Add latest changes from gitlab-org/gitlab@13-6-stable-eev13.6.0-rc42

21 files changed, 887 insertions, 362 deletions

diff --git a/spec/frontend/diffs/components/app_spec.js b/spec/frontend/diffs/components/app_spec.js
index 86560470ada..225710eab63 100644
--- a/spec/frontend/diffs/components/app_spec.js
+++ b/spec/frontend/diffs/components/app_spec.js
@@ -697,7 +697,7 @@ describe('diffs/components/app', () => {
       });
 
       describe('collapsed files', () => {
-        it('should render the collapsed files warning if there are any collapsed files', () => {
+        it('should render the collapsed files warning if there are any automatically collapsed files', () => {
           createComponent({}, ({ state }) => {
             state.diffs.diffFiles = [{ viewer: { automaticallyCollapsed: true } }];
           });
@@ -705,16 +705,14 @@ describe('diffs/components/app', () => {
           expect(getCollapsedFilesWarning(wrapper).exists()).toBe(true);
         });
 
-        it('should not render the collapsed files warning if the user has dismissed the alert already', async () => {
+        it('should not render the collapsed files warning if there are no automatically collapsed files', () => {
           createComponent({}, ({ state }) => {
-            state.diffs.diffFiles = [{ viewer: { automaticallyCollapsed: true } }];
+            state.diffs.diffFiles = [
+              { viewer: { automaticallyCollapsed: false, manuallyCollapsed: true } },
+              { viewer: { automaticallyCollapsed: false, manuallyCollapsed: false } },
+            ];
           });
 
-          expect(getCollapsedFilesWarning(wrapper).exists()).toBe(true);
-
-          wrapper.vm.collapsedWarningDismissed = true;
-          await wrapper.vm.$nextTick();
-
           expect(getCollapsedFilesWarning(wrapper).exists()).toBe(false);
         });
       });
diff --git a/spec/frontend/diffs/components/collapsed_files_warning_spec.js b/spec/frontend/diffs/components/collapsed_files_warning_spec.js
index 7bbffb7a1cd..75e76d88b6b 100644
--- a/spec/frontend/diffs/components/collapsed_files_warning_spec.js
+++ b/spec/frontend/diffs/components/collapsed_files_warning_spec.js
@@ -2,7 +2,8 @@ import Vuex from 'vuex';
 import { shallowMount, mount, createLocalVue } from '@vue/test-utils';
 import createStore from '~/diffs/store/modules';
 import CollapsedFilesWarning from '~/diffs/components/collapsed_files_warning.vue';
-import { CENTERED_LIMITED_CONTAINER_CLASSES } from '~/diffs/constants';
+import { CENTERED_LIMITED_CONTAINER_CLASSES, EVT_EXPAND_ALL_FILES } from '~/diffs/constants';
+import eventHub from '~/diffs/event_hub';
 
 const propsData = {
   limited: true,
@@ -76,13 +77,13 @@ describe('CollapsedFilesWarning', () => {
     expect(wrapper.find('[data-testid="root"]').exists()).toBe(false);
   });
 
-  it('triggers the expandAllFiles action when the alert action button is clicked', () => {
+  it(`emits the \`${EVT_EXPAND_ALL_FILES}\` event when the alert action button is clicked`, () => {
     createComponent({}, { full: true });
 
-    jest.spyOn(wrapper.vm.$store, 'dispatch').mockReturnValue(undefined);
+    jest.spyOn(eventHub, '$emit');
 
     getAlertActionButton().vm.$emit('click');
 
-    expect(wrapper.vm.$store.dispatch).toHaveBeenCalledWith('diffs/expandAllFiles', undefined);
+    expect(eventHub.$emit).toHaveBeenCalledWith(EVT_EXPAND_ALL_FILES);
   });
 });
diff --git a/spec/frontend/diffs/components/diff_comment_cell_spec.js b/spec/frontend/diffs/components/diff_comment_cell_spec.js
new file mode 100644
index 00000000000..d6b68fc52d7
--- /dev/null
+++ b/spec/frontend/diffs/components/diff_comment_cell_spec.js
@@ -0,0 +1,43 @@
+import { shallowMount } from '@vue/test-utils';
+import DiffCommentCell from '~/diffs/components/diff_comment_cell.vue';
+import DiffDiscussions from '~/diffs/components/diff_discussions.vue';
+import DiffDiscussionReply from '~/diffs/components/diff_discussion_reply.vue';
+
+describe('DiffCommentCell', () => {
+  const createWrapper = (props = {}) => {
+    const { renderDiscussion, ...otherProps } = props;
+    const line = {
+      discussions: [],
+      renderDiscussion,
+    };
+    const diffFileHash = 'abc';
+
+    return shallowMount(DiffCommentCell, {
+      propsData: { line, diffFileHash, ...otherProps },
+    });
+  };
+
+  it('renders discussions if line has discussions', () => {
+    const wrapper = createWrapper({ renderDiscussion: true });
+
+    expect(wrapper.find(DiffDiscussions).exists()).toBe(true);
+  });
+
+  it('does not render discussions if line has no discussions', () => {
+    const wrapper = createWrapper();
+
+    expect(wrapper.find(DiffDiscussions).exists()).toBe(false);
+  });
+
+  it('renders discussion reply if line has no draft', () => {
+    const wrapper = createWrapper();
+
+    expect(wrapper.find(DiffDiscussionReply).exists()).toBe(true);
+  });
+
+  it('does not render discussion reply if line has draft', () => {
+    const wrapper = createWrapper({ hasDraft: true });
+
+    expect(wrapper.find(DiffDiscussionReply).exists()).toBe(false);
+  });
+});
diff --git a/spec/frontend/diffs/components/diff_content_spec.js b/spec/frontend/diffs/components/diff_content_spec.js
index 6d0120d888e..e3a6f7f16a9 100644
--- a/spec/frontend/diffs/components/diff_content_spec.js
+++ b/spec/frontend/diffs/components/diff_content_spec.js
@@ -12,6 +12,8 @@ import DiffDiscussions from '~/diffs/components/diff_discussions.vue';
 import { IMAGE_DIFF_POSITION_TYPE } from '~/diffs/constants';
 import diffFileMockData from '../mock_data/diff_file';
 import { diffViewerModes } from '~/ide/constants';
+import { diffLines } from '~/diffs/store/getters';
+import DiffView from '~/diffs/components/diff_view.vue';
 
 const localVue = createLocalVue();
 localVue.use(Vuex);
@@ -33,7 +35,7 @@ describe('DiffContent', () => {
     diffFile: JSON.parse(JSON.stringify(diffFileMockData)),
   };
 
-  const createComponent = ({ props, state } = {}) => {
+  const createComponent = ({ props, state, provide } = {}) => {
     const fakeStore = new Vuex.Store({
       getters: {
         getNoteableData() {
@@ -55,6 +57,10 @@ describe('DiffContent', () => {
           namespaced: true,
           getters: {
             draftsForFile: () => () => true,
+            draftForLine: () => () => true,
+            shouldRenderDraftRow: () => () => true,
+            hasParallelDraftLeft: () => () => true,
+            hasParallelDraftRight: () => () => true,
           },
         },
         diffs: {
@@ -68,6 +74,7 @@ describe('DiffContent', () => {
             isInlineView: isInlineViewGetterMock,
             isParallelView: isParallelViewGetterMock,
             getCommentFormForDiffFile: getCommentFormForDiffFileGetterMock,
+            diffLines,
           },
           actions: {
             saveDiffDiscussion: saveDiffDiscussionMock,
@@ -77,6 +84,8 @@ describe('DiffContent', () => {
       },
     });
 
+    const glFeatures = provide ? { ...provide.glFeatures } : {};
+
     wrapper = shallowMount(DiffContentComponent, {
       propsData: {
         ...defaultProps,
@@ -84,6 +93,7 @@ describe('DiffContent', () => {
       },
       localVue,
       store: fakeStore,
+      provide: { glFeatures },
     });
   };
 
@@ -112,6 +122,16 @@ describe('DiffContent', () => {
       expect(wrapper.find(ParallelDiffView).exists()).toBe(true);
     });
 
