Merge branch '48817-fix-mr-changes-discussion-navigation' into 'master'

Resolve ""Jump to first/next unresolved discussion" jumps to resolved discussions"

Closes #48817 and #48602

See merge request gitlab-org/gitlab-ce!20434

11 files changed, 412 insertions, 68 deletions

diff --git a/app/assets/javascripts/diffs/components/diff_discussions.vue b/app/assets/javascripts/diffs/components/diff_discussions.vue
index 20483161033..e64d5511d78 100644
--- a/app/assets/javascripts/diffs/components/diff_discussions.vue
+++ b/app/assets/javascripts/diffs/components/diff_discussions.vue
@@ -30,6 +30,7 @@ export default {
           :render-header="false"
           :render-diff-file="false"
           :always-expanded="true"
+          :discussions-by-diff-order="true"
         />
       </ul>
     </div>
diff --git a/app/assets/javascripts/notes/components/discussion_counter.vue b/app/assets/javascripts/notes/components/discussion_counter.vue
index 6385b75e557..ad6e7cf501d 100644
--- a/app/assets/javascripts/notes/components/discussion_counter.vue
+++ b/app/assets/javascripts/notes/components/discussion_counter.vue
@@ -5,19 +5,20 @@ import resolvedSvg from 'icons/_icon_status_success_solid.svg';
 import mrIssueSvg from 'icons/_icon_mr_issue.svg';
 import nextDiscussionSvg from 'icons/_next_discussion.svg';
 import { pluralize } from '../../lib/utils/text_utility';
-import { scrollToElement } from '../../lib/utils/common_utils';
+import discussionNavigation from '../mixins/discussion_navigation';
 import tooltip from '../../vue_shared/directives/tooltip';
 
 export default {
   directives: {
     tooltip,
   },
+  mixins: [discussionNavigation],
   computed: {
     ...mapGetters([
       'getUserData',
       'getNoteableData',
       'discussionCount',
-      'unresolvedDiscussions',
+      'firstUnresolvedDiscussionId',
       'resolvedDiscussionCount',
     ]),
     isLoggedIn() {
@@ -35,11 +36,6 @@ export default {
     resolveAllDiscussionsIssuePath() {
       return this.getNoteableData.create_issue_to_resolve_discussions_path;
     },
-    firstUnresolvedDiscussionId() {
-      const item = this.unresolvedDiscussions[0] || {};
-
-      return item.id;
-    },
   },
   created() {
     this.resolveSvg = resolveSvg;
@@ -50,22 +46,10 @@ export default {
   methods: {
     ...mapActions(['expandDiscussion']),
     jumpToFirstUnresolvedDiscussion() {
-      const discussionId = this.firstUnresolvedDiscussionId;
-      if (!discussionId) {
-        return;
-      }
-
-      const el = document.querySelector(`[data-discussion-id="${discussionId}"]`);
-      const activeTab = window.mrTabs.currentAction;
-
-      if (activeTab === 'commits' || activeTab === 'pipelines') {
-        window.mrTabs.activateTab('show');
-      }
+      const diffTab = window.mrTabs.currentAction === 'diffs';
+      const discussionId = this.firstUnresolvedDiscussionId(diffTab);
 
-      if (el) {
-        this.expandDiscussion({ discussionId });
-        scrollToElement(el);
-      }
+      this.jumpToDiscussion(discussionId);
     },
   },
 };
diff --git a/app/assets/javascripts/notes/components/noteable_discussion.vue b/app/assets/javascripts/notes/components/noteable_discussion.vue
index 2f1a68731c7..0fe1c16854a 100644
--- a/app/assets/javascripts/notes/components/noteable_discussion.vue
+++ b/app/assets/javascripts/notes/components/noteable_discussion.vue
@@ -1,9 +1,8 @@
 <script>
-import _ from 'underscore';
 import { mapActions, mapGetters } from 'vuex';
 import resolveDiscussionsSvg from 'icons/_icon_mr_issue.svg';
 import nextDiscussionsSvg from 'icons/_next_discussion.svg';
-import { convertObjectPropsToCamelCase, scrollToElement } from '~/lib/utils/common_utils';
+import { convertObjectPropsToCamelCase } from '~/lib/utils/common_utils';
 import { truncateSha } from '~/lib/utils/text_utility';
 import systemNote from '~/vue_shared/components/notes/system_note.vue';
 import { s__ } from '~/locale';
@@ -21,6 +20,7 @@ import placeholderSystemNote from '../../vue_shared/components/notes/placeholder
 import autosave from '../mixins/autosave';
 import noteable from '../mixins/noteable';
 import resolvable from '../mixins/resolvable';
+import discussionNavigation from '../mixins/discussion_navigation';
 import tooltip from '../../vue_shared/directives/tooltip';
 
