoneService do
+  shared_examples 'milestone events creator' do
+    let_it_be(:user) { create(:user) }
+
+    let_it_be(:milestone) { create(:milestone) }
+
+    context 'when milestone is present' do
+      before do
+        resource.milestone = milestone
+      end
+
+      let(:service) { described_class.new(resource: resource, user: user, created_at: created_at_time) }
+
+      it 'creates the expected event record' do
+        expect { service.execute }.to change { ResourceMilestoneEvent.count }.from(0).to(1)
+
+        events = ResourceMilestoneEvent.all
+
+        expect(events.size).to eq(1)
+        expect_event_record(events.first, action: 'add', milestone: milestone, state: 'opened')
+      end
+    end
+
+    context 'when milestones is not present' do
+      before do
+        resource.milestone = nil
+      end
+
+      let(:service) { described_class.new(resource: resource, user: user, created_at: created_at_time) }
+
+      it 'creates the expected event records' do
+        expect { service.execute }.to change { ResourceMilestoneEvent.count }.from(0).to(1)
+
+        expect_event_record(ResourceMilestoneEvent.first, action: 'remove', milestone: nil, state: 'opened')
+      end
+    end
+
+    def expect_event_record(event, expected_attrs)
+      expect(event.action).to eq(expected_attrs[:action])
+      expect(event.state).to eq(expected_attrs[:state])
+      expect(event.user).to eq(user)
+      expect(event.issue).to eq(resource) if resource.is_a?(Issue)
+      expect(event.issue).to be_nil unless resource.is_a?(Issue)
+      expect(event.merge_request).to eq(resource) if resource.is_a?(MergeRequest)
+      expect(event.merge_request).to be_nil unless resource.is_a?(MergeRequest)
+      expect(event.milestone).to eq(expected_attrs[:milestone])
+      expect(event.created_at).to eq(created_at_time)
+    end
+  end
+
+  let_it_be(:merge_request) { create(:merge_request) }
+  let_it_be(:issue) { create(:issue) }
+
+  let!(:created_at_time) { Time.utc(2019, 12, 30) }
+
+  it_behaves_like 'milestone events creator' do
+    let(:resource) { issue }
+  end
+
+  it_behaves_like 'milestone events creator' do
+    let(:resource) { merge_request }
+  end
+end

spec/support/shared_examples/quick_actions/issue/move_quick_action_shared_examples.rb

@@ -50,6 +50,8 @@ RSpec.shared_examples 'move quick action' do
       let(:bug)      { create(:label, project: project, title: 'bug') }
       let(:wontfix)  { create(:label, project: project, title: 'wontfix') }
 
+      let!(:target_milestone) { create(:milestone, title: '1.0', project: target_project) }
+
       before do
         target_project.add_maintainer(user)
       end

spec/support/shared_examples/resource_events.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+shared_examples 'a resource event' do
+  let_it_be(:user1) { create(:user) }
+  let_it_be(:user2) { create(:user) }
+
+  let_it_be(:issue1) { create(:issue, author: user1) }
+  let_it_be(:issue2) { create(:issue, author: user1) }
+  let_it_be(:issue3) { create(:issue, author: user2) }
+
+  describe 'validations' do
+    it { is_expected.not_to allow_value(nil).for(:user) }
+  end
+
+  describe 'associations' do
+    it { is_expected.to belong_to(:user) }
+  end
+
+  describe '.created_after' do
+    let!(:created_at1) { 1.day.ago }
+    let!(:created_at2) { 2.days.ago }
+    let!(:created_at3) { 3.days.ago }
+
+    let!(:event1) { create(described_class.name.underscore.to_sym, issue: issue1, created_at: created_at1) }
+    let!(:event2) { create(described_class.name.underscore.to_sym, issue: issue2, created_at: created_at2) }
+    let!(:event3) { create(described_class.name.underscore.to_sym, issue: issue2, created_at: created_at3) }
+
+    it 'returns the expected events' do
+      events = described_class.created_after(created_at3)
+
+      expect(events).to contain_exactly(event1, event2)
+    end
+
+    it 'returns no events if time is after last record time' do
+      events = described_class.created_after(1.minute.ago)
+
+      expect(events).to be_empty
+    end
+  end
+end
+
+shared_examples 'a resource event for issues' do
+  let_it_be(:user1) { create(:user) }
+  let_it_be(:user2) { create(:user) }
+
+  let_it_be(:issue1) { create(:issue, author: user1) }
+  let_it_be(:issue2) { create(:issue, author: user1) }
+  let_it_be(:issue3) { create(:issue, author: user2) }
+
+  describe 'associations' do
+    it { is_expected.to belong_to(:issue) }
+  end
+
+  describe '.by_issue' do
+    let_it_be(:event1) { create(described_class.name.underscore.to_sym, issue: issue1) }
+    let_it_be(:event2) { create(described_class.name.underscore.to_sym, issue: issue2) }
+    let_it_be(:event3) { create(described_class.name.underscore.to_sym, issue: issue1) }
+
+    it 'returns the expected records for an issue with events' do
+      events = described_class.by_issue(issue1)
+
+      expect(events).to contain_exactly(event1, event3)
+    end
+
+    it 'returns the expected records for an issue with no events' do
+      events = described_class.by_issue(issue3)
+
+      expect(events).to be_empty
+    end
+  end
+end
+
+shared_examples 'a resource event for merge requests' do
+  let_it_be(:user1) { create(:user) }
+  let_it_be(:user2) { create(:user) }
+
+  let_it_be(:merge_request1) { create(:merge_request, author: user1) }
+  let_it_be(:merge_request2) { create(:merge_request, author: user1) }
+  let_it_be(:merge_request3) { create(:merge_request, author: user2) }
+
+  describe 'associations' do
+    it { is_expected.to belong_to(:merge_request) }
+  end
+
+  describe '.by_merge_request' do
+    let_it_be(:event1) { create(described_class.name.underscore.to_sym, merge_request: merge_request1) }
+    let_it_be(:event2) { create(described_class.name.underscore.to_sym, merge_request: merge_request2) }
+    let_it_be(:event3) { create(described_class.name.underscore.to_sym, merge_request: merge_request1) }
+
+    it 'returns the expected records for an issue with events' do
+      events = described_class.by_merge_request(merge_request1)
+
+      expect(events).to contain_exactly(event1, event3)
+    end
+
+    it 'returns the expected records for an issue with no events' do
+      events = described_class.by_merge_request(merge_request3)
+
+      expect(events).to be_empty
+    end
+  end
+end