+    it('should render diff view if `unifiedDiffLines` & `unifiedDiffComponents` are true', () => {
+      isParallelViewGetterMock.mockReturnValue(true);
+      createComponent({
+        props: { diffFile: textDiffFile },
+        provide: { glFeatures: { unifiedDiffLines: true, unifiedDiffComponents: true } },
+      });
+
+      expect(wrapper.find(DiffView).exists()).toBe(true);
+    });
+
     it('renders rendering more lines loading icon', () => {
       createComponent({ props: { diffFile: { ...textDiffFile, renderingLines: true } } });
 
diff --git a/spec/frontend/diffs/components/diff_file_header_spec.js b/spec/frontend/diffs/components/diff_file_header_spec.js
index a04486fc5c7..1b41456f2f5 100644
--- a/spec/frontend/diffs/components/diff_file_header_spec.js
+++ b/spec/frontend/diffs/components/diff_file_header_spec.js
@@ -1,8 +1,12 @@
 import { shallowMount, createLocalVue } from '@vue/test-utils';
 import Vuex from 'vuex';
 import { cloneDeep } from 'lodash';
+
+import { mockTracking, triggerEvent } from 'helpers/tracking_helper';
+
 import DiffFileHeader from '~/diffs/components/diff_file_header.vue';
 import ClipboardButton from '~/vue_shared/components/clipboard_button.vue';
+import FileIcon from '~/vue_shared/components/file_icon.vue';
 import diffDiscussionsMockData from '../mock_data/diff_discussions';
 import { truncateSha } from '~/lib/utils/text_utility';
 import { diffViewerModes } from '~/ide/constants';
@@ -136,9 +140,25 @@ describe('DiffFileHeader component', () => {
     });
   });
 
-  it('displays a copy to clipboard button', () => {
-    createComponent();
-    expect(wrapper.find(ClipboardButton).exists()).toBe(true);
+  describe('copy to clipboard', () => {
+    beforeEach(() => {
+      createComponent();
+    });
+
+    it('displays a copy to clipboard button', () => {
+      expect(wrapper.find(ClipboardButton).exists()).toBe(true);
+    });
+
+    it('triggers the copy to clipboard tracking event', () => {
+      const trackingSpy = mockTracking('_category_', wrapper.vm.$el, jest.spyOn);
+
+      triggerEvent('[data-testid="diff-file-copy-clipboard"]');
+
+      expect(trackingSpy).toHaveBeenCalledWith('_category_', 'click_copy_file_button', {
+        label: 'diff_copy_file_path_button',
+        property: 'diff_copy_file',
+      });
+    });
   });
 
   describe('for submodule', () => {
@@ -188,6 +208,14 @@ describe('DiffFileHeader component', () => {
       });
       expect(findFileActions().exists()).toBe(false);
     });
+
+    it('renders submodule icon', () => {
+      createComponent({
+        diffFile: submoduleDiffFile,
+      });
+
+      expect(wrapper.find(FileIcon).props('submodule')).toBe(true);
+    });
   });
 
   describe('for any file', () => {
diff --git a/spec/frontend/diffs/components/diff_file_spec.js b/spec/frontend/diffs/components/diff_file_spec.js
index a6f0d2bf11d..71e0ffd176f 100644
--- a/spec/frontend/diffs/components/diff_file_spec.js
+++ b/spec/frontend/diffs/components/diff_file_spec.js
@@ -1,262 +1,422 @@
-import Vue from 'vue';
-import { createComponentWithStore } from 'helpers/vue_mount_component_helper';
-import { mockTracking, triggerEvent } from 'helpers/tracking_helper';
-import { createStore } from '~/mr_notes/stores';
-import DiffFileComponent from '~/diffs/components/diff_file.vue';
-import { diffViewerModes, diffViewerErrors } from '~/ide/constants';
+import Vuex from 'vuex';
+import { shallowMount, createLocalVue } from '@vue/test-utils';
+
+import createDiffsStore from '~/diffs/store/modules';
+import createNotesStore from '~/notes/stores/modules';
 import diffFileMockDataReadable from '../mock_data/diff_file';
 import diffFileMockDataUnreadable from '../mock_data/diff_file_unreadable';
 
-describe('DiffFile', () => {
-  let vm;
-  let trackingSpy;
+import DiffFileComponent from '~/diffs/components/diff_file.vue';
+import DiffFileHeaderComponent from '~/diffs/components/diff_file_header.vue';
+import DiffContentComponent from '~/diffs/components/diff_content.vue';
 
-  beforeEach(() => {
-    vm = createComponentWithStore(Vue.extend(DiffFileComponent), createStore(), {
-      file: JSON.parse(JSON.stringify(diffFileMockDataReadable)),
+import eventHub from '~/diffs/event_hub';
+import {
+  EVT_EXPAND_ALL_FILES,
+  EVT_PERF_MARK_DIFF_FILES_END,
+  EVT_PERF_MARK_FIRST_DIFF_FILE_SHOWN,
+} from '~/diffs/constants';
+
+import { diffViewerModes, diffViewerErrors } from '~/ide/constants';
+
+function changeViewer(store, index, { automaticallyCollapsed, manuallyCollapsed, name }) {
+  const file = store.state.diffs.diffFiles[index];
+  const newViewer = {
+    ...file.viewer,
+  };
+
+  if (automaticallyCollapsed !== undefined) {
+    newViewer.automaticallyCollapsed = automaticallyCollapsed;
+  }
+
+  if (manuallyCollapsed !== undefined) {
+    newViewer.manuallyCollapsed = manuallyCollapsed;
+  }
+
+  if (name !== undefined) {
+    newViewer.name = name;
+  }
+
+  Object.assign(file, {
+    viewer: newViewer,
+  });
+}
+
+function forceHasDiff({ store, index = 0, inlineLines, parallelLines, readableText }) {
+  const file = store.state.diffs.diffFiles[index];
+
+  Object.assign(file, {
+    highlighted_diff_lines: inlineLines,
+    parallel_diff_lines: parallelLines,
+    blob: {
+      ...file.blob,
+      readable_text: readableText,
+    },
+  });
+}
+
+function markFileToBeRendered(store, index = 0) {
+  const file = store.state.diffs.diffFiles[index];
+
+  Object.assign(file, {
+    renderIt: true,
+  });
+}
+
+function createComponent({ file, first = false, last = false }) {
+  const localVue = createLocalVue();
+
+  localVue.use(Vuex);
+
+  const store = new Vuex.Store({
+    ...createNotesStore(),
+    modules: {
+      diffs: createDiffsStore(),
+    },
+  });
+
+  store.state.diffs.diffFiles = [file];
+
+  const wrapper = shallowMount(DiffFileComponent, {
+    store,
+    localVue,
+    propsData: {
+      file,
       canCurrentUserFork: false,
       viewDiffsFileByFile: false,
-    }).$mount();
-    trackingSpy = mockTracking('_category_', vm.$el, jest.spyOn);
+      isFirstFile: first,
+      isLastFile: last,
+    },
+  });
+
+  return {
+    localVue,
+    wrapper,
+    store,
+  };
+}
+
+const findDiffHeader = wrapper => wrapper.find(DiffFileHeaderComponent);
+const findDiffContentArea = wrapper => wrapper.find('[data-testid="content-area"]');
+const findLoader = wrapper => wrapper.find('[data-testid="loader-icon"]');
+const findToggleButton = wrapper => wrapper.find('[data-testid="expand-button"]');
+
+const toggleFile = wrapper => findDiffHeader(wrapper).vm.$emit('toggleFile');
+const isDisplayNone = element => element.style.display === 'none';
+const getReadableFile = () => JSON.parse(JSON.stringify(diffFileMockDataReadable));
+const getUnreadableFile = () => JSON.parse(JSON.stringify(diffFileMockDataUnreadable));
+
+const makeFileAutomaticallyCollapsed = (store, index = 0) =>
+  changeViewer(store, index, { automaticallyCollapsed: true, manuallyCollapsed: null });
+const makeFileOpenByDefault = (store, index = 0) =>
+  changeViewer(store, index, { automaticallyCollapsed: false, manuallyCollapsed: null });
+const makeFileManuallyCollapsed = (store, index = 0) =>
+  changeViewer(store, index, { automaticallyCollapsed: false, manuallyCollapsed: true });
+const changeViewerType = (store, newType, index = 0) =>
+  changeViewer(store, index, { name: diffViewerModes[newType] });
+
+describe('DiffFile', () => {
+  let wrapper;
+  let store;
+
+  beforeEach(() => {
+    ({ wrapper, store } = createComponent({ file: getReadableFile() }));
   });
 
   afterEach(() => {
-    vm.$destroy();
+    wrapper.destroy();
+    wrapper = null;
   });
 