 export default {
@@ -40,7 +40,7 @@ export default {
   directives: {
     tooltip,
   },
-  mixins: [autosave, noteable, resolvable],
+  mixins: [autosave, noteable, resolvable, discussionNavigation],
   props: {
     discussion: {
       type: Object,
@@ -61,6 +61,11 @@ export default {
       required: false,
       default: false,
     },
+    discussionsByDiffOrder: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
   },
   data() {
     return {
@@ -75,7 +80,12 @@ export default {
       'discussionCount',
       'resolvedDiscussionCount',
       'allDiscussions',
+      'unresolvedDiscussionsIdsByDiff',
+      'unresolvedDiscussionsIdsByDate',
       'unresolvedDiscussions',
+      'unresolvedDiscussionsIdsOrdered',
+      'nextUnresolvedDiscussionId',
+      'isLastUnresolvedDiscussion',
     ]),
     transformedDiscussion() {
       return {
@@ -126,6 +136,10 @@ export default {
     hasMultipleUnresolvedDiscussions() {
       return this.unresolvedDiscussions.length > 1;
     },
+    showJumpToNextDiscussion() {
+      return this.hasMultipleUnresolvedDiscussions &&
+        !this.isLastUnresolvedDiscussion(this.discussion.id, this.discussionsByDiffOrder);
+    },
     shouldRenderDiffs() {
       const { diffDiscussion, diffFile } = this.transformedDiscussion;
 
@@ -242,21 +256,10 @@ Please check your network connection and try again.`;
         });
     },
     jumpToNextDiscussion() {
-      const discussionIds = this.allDiscussions.map(d => d.id);
-      const unresolvedIds = this.unresolvedDiscussions.map(d => d.id);
-      const currentIndex = discussionIds.indexOf(this.discussion.id);
-      const remainingAfterCurrent = discussionIds.slice(currentIndex + 1);
-      const nextIndex = _.findIndex(remainingAfterCurrent, id => unresolvedIds.indexOf(id) > -1);
-
-      if (nextIndex > -1) {
-        const nextId = remainingAfterCurrent[nextIndex];
-        const el = document.querySelector(`[data-discussion-id="${nextId}"]`);
+      const nextId =
+        this.nextUnresolvedDiscussionId(this.discussion.id, this.discussionsByDiffOrder);
 
-        if (el) {
-          this.expandDiscussion({ discussionId: nextId });
-          scrollToElement(el);
-        }
-      }
+      this.jumpToDiscussion(nextId);
     },
   },
 };
@@ -398,7 +401,7 @@ Please check your network connection and try again.`;
                           </a>
                         </div>
                         <div
-                          v-if="hasMultipleUnresolvedDiscussions"
+                          v-if="showJumpToNextDiscussion"
                           class="btn-group"
                           role="group">
                           <button
diff --git a/app/assets/javascripts/notes/mixins/discussion_navigation.js b/app/assets/javascripts/notes/mixins/discussion_navigation.js
new file mode 100644
index 00000000000..f7c4deee1f8
--- /dev/null
+++ b/app/assets/javascripts/notes/mixins/discussion_navigation.js
@@ -0,0 +1,29 @@
+import { scrollToElement } from '~/lib/utils/common_utils';
+
+export default {
+  methods: {
+    jumpToDiscussion(id) {
+      if (id) {
+        const activeTab = window.mrTabs.currentAction;
+        const selector =
+          activeTab === 'diffs'
+            ? `ul.notes[data-discussion-id="${id}"]`
+            : `div.discussion[data-discussion-id="${id}"]`;
+        const el = document.querySelector(selector);
+
+        if (activeTab === 'commits' || activeTab === 'pipelines') {
+          window.mrTabs.activateTab('show');
+        }
+
+        if (el) {
+          this.expandDiscussion({ discussionId: id });
+
+          scrollToElement(el);
+          return true;
+        }
+      }
+
+      return false;
+    },
+  },
+};
diff --git a/app/assets/javascripts/notes/stores/getters.js b/app/assets/javascripts/notes/stores/getters.js
index e9e95dd4219..0d8d197bf71 100644
--- a/app/assets/javascripts/notes/stores/getters.js
+++ b/app/assets/javascripts/notes/stores/getters.js
@@ -70,6 +70,9 @@ export const allDiscussions = (state, getters) => {
   return Object.values(resolved).concat(unresolved);
 };
 
