Add specs

app/models/merge_request_diff.rb

@@ -134,6 +134,18 @@ class MergeRequestDiff < ActiveRecord::Base
     st_commits.map { |commit| commit[:id] }
   end
+  def diff_refs=(new_diff_refs)
+    if new_diff_refs
+      self.base_commit_sha = new_diff_refs.base_sha
+      self.start_commit_sha = new_diff_refs.start_sha
+      self.head_commit_sha = new_diff_refs.head_sha
+    else
+      self.base_commit_sha = nil
+      self.start_commit_sha = nil
+      self.head_commit_sha = nil
+    end
+  end
+
   def diff_refs
     return unless start_commit_sha || base_commit_sha

spec/factories/notes.rb

@@ -40,6 +40,7 @@ FactoryGirl.define do
       transient do
         line_number 14
+        diff_refs { noteable.try(:diff_refs) }
       end
       position do
@@ -48,7 +49,7 @@ FactoryGirl.define do
           new_path: "files/ruby/popen.rb",
           old_line: nil,
           new_line: line_number,
-          diff_refs: noteable.try(:diff_refs)
+          diff_refs: diff_refs
         )
       end

spec/features/merge_requests/discussion_spec.rb

+require 'spec_helper'
+
+feature 'Merge Request Discussions', feature: true do
+  before do
+    login_as :admin
+  end
+
+  context "Diff discussions" do
+    let(:merge_request) { create(:merge_request, importing: true) }
+    let(:project) { merge_request.source_project }
+    let!(:old_merge_request_diff) { merge_request.merge_request_diffs.create(diff_refs: outdated_diff_refs) }
+    let!(:new_merge_request_diff) { merge_request.merge_request_diffs.create }
+
+    let!(:outdated_discussion) { create(:diff_note_on_merge_request, project: project, noteable: merge_request, position: outdated_position).to_discussion }
+    let!(:active_discussion) { create(:diff_note_on_merge_request, noteable: merge_request, project: project).to_discussion }
+
+    let(:outdated_position) do
+      Gitlab::Diff::Position.new(
+        old_path: "files/ruby/popen.rb",
+        new_path: "files/ruby/popen.rb",
+        old_line: nil,
+        new_line: 9,
+        diff_refs: outdated_diff_refs
+      )
+    end
+
+    let(:outdated_diff_refs) { project.commit("874797c3a73b60d2187ed6e2fcabd289ff75171e").diff_refs }
+
+    before(:each) do
+      visit namespace_project_merge_request_path(project.namespace, project, merge_request)
+    end
+
+    context 'active discussions' do
+      it 'shows a link to the diff' do
+        within(".discussion[data-discussion-id='#{active_discussion.id}']") do
+          path = diffs_namespace_project_merge_request_path(project.namespace, project, merge_request, anchor: active_discussion.line_code)
+          expect(page).to have_link('the diff', href: path)
+        end
+      end
+    end
+
+    context 'outdated discussions' do
+      it 'shows a link to the outdated diff' do
+        within(".discussion[data-discussion-id='#{outdated_discussion.id}']") do
+          path = diffs_namespace_project_merge_request_path(project.namespace, project, merge_request, diff_id: old_merge_request_diff.id, anchor: outdated_discussion.line_code)
+          expect(page).to have_link('an outdated diff', href: path)
+        end
+      end
+    end
+  end
+end

spec/features/merge_requests/merge_request_versions_spec.rb → spec/features/merge_requests/versions_spec.rb

@@ -36,9 +36,24 @@ feature 'Merge Request versions', js: true, feature: true do
       expect(page).to have_content '5 changed files'
     end
-    it 'show the message about disabled comments' do
+    it 'show the message about disabled comment creation' do
       expect(page).to have_content 'comment creation is disabled'
     end
+
+    it 'shows comments that were last relevant at that version' do
+      position = Gitlab::Diff::Position.new(
+        old_path: ".gitmodules",
+        new_path: ".gitmodules",
+        old_line: nil,
+        new_line: 4,
+        diff_refs: merge_request_diff1.diff_refs
+      )
+      outdated_diff_note = create(:diff_note_on_merge_request, project: project, noteable: merge_request, position: position)
+      outdated_diff_note.position = outdated_diff_note.original_position
+      outdated_diff_note.save!
+
+      expect(page).to have_css(".diffs .notes[data-discussion-id='#{outdated_diff_note.discussion_id}']")
+    end
   end
   describe 'compare with older version' do

spec/models/diff_note_spec.rb

@@ -155,6 +155,23 @@ describe DiffNote, models: true do
     end
   end
+  describe '#latest_merge_request_diff' do
+    context 'when active' do
+      it 'returns the current merge request diff' do
+        expect(subject.latest_merge_request_diff).to eq(merge_request.merge_request_diff)
+      end
+    end
+
+    context 'when outdated' do
+      let!(:old_merge_request_diff) { merge_request.merge_request_diff }
+      let!(:new_merge_request_diff) { merge_request.merge_request_diffs.create(diff_refs: commit.diff_refs) }
+
+      it 'returns the latest merge request diff that this diff note applied to' do
+        expect(subject.latest_merge_request_diff).to eq(old_merge_request_diff)
+      end
+    end
+  end
+
   describe "creation" do
     describe "updating of position" do
       context "when noteable is a commit" do