-  const findDiffContent = () => vm.$el.querySelector('.diff-content');
-  const isVisible = el => el.style.display !== 'none';
+  describe('bus events', () => {
+    beforeEach(() => {
+      jest.spyOn(eventHub, '$emit').mockImplementation(() => {});
+    });
+
+    describe('during mount', () => {
+      it.each`
+        first    | last     | events                                                                 | file
+        ${false} | ${false} | ${[]}                                                                  | ${{ inlineLines: [], parallelLines: [], readableText: true }}
+        ${true}  | ${true}  | ${[]}                                                                  | ${{ inlineLines: [], parallelLines: [], readableText: true }}
+        ${true}  | ${false} | ${[EVT_PERF_MARK_FIRST_DIFF_FILE_SHOWN]}                               | ${false}
+        ${false} | ${true}  | ${[EVT_PERF_MARK_DIFF_FILES_END]}                                      | ${false}
+        ${true}  | ${true}  | ${[EVT_PERF_MARK_FIRST_DIFF_FILE_SHOWN, EVT_PERF_MARK_DIFF_FILES_END]} | ${false}
+      `(
+        'emits the events $events based on the file and its position ({ first: $first, last: $last }) among all files',
+        async ({ file, first, last, events }) => {
+          if (file) {
+            forceHasDiff({ store, ...file });
+          }
+
+          ({ wrapper, store } = createComponent({
+            file: store.state.diffs.diffFiles[0],
+            first,
+            last,
+          }));
+
+          await wrapper.vm.$nextTick();
+
+          expect(eventHub.$emit).toHaveBeenCalledTimes(events.length);
+          events.forEach(event => {
+            expect(eventHub.$emit).toHaveBeenCalledWith(event);
+          });
+        },
+      );
+    });
+
+    describe('after loading the diff', () => {
+      it('indicates that it loaded the file', async () => {
+        forceHasDiff({ store, inlineLines: [], parallelLines: [], readableText: true });
+        ({ wrapper, store } = createComponent({
+          file: store.state.diffs.diffFiles[0],
+          first: true,
+          last: true,
+        }));
+
+        jest.spyOn(wrapper.vm, 'loadCollapsedDiff').mockResolvedValue(getReadableFile());
+        jest.spyOn(window, 'requestIdleCallback').mockImplementation(fn => fn());
+
+        makeFileAutomaticallyCollapsed(store);
+
+        await wrapper.vm.$nextTick(); // Wait for store updates to flow into the component
+
+        toggleFile(wrapper);
+
+        await wrapper.vm.$nextTick(); // Wait for the load to resolve
+        await wrapper.vm.$nextTick(); // Wait for the idleCallback
+        await wrapper.vm.$nextTick(); // Wait for nextTick inside postRender
+
+        expect(eventHub.$emit).toHaveBeenCalledTimes(2);
+        expect(eventHub.$emit).toHaveBeenCalledWith(EVT_PERF_MARK_FIRST_DIFF_FILE_SHOWN);
+        expect(eventHub.$emit).toHaveBeenCalledWith(EVT_PERF_MARK_DIFF_FILES_END);
+      });
+    });
+  });
 
   describe('template', () => {
-    it('should render component with file header, file content components', done => {
-      const el = vm.$el;
-      const { file_hash, file_path } = vm.file;
+    it('should render component with file header, file content components', async () => {
+      const el = wrapper.vm.$el;
+      const { file_hash } = wrapper.vm.file;
 
       expect(el.id).toEqual(file_hash);
       expect(el.classList.contains('diff-file')).toEqual(true);
 
       expect(el.querySelectorAll('.diff-content.hidden').length).toEqual(0);
       expect(el.querySelector('.js-file-title')).toBeDefined();
-      expect(el.querySelector('[data-testid="diff-file-copy-clipboard"]')).toBeDefined();
-      expect(el.querySelector('.file-title-name').innerText.indexOf(file_path)).toBeGreaterThan(-1);
+      expect(wrapper.find(DiffFileHeaderComponent).exists()).toBe(true);
       expect(el.querySelector('.js-syntax-highlight')).toBeDefined();
 
-      vm.file.renderIt = true;
+      markFileToBeRendered(store);
+
+      await wrapper.vm.$nextTick();
 
-      vm.$nextTick()
-        .then(() => {
-          expect(el.querySelectorAll('.line_content').length).toBe(8);
-          expect(el.querySelectorAll('.js-line-expansion-content').length).toBe(1);
-          triggerEvent('[data-testid="diff-file-copy-clipboard"]');
-        })
-        .then(done)
-        .catch(done.fail);
+      expect(wrapper.find(DiffContentComponent).exists()).toBe(true);
     });
+  });
 
-    it('should track a click event on copy to clip board button', done => {
-      const el = vm.$el;
+  describe('collapsing', () => {
+    describe(`\`${EVT_EXPAND_ALL_FILES}\` event`, () => {
+      beforeEach(() => {
+        jest.spyOn(wrapper.vm, 'handleToggle').mockImplementation(() => {});
+      });
 
-      expect(el.querySelector('[data-testid="diff-file-copy-clipboard"]')).toBeDefined();
-      vm.file.renderIt = true;
-      vm.$nextTick()
-        .then(() => {
-          triggerEvent('[data-testid="diff-file-copy-clipboard"]');
+      it('performs the normal file toggle when the file is collapsed', async () => {
+        makeFileAutomaticallyCollapsed(store);
 
-          expect(trackingSpy).toHaveBeenCalledWith('_category_', 'click_copy_file_button', {
-            label: 'diff_copy_file_path_button',
-            property: 'diff_copy_file',
-          });
-        })
-        .then(done)
-        .catch(done.fail);
-    });
+        await wrapper.vm.$nextTick();
 
-    describe('collapsed', () => {
-      it('should not have file content', done => {
-        expect(isVisible(findDiffContent())).toBe(true);
-        expect(vm.isCollapsed).toEqual(false);
-        vm.isCollapsed = true;
-        vm.file.renderIt = true;
+        eventHub.$emit(EVT_EXPAND_ALL_FILES);
 
-        vm.$nextTick(() => {
-          expect(isVisible(findDiffContent())).toBe(false);
-
-          done();
-        });
+        expect(wrapper.vm.handleToggle).toHaveBeenCalledTimes(1);
       });
 
-      it('should have collapsed text and link', done => {
-        vm.renderIt = true;
-        vm.isCollapsed = true;
+      it('does nothing when the file is not collapsed', async () => {
+        eventHub.$emit(EVT_EXPAND_ALL_FILES);
 
-        vm.$nextTick(() => {
-          expect(vm.$el.innerText).toContain('This diff is collapsed');
-          expect(vm.$el.querySelectorAll('.js-click-to-expand').length).toEqual(1);
+        await wrapper.vm.$nextTick();
 
-          done();
-        });
+        expect(wrapper.vm.handleToggle).not.toHaveBeenCalled();
       });
+    });
 
-      it('should have collapsed text and link even before rendered', done => {
-        vm.renderIt = false;
-        vm.isCollapsed = true;
+    describe('user collapsed', () => {
+      beforeEach(() => {
+        makeFileManuallyCollapsed(store);
+      });
 
-        vm.$nextTick(() => {
-          expect(vm.$el.innerText).toContain('This diff is collapsed');
-          expect(vm.$el.querySelectorAll('.js-click-to-expand').length).toEqual(1);
+      it('should not have any content at all', async () => {
+        await wrapper.vm.$nextTick();
 