+export const allResolvableDiscussions = (state, getters) =>
+  getters.allDiscussions.filter(d => !d.individual_note && d.resolvable);
+
 export const resolvedDiscussionsById = state => {
   const map = {};
 
@@ -86,6 +89,51 @@ export const resolvedDiscussionsById = state => {
   return map;
 };
 
+// Gets Discussions IDs ordered by the date of their initial note
+export const unresolvedDiscussionsIdsByDate = (state, getters) =>
+  getters.allResolvableDiscussions
+    .filter(d => !d.resolved)
+    .sort((a, b) => {
+      const aDate = new Date(a.notes[0].created_at);
+      const bDate = new Date(b.notes[0].created_at);
+
+      if (aDate < bDate) {
+        return -1;
+      }
+
+      return aDate === bDate ? 0 : 1;
+    })
+    .map(d => d.id);
+
+// Gets Discussions IDs ordered by their position in the diff
+//
+// Sorts the array of resolvable yet unresolved discussions by
+// comparing file names first. If file names are the same, compares
+// line numbers.
+export const unresolvedDiscussionsIdsByDiff = (state, getters) =>
+  getters.allResolvableDiscussions
+    .filter(d => !d.resolved)
+    .sort((a, b) => {
+      if (!a.diff_file || !b.diff_file) {
+        return 0;
+      }
+
+      // Get file names comparison result
+      const filenameComparison = a.diff_file.file_path.localeCompare(b.diff_file.file_path);
+
+      // Get the line numbers, to compare within the same file
+      const aLines = [a.position.formatter.new_line, a.position.formatter.old_line];
+      const bLines = [b.position.formatter.new_line, b.position.formatter.old_line];
+
+      return filenameComparison < 0 ||
+        (filenameComparison === 0 &&
+          // .max() because one of them might be zero (if removed/added)
+          Math.max(aLines[0], aLines[1]) < Math.max(bLines[0], bLines[1]))
+        ? -1
+        : 1;
+    })
+    .map(d => d.id);
+
 export const resolvedDiscussionCount = (state, getters) => {
   const resolvedMap = getters.resolvedDiscussionsById;
 
@@ -102,5 +150,42 @@ export const discussionTabCounter = state => {
   return all.length;
 };
 
+// Returns the list of discussion IDs ordered according to given parameter
+// @param {Boolean} diffOrder - is ordered by diff?
+export const unresolvedDiscussionsIdsOrdered = (state, getters) => diffOrder => {
+  if (diffOrder) {
+    return getters.unresolvedDiscussionsIdsByDiff;
+  }
+  return getters.unresolvedDiscussionsIdsByDate;
+};
+
+// Checks if a given discussion is the last in the current order (diff or date)
+// @param {Boolean} discussionId - id of the discussion
+// @param {Boolean} diffOrder - is ordered by diff?
+export const isLastUnresolvedDiscussion = (state, getters) => (discussionId, diffOrder) => {
+  const idsOrdered = getters.unresolvedDiscussionsIdsOrdered(diffOrder);
+  const lastDiscussionId = idsOrdered[idsOrdered.length - 1];
+
+  return lastDiscussionId === discussionId;
+};
+
+// Gets the ID of the discussion following the one provided, respecting order (diff or date)
+// @param {Boolean} discussionId - id of the current discussion
+// @param {Boolean} diffOrder - is ordered by diff?
+export const nextUnresolvedDiscussionId = (state, getters) => (discussionId, diffOrder) => {
+  const idsOrdered = getters.unresolvedDiscussionsIdsOrdered(diffOrder);
+  const currentIndex = idsOrdered.indexOf(discussionId);
+
+  return idsOrdered.slice(currentIndex + 1, currentIndex + 2)[0];
+};
+
+// @param {Boolean} diffOrder - is ordered by diff?
+export const firstUnresolvedDiscussionId = (state, getters) => diffOrder => {
+  if (diffOrder) {
+    return getters.unresolvedDiscussionsIdsByDiff[0];
+  }
+  return getters.unresolvedDiscussionsIdsByDate[0];
+};
+
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
 export default () => {};
diff --git a/changelogs/unreleased/48817-fix-mr-changes-discussion-navigation.yml b/changelogs/unreleased/48817-fix-mr-changes-discussion-navigation.yml
new file mode 100644
index 00000000000..ec4b843b863
--- /dev/null
+++ b/changelogs/unreleased/48817-fix-mr-changes-discussion-navigation.yml
@@ -0,0 +1,5 @@
+---
+title: Fix navigation to First and Next discussion on MR Changes tab
+merge_request: 20434
+author:
+type: fixed
diff --git a/spec/features/merge_request/user_resolves_diff_notes_and_discussions_resolve_spec.rb b/spec/features/merge_request/user_resolves_diff_notes_and_discussions_resolve_spec.rb
index a0b9d6cb059..1c7aa674955 100644
--- a/spec/features/merge_request/user_resolves_diff_notes_and_discussions_resolve_spec.rb
+++ b/spec/features/merge_request/user_resolves_diff_notes_and_discussions_resolve_spec.rb
@@ -342,8 +342,9 @@ describe 'Merge request > User resolves diff notes and discussions', :js do
         end
       end
 
-      it 'shows jump to next discussion button' do
-        expect(page.all('.discussion-reply-holder', count: 2)).to all(have_selector('.discussion-next-btn'))
+      it 'shows jump to next discussion button, apart from the last one' do
+        expect(page).to have_selector('.discussion-reply-holder', count: 2)
+        expect(page).to have_selector('.discussion-reply-holder .discussion-next-btn', count: 1)
       end
 
       it 'displays next discussion even if hidden' do
diff --git a/spec/javascripts/notes/components/discussion_counter_spec.js b/spec/javascripts/notes/components/discussion_counter_spec.js
index a3869cc6498..d09bc5037ef 100644
--- a/spec/javascripts/notes/components/discussion_counter_spec.js
+++ b/spec/javascripts/notes/components/discussion_counter_spec.js
@@ -46,7 +46,7 @@ describe('DiscussionCounter component', () => {
           discussions,
         });
         setFixtures(`
-          <div data-discussion-id="${firstDiscussionId}"></div>
+          <div class="discussion" data-discussion-id="${firstDiscussionId}"></div>
         `);
 
         vm.jumpToFirstUnresolvedDiscussion();
diff --git a/spec/javascripts/notes/components/noteable_discussion_spec.js b/spec/javascripts/notes/components/noteable_discussion_spec.js
index f3f50aed232..2a01bd85520 100644
--- a/spec/javascripts/notes/components/noteable_discussion_spec.js
+++ b/spec/javascripts/notes/components/noteable_discussion_spec.js
@@ -14,6 +14,7 @@ describe('noteable_discussion component', () => {
   preloadFixtures(discussionWithTwoUnresolvedNotes);
 
   beforeEach(() => {
+    window.mrTabs = {};
     store = createStore();
     store.dispatch('setNoteableData', noteableDataMock);
     store.dispatch('setNotesData', notesDataMock);
@@ -106,33 +107,29 @@ describe('noteable_discussion component', () => {
 
   describe('methods', () => {
     describe('jumpToNextDiscussion', () => {
-      it('expands next unresolved discussion', () => {
-        spyOn(vm, 'expandDiscussion').and.stub();
-        const discussions = [
-          discussionMock,
-          {
-            ...discussionMock,
-            id: discussionMock.id + 1,
-            notes: [{ ...discussionMock.notes[0], resolvable: true, resolved: true }],
-          },
-          {
-            ...discussionMock,
-            id: discussionMock.id + 2,
-            notes: [{ ...discussionMock.notes[0], resolvable: true, resolved: false }],
-          },
-        ];
-        const nextDiscussionId = discussionMock.id + 2;
-        store.replaceState({
-          ...store.state,
-          discussions,
-        });
-        setFixtures(`
-          <div data-discussion-id="${nextDiscussionId}"></div>
-        `);
+      it('expands next unresolved discussion', done => {
+        const discussion2 = getJSONFixture(discussionWithTwoUnresolvedNotes)[0];
+        discussion2.resolved = false;
+        discussion2.id = 'next'; // prepare this for being identified as next one (to be jumped to)
+        vm.$store.dispatch('setInitialNotes', [discussionMock, discussion2]);
+        window.mrTabs.currentAction = 'show';
+
+        Vue.nextTick()
+          .then(() => {
+            spyOn(vm, 'expandDiscussion').and.stub();
+
+            const nextDiscussionId = discussion2.id;
 
-        vm.jumpToNextDiscussion();
+            setFixtures(`
+              <div class="discussion" data-discussion-id="${nextDiscussionId}"></div>
+            `);
 