-          done();
+        Array.from(findDiffContentArea(wrapper).element.children).forEach(child => {
+          expect(isDisplayNone(child)).toBe(true);
         });
       });
 
-      it('should be collapsable for unreadable files', done => {
-        vm.$destroy();
-        vm = createComponentWithStore(Vue.extend(DiffFileComponent), createStore(), {
-          file: JSON.parse(JSON.stringify(diffFileMockDataUnreadable)),
-          canCurrentUserFork: false,
-          viewDiffsFileByFile: false,
-        }).$mount();
+      it('should not have the class `has-body` to present the header differently', () => {
+        expect(wrapper.classes('has-body')).toBe(false);
+      });
+    });
 
-        vm.renderIt = false;
-        vm.isCollapsed = true;
+    describe('automatically collapsed', () => {
+      beforeEach(() => {
+        makeFileAutomaticallyCollapsed(store);
+      });
 
-        vm.$nextTick(() => {
-          expect(vm.$el.innerText).toContain('This diff is collapsed');
-          expect(vm.$el.querySelectorAll('.js-click-to-expand').length).toEqual(1);
+      it('should show the collapsed file warning with expansion button', () => {
+        expect(findDiffContentArea(wrapper).html()).toContain(
+          'Files with large changes are collapsed by default.',
+        );
+        expect(findToggleButton(wrapper).exists()).toBe(true);
+      });
 
-          done();
-        });
+      it('should style the component so that it `.has-body` for layout purposes', () => {
+        expect(wrapper.classes('has-body')).toBe(true);
       });
+    });
 
-      it('should be collapsed for renamed files', done => {
-        vm.renderIt = true;
-        vm.isCollapsed = false;
-        vm.file.highlighted_diff_lines = null;
-        vm.file.viewer.name = diffViewerModes.renamed;
+    describe('not collapsed', () => {
+      beforeEach(() => {
+        makeFileOpenByDefault(store);
+        markFileToBeRendered(store);
+      });
 
-        vm.$nextTick(() => {
-          expect(vm.$el.innerText).not.toContain('This diff is collapsed');
+      it('should have the file content', async () => {
+        expect(wrapper.find(DiffContentComponent).exists()).toBe(true);
+      });
 
-          done();
-        });
+      it('should style the component so that it `.has-body` for layout purposes', () => {
+        expect(wrapper.classes('has-body')).toBe(true);
       });
+    });
 
-      it('should be collapsed for mode changed files', done => {
-        vm.renderIt = true;
-        vm.isCollapsed = false;
-        vm.file.highlighted_diff_lines = null;
-        vm.file.viewer.name = diffViewerModes.mode_changed;
+    describe('toggle', () => {
+      it('should update store state', async () => {
+        jest.spyOn(wrapper.vm.$store, 'dispatch').mockImplementation(() => {});
 
-        vm.$nextTick(() => {
-          expect(vm.$el.innerText).not.toContain('This diff is collapsed');
+        toggleFile(wrapper);
 
-          done();
+        expect(wrapper.vm.$store.dispatch).toHaveBeenCalledWith('diffs/setFileCollapsedByUser', {
+          filePath: wrapper.vm.file.file_path,
+          collapsed: true,
         });
       });
 
-      it('should have loading icon while loading a collapsed diffs', done => {
-        vm.isCollapsed = true;
-        vm.isLoadingCollapsedDiff = true;
+      describe('fetch collapsed diff', () => {
+        const prepFile = async (inlineLines, parallelLines, readableText) => {
+          forceHasDiff({
+            store,
+            inlineLines,
+            parallelLines,
+            readableText,
+          });
+
+          await wrapper.vm.$nextTick();
 
-        vm.$nextTick(() => {
-          expect(vm.$el.querySelectorAll('.diff-content.loading').length).toEqual(1);
+          toggleFile(wrapper);
+        };
 
-          done();
+        beforeEach(() => {
+          jest.spyOn(wrapper.vm, 'requestDiff').mockImplementation(() => {});
+
+          makeFileAutomaticallyCollapsed(store);
         });
-      });
 
-      it('should update store state', done => {
-        jest.spyOn(vm.$store, 'dispatch').mockImplementation(() => {});
+        it.each`
+          inlineLines | parallelLines | readableText
+          ${[1]}      | ${[1]}        | ${true}
+          ${[]}       | ${[1]}        | ${true}
+          ${[1]}      | ${[]}         | ${true}
+          ${[1]}      | ${[1]}        | ${false}
+          ${[]}       | ${[]}         | ${false}
+        `(
+          'does not make a request to fetch the diff for a diff file like { inline: $inlineLines, parallel: $parallelLines, readableText: $readableText }',
+          async ({ inlineLines, parallelLines, readableText }) => {
+            await prepFile(inlineLines, parallelLines, readableText);
+
+            expect(wrapper.vm.requestDiff).not.toHaveBeenCalled();
+          },
+        );
 
-        vm.isCollapsed = true;
+        it.each`
+          inlineLines | parallelLines | readableText
+          ${[]}       | ${[]}         | ${true}
+        `(
+          'makes a request to fetch the diff for a diff file like { inline: $inlineLines, parallel: $parallelLines, readableText: $readableText }',
+          async ({ inlineLines, parallelLines, readableText }) => {
+            await prepFile(inlineLines, parallelLines, readableText);
 
-        vm.$nextTick(() => {
-          expect(vm.$store.dispatch).toHaveBeenCalledWith('diffs/setFileCollapsed', {
-            filePath: vm.file.file_path,
-            collapsed: true,
-          });
+            expect(wrapper.vm.requestDiff).toHaveBeenCalled();
+          },
+        );
+      });
+    });
 
-          done();
-        });
+    describe('loading', () => {
+      it('should have loading icon while loading a collapsed diffs', async () => {
+        makeFileAutomaticallyCollapsed(store);
+        wrapper.vm.isLoadingCollapsedDiff = true;
+
+        await wrapper.vm.$nextTick();
+
+        expect(findLoader(wrapper).exists()).toBe(true);
       });
+    });
 
-      it('updates local state when changing file state', done => {
-        vm.file.viewer.automaticallyCollapsed = true;
+    describe('general (other) collapsed', () => {
+      it('should be expandable for unreadable files', async () => {
+        ({ wrapper, store } = createComponent({ file: getUnreadableFile() }));
+        makeFileAutomaticallyCollapsed(store);
 
-        vm.$nextTick(() => {
-          expect(vm.isCollapsed).toBe(true);
+        await wrapper.vm.$nextTick();
 
-          done();
-        });
+        expect(findDiffContentArea(wrapper).html()).toContain(
+          'Files with large changes are collapsed by default.',
+        );
+        expect(findToggleButton(wrapper).exists()).toBe(true);
       });
+
+      it.each`
+        mode
+        ${'renamed'}
+        ${'mode_changed'}
+      `(
+        'should render the DiffContent component for files whose mode is $mode',
+        async ({ mode }) => {
+          makeFileOpenByDefault(store);
+          markFileToBeRendered(store);
+          changeViewerType(store, mode);
+
+          await wrapper.vm.$nextTick();
+
+          expect(wrapper.classes('has-body')).toBe(true);
+          expect(wrapper.find(DiffContentComponent).exists()).toBe(true);
+          expect(wrapper.find(DiffContentComponent).isVisible()).toBe(true);
+        },
+      );
     });
   });
 
   describe('too large diff', () => {
-    it('should have too large warning and blob link', done => {
+    it('should have too large warning and blob link', async () => {
+      const file = store.state.diffs.diffFiles[0];
       const BLOB_LINK = '/file/view/path';
-      vm.file.viewer.error = diffViewerErrors.too_large;
-      vm.file.viewer.error_message =
-        'This source diff could not be displayed because it is too large';
-      vm.file.view_path = BLOB_LINK;
-      vm.file.renderIt = true;
-
-      vm.$nextTick(() => {
-        expect(vm.$el.innerText).toContain(
-          'This source diff could not be displayed because it is too large',
-        );
 
-        done();
+      Object.assign(store.state.diffs.diffFiles[0], {
+        ...file,
+        view_path: BLOB_LINK,
+        renderIt: true,
+        viewer: {
+          ...file.viewer,
+          error: diffViewerErrors.too_large,
+          error_message: 'This source diff could not be displayed because it is too large',
+        },
       });
-    });
-  });
 
-  describe('watch collapsed', () => {
-    it('calls handleLoadCollapsedDiff if collapsed changed & file has no lines', done => {
-      jest.spyOn(vm, 'handleLoadCollapsedDiff').mockImplementation(() => {});
-
-      vm.file.highlighted_diff_lines = [];
-      vm.file.parallel_diff_lines = [];
-      vm.isCollapsed = true;
-
-      vm.$nextTick()
-        .then(() => {
-          vm.isCollapsed = false;
-
-          return vm.$nextTick();
-        })
-        .then(() => {
-          expect(vm.handleLoadCollapsedDiff).toHaveBeenCalled();
-        })
-        .then(done)
-        .catch(done.fail);
-    });
+      await wrapper.vm.$nextTick();
 
-    it('does not call handleLoadCollapsedDiff if collapsed changed & file is unreadable', done => {
-      vm.$destroy();
-      vm = createComponentWithStore(Vue.extend(DiffFileComponent), createStore(), {
-        file: JSON.parse(JSON.stringify(diffFileMockDataUnreadable)),
-        canCurrentUserFork: false,
-        viewDiffsFileByFile: false,
-      }).$mount();
-
-      jest.spyOn(vm, 'handleLoadCollapsedDiff').mockImplementation(() => {});
-
-      vm.file.highlighted_diff_lines = [];
-      vm.file.parallel_diff_lines = undefined;
-      vm.isCollapsed = true;
-
-      vm.$nextTick()
-        .then(() => {
-          vm.isCollapsed = false;
-
-          return vm.$nextTick();
-        })
-        .then(() => {
-          expect(vm.handleLoadCollapsedDiff).not.toHaveBeenCalled();
-        })
-        .then(done)
-        .catch(done.fail);
+      expect(wrapper.vm.$el.innerText).toContain(
+        'This source diff could not be displayed because it is too large',
+      );
     });
   });
 });
diff --git a/spec/frontend/diffs/components/diff_row_spec.js b/spec/frontend/diffs/components/diff_row_spec.js
new file mode 100644
index 00000000000..f9e76cf8107
--- /dev/null
+++ b/spec/frontend/diffs/components/diff_row_spec.js
@@ -0,0 +1,127 @@
+import { shallowMount, createLocalVue } from '@vue/test-utils';
+import Vuex from 'vuex';
+import diffsModule from '~/diffs/store/modules';
+import DiffRow from '~/diffs/components/diff_row.vue';
+
+describe('DiffRow', () => {
+  const testLines = [
+    {
+      left: { old_line: 1, discussions: [] },
+      right: { new_line: 1, discussions: [] },
+      hasDiscussionsLeft: true,
+      hasDiscussionsRight: true,
+    },
+    {
+      left: {},
+      right: {},
+      isMatchLineLeft: true,
+      isMatchLineRight: true,
+    },
+    {},
+    {
+      left: { old_line: 1, discussions: [] },
+      right: { new_line: 1, discussions: [] },
+    },
+  ];
+
+  const createWrapper = ({ props, state, isLoggedIn = true }) => {
+    const localVue = createLocalVue();
+    localVue.use(Vuex);
+
+    const diffs = diffsModule();
+    diffs.state = { ...diffs.state, ...state };
+
+    const getters = { isLoggedIn: () => isLoggedIn };
+
+    const store = new Vuex.Store({
+      modules: { diffs },
+      getters,
+    });
+
+    const propsData = {
+      fileHash: 'abc',
+      filePath: 'abc',
+      line: {},
+      ...props,
+    };
+    return shallowMount(DiffRow, { propsData, localVue, store });
+  };
+
+  it('isHighlighted returns true if isCommented is true', () => {
+    const props = { isCommented: true };
+    const wrapper = createWrapper({ props });
+    expect(wrapper.vm.isHighlighted).toBe(true);
+  });
+
+  it('isHighlighted returns true given line.left', () => {
+    const props = {
+      line: {
+        left: {
+          line_code: 'abc',
+        },
+      },
+    };
+    const state = { highlightedRow: 'abc' };
+    const wrapper = createWrapper({ props, state });
+    expect(wrapper.vm.isHighlighted).toBe(true);
+  });
+
+  it('isHighlighted returns true given line.right', () => {
+    const props = {
+      line: {
+        right: {
+          line_code: 'abc',
+        },
+      },
+    };
+    const state = { highlightedRow: 'abc' };
+    const wrapper = createWrapper({ props, state });
+    expect(wrapper.vm.isHighlighted).toBe(true);
+  });
+
+  it('isHighlighted returns false given line.left', () => {
+    const props = {
+      line: {
+        left: {
+          line_code: 'abc',
+        },
+      },
+    };
+    const wrapper = createWrapper({ props });
+    expect(wrapper.vm.isHighlighted).toBe(false);
+  });
+
+  describe.each`
+    side
+    ${'left'}
+    ${'right'}
+  `('$side side', ({ side }) => {
+    it(`renders empty cells if ${side} is unavailable`, () => {
+      const wrapper = createWrapper({ props: { line: testLines[2] } });
+      expect(wrapper.find(`[data-testid="${side}LineNumber"]`).exists()).toBe(false);
+      expect(wrapper.find(`[data-testid="${side}EmptyCell"]`).exists()).toBe(true);
+    });
+
+    it('renders comment button', () => {
+      const wrapper = createWrapper({ props: { line: testLines[3] } });
+      expect(wrapper.find(`[data-testid="${side}CommentButton"]`).exists()).toBe(true);
+    });
+
+    it('renders avatars', () => {
+      const wrapper = createWrapper({ props: { line: testLines[0] } });
+      expect(wrapper.find(`[data-testid="${side}Discussions"]`).exists()).toBe(true);
+    });
+  });
+
+  it('renders left line numbers', () => {
+    const wrapper = createWrapper({ props: { line: testLines[0] } });
+    const lineNumber = testLines[0].left.old_line;
+    expect(wrapper.find(`[data-linenumber="${lineNumber}"]`).exists()).toBe(true);
+  });
+
+  it('renders right line numbers', () => {
+    const wrapper = createWrapper({ props: { line: testLines[0] } });
+    const lineNumber = testLines[0].right.new_line;
+    expect(wrapper.find(`[data-linenumber="${lineNumber}"]`).exists()).toBe(true);
+  });
+});
diff --git a/spec/frontend/diffs/components/diff_row_utils_spec.js b/spec/frontend/diffs/components/diff_row_utils_spec.js
index 394b6cb1914..c001857fa49 100644
--- a/spec/frontend/diffs/components/diff_row_utils_spec.js
+++ b/spec/frontend/diffs/components/diff_row_utils_spec.js
@@ -201,3 +201,76 @@ describe('shouldShowCommentButton', () => {
     },
   );
 });
+
+describe('mapParallel', () => {
+  it('should assign computed properties to the line object', () => {
+    const side = {
+      discussions: [{}],
+      discussionsExpanded: true,
+      hasForm: true,
+    };
+    const content = {
+      diffFile: {},
+      hasParallelDraftLeft: () => false,
+      hasParallelDraftRight: () => false,
+      draftForLine: () => ({}),
+    };
+    const line = { left: side, right: side };
+    const expectation = {
+      commentRowClasses: '',
+      draftRowClasses: 'js-temp-notes-holder',
+      hasDiscussionsLeft: true,
+      hasDiscussionsRight: true,
+      isContextLineLeft: false,
+      isContextLineRight: false,
+      isMatchLineLeft: false,
+      isMatchLineRight: false,
+      isMetaLineLeft: false,
+      isMetaLineRight: false,
+    };
+    const leftExpectation = {
+      renderDiscussion: true,
+      hasDraft: false,