-        expect(vm.expandDiscussion).toHaveBeenCalledWith({ discussionId: nextDiscussionId });
+            vm.jumpToNextDiscussion();
+
+            expect(vm.expandDiscussion).toHaveBeenCalledWith({ discussionId: nextDiscussionId });
+          })
+          .then(done)
+          .catch(done.fail);
       });
     });
   });
diff --git a/spec/javascripts/notes/mock_data.js b/spec/javascripts/notes/mock_data.js
index be2a8ba67fe..67f6a9629d9 100644
--- a/spec/javascripts/notes/mock_data.js
+++ b/spec/javascripts/notes/mock_data.js
@@ -1168,3 +1168,87 @@ export const collapsedSystemNotes = [
     diff_discussion: false,
   },
 ];
+
+export const discussion1 = {
+  id: 'abc1',
+  resolvable: true,
+  resolved: false,
+  diff_file: {
+    file_path: 'about.md',
+  },
+  position: {
+    formatter: {
+      new_line: 50,
+      old_line: null,
+    },
+  },
+  notes: [
+    {
+      created_at: '2018-07-04T16:25:41.749Z',
+    },
+  ],
+};
+
+export const resolvedDiscussion1 = {
+  id: 'abc1',
+  resolvable: true,
+  resolved: true,
+  diff_file: {
+    file_path: 'about.md',
+  },
+  position: {
+    formatter: {
+      new_line: 50,
+      old_line: null,
+    },
+  },
+  notes: [
+    {
+      created_at: '2018-07-04T16:25:41.749Z',
+    },
+  ],
+};
+
+export const discussion2 = {
+  id: 'abc2',
+  resolvable: true,
+  resolved: false,
+  diff_file: {
+    file_path: 'README.md',
+  },
+  position: {
+    formatter: {
+      new_line: null,
+      old_line: 20,
+    },
+  },
+  notes: [
+    {
+      created_at: '2018-07-04T12:05:41.749Z',
+    },
+  ],
+};
+
+export const discussion3 = {
+  id: 'abc3',
+  resolvable: true,
+  resolved: false,
+  diff_file: {
+    file_path: 'README.md',
+  },
+  position: {
+    formatter: {
+      new_line: 21,
+      old_line: null,
+    },
+  },
+  notes: [
+    {
+      created_at: '2018-07-05T17:25:41.749Z',
+    },
+  ],
+};
+
+export const unresolvableDiscussion = {
+  resolvable: false,
+};
diff --git a/spec/javascripts/notes/stores/getters_spec.js b/spec/javascripts/notes/stores/getters_spec.js
index 41599e00122..7f8ede51508 100644
--- a/spec/javascripts/notes/stores/getters_spec.js
+++ b/spec/javascripts/notes/stores/getters_spec.js
@@ -5,6 +5,11 @@ import {
   noteableDataMock,
   individualNote,
   collapseNotesMock,
+  discussion1,
+  discussion2,
+  discussion3,
+  resolvedDiscussion1,
+  unresolvableDiscussion,
 } from '../mock_data';
 