+      lineDraft: {},
+      hasCommentForm: true,
+    };
+    const rightExpectation = {
+      renderDiscussion: false,
+      hasDraft: false,
+      lineDraft: {},
+      hasCommentForm: false,
+    };
+    const mapped = utils.mapParallel(content)(line);
+
+    expect(mapped).toMatchObject(expectation);
+    expect(mapped.left).toMatchObject(leftExpectation);
+    expect(mapped.right).toMatchObject(rightExpectation);
+  });
+});
+
+describe('mapInline', () => {
+  it('should assign computed properties to the line object', () => {
+    const content = {
+      diffFile: {},
+      shouldRenderDraftRow: () => false,
+    };
+    const line = {
+      discussions: [{}],
+      discussionsExpanded: true,
+      hasForm: true,
+    };
+    const expectation = {
+      commentRowClasses: '',
+      hasDiscussions: true,
+      isContextLine: false,
+      isMatchLine: false,
+      isMetaLine: false,
+      renderDiscussion: true,
+      hasDraft: false,
+      hasCommentForm: true,
+    };
+    const mapped = utils.mapInline(content)(line);
+
+    expect(mapped).toMatchObject(expectation);
+  });
+});
diff --git a/spec/frontend/diffs/components/diff_view_spec.js b/spec/frontend/diffs/components/diff_view_spec.js
new file mode 100644
index 00000000000..4d90112d8f6
--- /dev/null
+++ b/spec/frontend/diffs/components/diff_view_spec.js
@@ -0,0 +1,82 @@
+import { shallowMount, createLocalVue } from '@vue/test-utils';
+import Vuex from 'vuex';
+import DiffView from '~/diffs/components/diff_view.vue';
+// import DraftNote from '~/batch_comments/components/draft_note.vue';
+// import DiffRow from '~/diffs/components/diff_row.vue';
+// import DiffCommentCell from '~/diffs/components/diff_comment_cell.vue';
+// import DiffExpansionCell from '~/diffs/components/diff_expansion_cell.vue';
+
+describe('DiffView', () => {
+  const DiffExpansionCell = { template: `<div/>` };
+  const DiffRow = { template: `<div/>` };
+  const DiffCommentCell = { template: `<div/>` };
+  const DraftNote = { template: `<div/>` };
+  const createWrapper = props => {
+    const localVue = createLocalVue();
+    localVue.use(Vuex);
+
+    const batchComments = {
+      getters: {
+        shouldRenderDraftRow: () => false,
+        shouldRenderParallelDraftRow: () => () => true,
+        draftForLine: () => false,
+        draftsForFile: () => false,
+        hasParallelDraftLeft: () => false,
+        hasParallelDraftRight: () => false,
+      },
+      namespaced: true,
+    };
+    const diffs = { getters: { commitId: () => 'abc123' }, namespaced: true };
+    const notes = {
+      state: { selectedCommentPosition: null, selectedCommentPositionHover: null },
+    };
+
+    const store = new Vuex.Store({
+      modules: { diffs, notes, batchComments },
+    });
+
+    const propsData = {
+      diffFile: {},
+      diffLines: [],
+      ...props,
+    };
+    const stubs = { DiffExpansionCell, DiffRow, DiffCommentCell, DraftNote };
+    return shallowMount(DiffView, { propsData, store, localVue, stubs });
+  };
+
+  it('renders a match line', () => {
+    const wrapper = createWrapper({ diffLines: [{ isMatchLineLeft: true }] });
+    expect(wrapper.find(DiffExpansionCell).exists()).toBe(true);
+  });
+
+  it.each`
+    type          | side       | container | sides                                                    | total
+    ${'parallel'} | ${'left'}  | ${'.old'} | ${{ left: { lineDraft: {} }, right: { lineDraft: {} } }} | ${2}
+    ${'parallel'} | ${'right'} | ${'.new'} | ${{ left: { lineDraft: {} }, right: { lineDraft: {} } }} | ${2}
+    ${'inline'}   | ${'left'}  | ${'.old'} | ${{ left: { lineDraft: {} } }}                           | ${1}
+    ${'inline'}   | ${'right'} | ${'.new'} | ${{ right: { lineDraft: {} } }}                          | ${1}
+    ${'inline'}   | ${'left'}  | ${'.old'} | ${{ left: { lineDraft: {} }, right: { lineDraft: {} } }} | ${1}
+  `(
+    'renders a $type comment row with comment cell on $side',
+    ({ type, container, sides, total }) => {
+      const wrapper = createWrapper({
+        diffLines: [{ renderCommentRow: true, ...sides }],
+        inline: type === 'inline',
+      });
+      expect(wrapper.findAll(DiffCommentCell).length).toBe(total);
+      expect(
+        wrapper
+          .find(container)
+          .find(DiffCommentCell)
+          .exists(),
+      ).toBe(true);
+    },
+  );
+
+  it('renders a draft row', () => {
+    const wrapper = createWrapper({
+      diffLines: [{ renderCommentRow: true, left: { lineDraft: { isDraft: true } } }],
+    });
+    expect(wrapper.find(DraftNote).exists()).toBe(true);
+  });
+});
diff --git a/spec/frontend/diffs/components/inline_diff_expansion_row_spec.js b/spec/frontend/diffs/components/inline_diff_expansion_row_spec.js
deleted file mode 100644
index 81e5403d502..00000000000
--- a/spec/frontend/diffs/components/inline_diff_expansion_row_spec.js
+++ /dev/null
@@ -1,32 +0,0 @@
-import Vue from 'vue';
-import { createComponentWithStore } from 'helpers/vue_mount_component_helper';
-import { createStore } from '~/mr_notes/stores';
-import InlineDiffExpansionRow from '~/diffs/components/inline_diff_expansion_row.vue';
-import diffFileMockData from '../mock_data/diff_file';
-
-describe('InlineDiffExpansionRow', () => {
-  const mockData = { ...diffFileMockData };
-  const matchLine = mockData.highlighted_diff_lines.pop();
-
-  const createComponent = (options = {}) => {
-    const cmp = Vue.extend(InlineDiffExpansionRow);
-    const defaults = {
-      fileHash: mockData.file_hash,
-      contextLinesPath: 'contextLinesPath',
-      line: matchLine,
-      isTop: false,
-      isBottom: false,
-    };
-    const props = { ...defaults, ...options };
-
-    return createComponentWithStore(cmp, createStore(), props).$mount();
-  };
-
-  describe('template', () => {
-    it('should render expansion row for match lines', () => {
-      const vm = createComponent();
-
-      expect(vm.$el.classList.contains('line_expansion')).toBe(true);
-    });
-  });
-});
diff --git a/spec/frontend/diffs/components/inline_diff_table_row_spec.js b/spec/frontend/diffs/components/inline_diff_table_row_spec.js
index c65a39b9083..21e7d7397a0 100644
--- a/spec/frontend/diffs/components/inline_diff_table_row_spec.js
+++ b/spec/frontend/diffs/components/inline_diff_table_row_spec.js
@@ -4,6 +4,7 @@ import InlineDiffTableRow from '~/diffs/components/inline_diff_table_row.vue';
 import DiffGutterAvatars from '~/diffs/components/diff_gutter_avatars.vue';
 import diffFileMockData from '../mock_data/diff_file';
 import discussionsMockData from '../mock_data/diff_discussions';
+import { mapInline } from '~/diffs/components/diff_row_utils';
 
 const TEST_USER_ID = 'abc123';
 const TEST_USER = { id: TEST_USER_ID };
@@ -11,7 +12,16 @@ const TEST_USER = { id: TEST_USER_ID };
 describe('InlineDiffTableRow', () => {
   let wrapper;
   let store;
-  const thisLine = diffFileMockData.highlighted_diff_lines[0];
+  const mockDiffContent = {
+    diffFile: diffFileMockData,
+    shouldRenderDraftRow: jest.fn(),
+    hasParallelDraftLeft: jest.fn(),
+    hasParallelDraftRight: jest.fn(),
+    draftForLine: jest.fn(),
+  };
+
+  const applyMap = mapInline(mockDiffContent);
+  const thisLine = applyMap(diffFileMockData.highlighted_diff_lines[0]);
 
   const createComponent = (props = {}, propsStore = store) => {
     wrapper = shallowMount(InlineDiffTableRow, {
@@ -132,7 +142,7 @@ describe('InlineDiffTableRow', () => {
         ${true}  | ${{ ...thisLine, type: 'old-nonewline', discussions: [] }} | ${false}
         ${true}  | ${{ ...thisLine, discussions: [{}] }}                      | ${false}
       `('visible is $expectation - line ($line)', ({ isHover, line, expectation }) => {
-        createComponent({ line });
+        createComponent({ line: applyMap(line) });
         wrapper.setData({ isHover });
 
         return wrapper.vm.$nextTick().then(() => {
@@ -148,7 +158,7 @@ describe('InlineDiffTableRow', () => {
         'has attribute disabled=$disabled when the outer component has prop commentsDisabled=$commentsDisabled',
         ({ disabled, commentsDisabled }) => {
           createComponent({
-            line: { ...thisLine, commentsDisabled },
+            line: applyMap({ ...thisLine, commentsDisabled }),
           });
 
           wrapper.setData({ isHover: true });
@@ -177,7 +187,7 @@ describe('InlineDiffTableRow', () => {
         'has the correct tooltip when commentsDisabled=$commentsDisabled',
         ({ tooltip, commentsDisabled }) => {
           createComponent({
-            line: { ...thisLine, commentsDisabled },
+            line: applyMap({ ...thisLine, commentsDisabled }),
           });
 
           wrapper.setData({ isHover: true });
@@ -216,7 +226,7 @@ describe('InlineDiffTableRow', () => {
             beforeEach(() => {
               jest.spyOn(store, 'dispatch').mockImplementation();
               createComponent({
-                line: { ...thisLine, ...lineProps },
+                line: applyMap({ ...thisLine, ...lineProps }),
               });
             });
 
@@ -268,7 +278,7 @@ describe('InlineDiffTableRow', () => {
 
       describe('with showCommentButton', () => {
         it('renders if line has discussions', () => {
-          createComponent({ line });
+          createComponent({ line: applyMap(line) });
 
           expect(findAvatars().props()).toEqual({
             discussions: line.discussions,
@@ -278,13 +288,13 @@ describe('InlineDiffTableRow', () => {
 
         it('does notrender if line has no discussions', () => {
           line.discussions = [];
-          createComponent({ line });
+          createComponent({ line: applyMap(line) });
 
           expect(findAvatars().exists()).toEqual(false);
         });
 
         it('toggles line discussion', () => {
-          createComponent({ line });
+          createComponent({ line: applyMap(line) });
 
           expect(store.dispatch).toHaveBeenCalledTimes(1);
 
diff --git a/spec/frontend/diffs/components/inline_diff_view_spec.js b/spec/frontend/diffs/components/inline_diff_view_spec.js
index 39c581e2796..6a1791509fd 100644
--- a/spec/frontend/diffs/components/inline_diff_view_spec.js
+++ b/spec/frontend/diffs/components/inline_diff_view_spec.js
@@ -1,54 +1,57 @@
-import Vue from 'vue';
 import '~/behaviors/markdown/render_gfm';
-import { createComponentWithStore } from 'helpers/vue_mount_component_helper';
+import { mount } from '@vue/test-utils';
+import { getByText } from '@testing-library/dom';
 import { createStore } from '~/mr_notes/stores';
 import InlineDiffView from '~/diffs/components/inline_diff_view.vue';
+import { mapInline } from '~/diffs/components/diff_row_utils';
 import diffFileMockData from '../mock_data/diff_file';
 import discussionsMockData from '../mock_data/diff_discussions';
 
 describe('InlineDiffView', () => {
-  let component;
+  let wrapper;
   const getDiffFileMock = () => ({ ...diffFileMockData });
   const getDiscussionsMockData = () => [{ ...discussionsMockData }];
   const notesLength = getDiscussionsMockData()[0].notes.length;
 
-  beforeEach(done => {
-    const diffFile = getDiffFileMock();
+  const setup = (diffFile, diffLines) => {
+    const mockDiffContent = {
+      diffFile,
+      shouldRenderDraftRow: jest.fn(),
+    };
 
     const store = createStore();
 
     store.dispatch('diffs/setInlineDiffViewType');
-    component = createComponentWithStore(Vue.extend(InlineDiffView), store, {
-      diffFile,
-      diffLines: diffFile.highlighted_diff_lines,
-    }).$mount();
-
-    Vue.nextTick(done);
-  });
+    wrapper = mount(InlineDiffView, {
+      store,
+      propsData: {
+        diffFile,
+        diffLines: diffLines.map(mapInline(mockDiffContent)),
+      },
+    });
+  };
 
   describe('template', () => {
     it('should have rendered diff lines', () => {
-      const el = component.$el;
+      const diffFile = getDiffFileMock();
+      setup(diffFile, diffFile.highlighted_diff_lines);
 
-      expect(el.querySelectorAll('tr.line_holder').length).toEqual(8);
-      expect(el.querySelectorAll('tr.line_holder.new').length).toEqual(4);
-      expect(el.querySelectorAll('tr.line_expansion.match').length).toEqual(1);
-      expect(el.textContent.indexOf('Bad dates')).toBeGreaterThan(-1);
+      expect(wrapper.findAll('tr.line_holder').length).toEqual(8);
+      expect(wrapper.findAll('tr.line_holder.new').length).toEqual(4);
+      expect(wrapper.findAll('tr.line_expansion.match').length).toEqual(1);
+      getByText(wrapper.element, /Bad dates/i);
     });
 
-    it('should render discussions', done => {
-      const el = component.$el;
-      component.diffLines[1].discussions = getDiscussionsMockData();
-      component.diffLines[1].discussionsExpanded = true;
-
-      Vue.nextTick(() => {
-        expect(el.querySelectorAll('.notes_holder').length).toEqual(1);
-        expect(el.querySelectorAll('.notes_holder .note').length).toEqual(notesLength + 1);
-        expect(el.innerText.indexOf('comment 5')).toBeGreaterThan(-1);
-        component.$store.dispatch('setInitialNotes', []);
+    it('should render discussions', () => {
+      const diffFile = getDiffFileMock();
+      diffFile.highlighted_diff_lines[1].discussions = getDiscussionsMockData();
+      diffFile.highlighted_diff_lines[1].discussionsExpanded = true;
+      setup(diffFile, diffFile.highlighted_diff_lines);
 
-        done();
-      });
+      expect(wrapper.findAll('.notes_holder').length).toEqual(1);
+      expect(wrapper.findAll('.notes_holder .note').length).toEqual(notesLength + 1);
+      getByText(wrapper.element, 'comment 5');
+      wrapper.vm.$store.dispatch('setInitialNotes', []);
     });
   });
 });
diff --git a/spec/frontend/diffs/components/parallel_diff_expansion_row_spec.js b/spec/frontend/diffs/components/parallel_diff_expansion_row_spec.js
deleted file mode 100644
index 38112445e8d..00000000000
--- a/spec/frontend/diffs/components/parallel_diff_expansion_row_spec.js
+++ /dev/null
@@ -1,31 +0,0 @@
-import Vue from 'vue';
-import { createComponentWithStore } from 'helpers/vue_mount_component_helper';
-import { createStore } from '~/mr_notes/stores';
-import ParallelDiffExpansionRow from '~/diffs/components/parallel_diff_expansion_row.vue';
-import diffFileMockData from '../mock_data/diff_file';
-
-describe('ParallelDiffExpansionRow', () => {
-  const matchLine = diffFileMockData.highlighted_diff_lines[5];
-
-  const createComponent = (options = {}) => {
-    const cmp = Vue.extend(ParallelDiffExpansionRow);
-    const defaults = {
-      fileHash: diffFileMockData.file_hash,
-      contextLinesPath: 'contextLinesPath',
-      line: matchLine,
-      isTop: false,
-      isBottom: false,
-    };
-    const props = { ...defaults, ...options };
-
-    return createComponentWithStore(cmp, createStore(), props).$mount();
-  };
-
-  describe('template', () => {
-    it('should render expansion row for match lines', () => {
-      const vm = createComponent();
-
-      expect(vm.$el.classList.contains('line_expansion')).toBe(true);
-    });
-  });
-});
diff --git a/spec/frontend/diffs/components/parallel_diff_table_row_spec.js b/spec/frontend/diffs/components/parallel_diff_table_row_spec.js
index 13031bd8b66..57eff177261 100644
--- a/spec/frontend/diffs/components/parallel_diff_table_row_spec.js
+++ b/spec/frontend/diffs/components/parallel_diff_table_row_spec.js
@@ -3,11 +3,22 @@ import { shallowMount } from '@vue/test-utils';
 import { createComponentWithStore } from 'helpers/vue_mount_component_helper';
 import { createStore } from '~/mr_notes/stores';
 import ParallelDiffTableRow from '~/diffs/components/parallel_diff_table_row.vue';
+import { mapParallel } from '~/diffs/components/diff_row_utils';
 import diffFileMockData from '../mock_data/diff_file';
 import DiffGutterAvatars from '~/diffs/components/diff_gutter_avatars.vue';
 import discussionsMockData from '../mock_data/diff_discussions';
 