 const discussionWithTwoUnresolvedNotes = 'merge_requests/resolved_diff_discussion.json';
@@ -109,4 +114,154 @@ describe('Getters Notes Store', () => {
       expect(getters.isNotesFetched(state)).toBeFalsy();
     });
   });
+
+  describe('allResolvableDiscussions', () => {
+    it('should return only resolvable discussions in same order', () => {
+      const localGetters = {
+        allDiscussions: [
+          discussion3,
+          unresolvableDiscussion,
+          discussion1,
+          unresolvableDiscussion,
+          discussion2,
+        ],
+      };
+
+      expect(getters.allResolvableDiscussions(state, localGetters)).toEqual([
+        discussion3,
+        discussion1,
+        discussion2,
+      ]);
+    });
+
+    it('should return empty array if there are no resolvable discussions', () => {
+      const localGetters = {
+        allDiscussions: [unresolvableDiscussion, unresolvableDiscussion],
+      };
+
+      expect(getters.allResolvableDiscussions(state, localGetters)).toEqual([]);
+    });
+  });
+
+  describe('unresolvedDiscussionsIdsByDiff', () => {
+    it('should return all discussions IDs in diff order', () => {
+      const localGetters = {
+        allResolvableDiscussions: [discussion3, discussion1, discussion2],
+      };
+
+      expect(getters.unresolvedDiscussionsIdsByDiff(state, localGetters)).toEqual([
+        'abc1',
+        'abc2',
+        'abc3',
+      ]);
+    });
+
+    it('should return empty array if all discussions have been resolved', () => {
+      const localGetters = {
+        allResolvableDiscussions: [resolvedDiscussion1],
+      };
+
+      expect(getters.unresolvedDiscussionsIdsByDiff(state, localGetters)).toEqual([]);
+    });
+  });
+
+  describe('unresolvedDiscussionsIdsByDate', () => {
+    it('should return all discussions in date ascending order', () => {
+      const localGetters = {
+        allResolvableDiscussions: [discussion3, discussion1, discussion2],
+      };
+
+      expect(getters.unresolvedDiscussionsIdsByDate(state, localGetters)).toEqual([
+        'abc2',
+        'abc1',
+        'abc3',
+      ]);
+    });
+
+    it('should return empty array if all discussions have been resolved', () => {
+      const localGetters = {
+        allResolvableDiscussions: [resolvedDiscussion1],
+      };
+
+      expect(getters.unresolvedDiscussionsIdsByDate(state, localGetters)).toEqual([]);
+    });
+  });
+
+  describe('unresolvedDiscussionsIdsOrdered', () => {
+    const localGetters = {
+      unresolvedDiscussionsIdsByDate: ['123', '456'],
+      unresolvedDiscussionsIdsByDiff: ['abc', 'def'],
+    };
+
+    it('should return IDs ordered by diff when diffOrder param is true', () => {
+      expect(getters.unresolvedDiscussionsIdsOrdered(state, localGetters)(true)).toEqual([
+        'abc',
+        'def',
+      ]);
+    });
+
+    it('should return IDs ordered by date when diffOrder param is not true', () => {
+      expect(getters.unresolvedDiscussionsIdsOrdered(state, localGetters)(false)).toEqual([
+        '123',
+        '456',
+      ]);
+      expect(getters.unresolvedDiscussionsIdsOrdered(state, localGetters)(undefined)).toEqual([
+        '123',
+        '456',
+      ]);
+    });
+  });
+
+  describe('isLastUnresolvedDiscussion', () => {
+    const localGetters = {
+      unresolvedDiscussionsIdsOrdered: () => ['123', '456', '789'],
+    };
+
+    it('should return true if the discussion id provided is the last', () => {
+      expect(getters.isLastUnresolvedDiscussion(state, localGetters)('789')).toBe(true);
+    });
+
+    it('should return false if the discussion id provided is not the last', () => {
+      expect(getters.isLastUnresolvedDiscussion(state, localGetters)('123')).toBe(false);
+      expect(getters.isLastUnresolvedDiscussion(state, localGetters)('456')).toBe(false);
+    });
+  });
+
+  describe('nextUnresolvedDiscussionId', () => {
+    const localGetters = {
+      unresolvedDiscussionsIdsOrdered: () => ['123', '456', '789'],
+    };
+
+    it('should return the ID of the discussion after the ID provided', () => {
+      expect(getters.nextUnresolvedDiscussionId(state, localGetters)('123')).toBe('456');
+      expect(getters.nextUnresolvedDiscussionId(state, localGetters)('456')).toBe('789');
+      expect(getters.nextUnresolvedDiscussionId(state, localGetters)('789')).toBe(undefined);
+    });
+  });
+
+  describe('firstUnresolvedDiscussionId', () => {
+    const localGetters = {
+      unresolvedDiscussionsIdsByDate: ['123', '456'],
+      unresolvedDiscussionsIdsByDiff: ['abc', 'def'],
+    };
+
+    it('should return the first discussion id by diff when diffOrder param is true', () => {
+      expect(getters.firstUnresolvedDiscussionId(state, localGetters)(true)).toBe('abc');
+    });
+
+    it('should return the first discussion id by date when diffOrder param is not true', () => {
+      expect(getters.firstUnresolvedDiscussionId(state, localGetters)(false)).toBe('123');
+      expect(getters.firstUnresolvedDiscussionId(state, localGetters)(undefined)).toBe('123');
+    });
+
+    it('should be falsy if all discussions are resolved', () => {
+      const localGettersFalsy = {
+        unresolvedDiscussionsIdsByDiff: [],
+        unresolvedDiscussionsIdsByDate: [],
+      };
+
+      expect(getters.firstUnresolvedDiscussionId(state, localGettersFalsy)(true)).toBeFalsy();
+      expect(getters.firstUnresolvedDiscussionId(state, localGettersFalsy)(false)).toBeFalsy();
+    });
+  });
 });