 describe('ParallelDiffTableRow', () => {
+  const mockDiffContent = {
+    diffFile: diffFileMockData,
+    shouldRenderDraftRow: jest.fn(),
+    hasParallelDraftLeft: jest.fn(),
+    hasParallelDraftRight: jest.fn(),
+    draftForLine: jest.fn(),
+  };
+
+  const applyMap = mapParallel(mockDiffContent);
+
   describe('when one side is empty', () => {
     let wrapper;
     let vm;
@@ -18,7 +29,7 @@ describe('ParallelDiffTableRow', () => {
       wrapper = shallowMount(ParallelDiffTableRow, {
         store: createStore(),
         propsData: {
-          line: thisLine,
+          line: applyMap(thisLine),
           fileHash: diffFileMockData.file_hash,
           filePath: diffFileMockData.file_path,
           contextLinesPath: 'contextLinesPath',
@@ -67,7 +78,7 @@ describe('ParallelDiffTableRow', () => {
 
     beforeEach(() => {
       vm = createComponentWithStore(Vue.extend(ParallelDiffTableRow), createStore(), {
-        line: thisLine,
+        line: applyMap(thisLine),
         fileHash: diffFileMockData.file_hash,
         filePath: diffFileMockData.file_path,
         contextLinesPath: 'contextLinesPath',
@@ -243,7 +254,10 @@ describe('ParallelDiffTableRow', () => {
         ${{ ...thisLine, left: { type: 'old-nonewline', discussions: [] } }} | ${false}
         ${{ ...thisLine, left: { discussions: [{}] } }}                      | ${false}
       `('visible is $expectation - line ($line)', async ({ line, expectation }) => {
-        createComponent({ line }, store, { isLeftHover: true, isCommentButtonRendered: true });
+        createComponent({ line: applyMap(line) }, store, {
+          isLeftHover: true,
+          isCommentButtonRendered: true,
+        });
 
         expect(findNoteButton().isVisible()).toBe(expectation);
       });
@@ -320,7 +334,7 @@ describe('ParallelDiffTableRow', () => {
               Object.assign(thisLine.left, lineProps);
               Object.assign(thisLine.right, lineProps);
               createComponent({
-                line: { ...thisLine },
+                line: applyMap({ ...thisLine }),
               });
             });
 
@@ -357,7 +371,7 @@ describe('ParallelDiffTableRow', () => {
       beforeEach(() => {
         jest.spyOn(store, 'dispatch').mockImplementation();
 
-        line = {
+        line = applyMap({
           left: {
             line_code: TEST_LINE_CODE,
             type: 'new',
@@ -369,7 +383,7 @@ describe('ParallelDiffTableRow', () => {
             rich_text: '+<span id="LC1" class="line" lang="plaintext">  - Bad dates</span>\n',
             meta_data: null,
           },
-        };
+        });
       });
 
       describe('with showCommentButton', () => {
@@ -384,7 +398,7 @@ describe('ParallelDiffTableRow', () => {
 
         it('does notrender if line has no discussions', () => {
           line.left.discussions = [];
-          createComponent({ line });
+          createComponent({ line: applyMap(line) });
 
           expect(findAvatars().exists()).toEqual(false);
         });
diff --git a/spec/frontend/diffs/components/tree_list_spec.js b/spec/frontend/diffs/components/tree_list_spec.js
index cc177a81d88..c89403e4869 100644
--- a/spec/frontend/diffs/components/tree_list_spec.js
+++ b/spec/frontend/diffs/components/tree_list_spec.js
@@ -91,12 +91,12 @@ describe('Diffs tree list component', () => {
       expect(
         getFileRows()
           .at(0)
-          .text(),
+          .html(),
       ).toContain('index.js');
       expect(
         getFileRows()
           .at(1)
-          .text(),
+          .html(),
       ).toContain('app');
     });
 
@@ -138,7 +138,7 @@ describe('Diffs tree list component', () => {
       wrapper.vm.$store.state.diffs.renderTreeList = false;
 
       return wrapper.vm.$nextTick().then(() => {
-        expect(wrapper.find('.file-row').text()).toContain('index.js');
+        expect(wrapper.find('.file-row').html()).toContain('index.js');
       });
     });
   });
diff --git a/spec/frontend/diffs/mock_data/diff_file.js b/spec/frontend/diffs/mock_data/diff_file.js
index d3886819a91..cef776c885a 100644
--- a/spec/frontend/diffs/mock_data/diff_file.js
+++ b/spec/frontend/diffs/mock_data/diff_file.js
@@ -27,6 +27,7 @@ export default {
     name: 'text',
     error: null,
     automaticallyCollapsed: false,
+    manuallyCollapsed: null,
   },
   added_lines: 2,
   removed_lines: 0,
diff --git a/spec/frontend/diffs/mock_data/diff_file_unreadable.js b/spec/frontend/diffs/mock_data/diff_file_unreadable.js
index f6cdca9950a..2a5d694e3b8 100644
--- a/spec/frontend/diffs/mock_data/diff_file_unreadable.js
+++ b/spec/frontend/diffs/mock_data/diff_file_unreadable.js
@@ -26,6 +26,7 @@ export default {
     name: 'text',
     error: null,
     automaticallyCollapsed: false,
+    manuallyCollapsed: null,
   },
   added_lines: 0,
   removed_lines: 0,
diff --git a/spec/frontend/diffs/store/actions_spec.js b/spec/frontend/diffs/store/actions_spec.js
index c3e4ee9c531..0af5ddd9764 100644
--- a/spec/frontend/diffs/store/actions_spec.js
+++ b/spec/frontend/diffs/store/actions_spec.js
@@ -27,7 +27,6 @@ import {
   scrollToLineIfNeededInline,
   scrollToLineIfNeededParallel,
   loadCollapsedDiff,
-  expandAllFiles,
   toggleFileDiscussions,
   saveDiffDiscussion,
   setHighlightedRow,
@@ -42,7 +41,7 @@ import {
   fetchFullDiff,
   toggleFullDiff,
   switchToFullDiffFromRenamedFile,
-  setFileCollapsed,
+  setFileCollapsedByUser,
   setExpandedDiffLines,
   setSuggestPopoverDismissed,
   changeCurrentCommit,
@@ -658,23 +657,6 @@ describe('DiffsStoreActions', () => {
     });
   });
 
-  describe('expandAllFiles', () => {
-    it('should change the collapsed prop from the diffFiles', done => {
-      testAction(
-        expandAllFiles,
-        null,
-        {},
-        [
-          {
-            type: types.EXPAND_ALL_FILES,
-          },
-        ],
-        [],
-        done,
-      );
-    });
-  });
-
   describe('toggleFileDiscussions', () => {
     it('should dispatch collapseDiscussion when all discussions are expanded', () => {
       const getters = {
@@ -1167,7 +1149,11 @@ describe('DiffsStoreActions', () => {
       file_hash: 'testhash',
       alternate_viewer: { name: updatedViewerName },
     };
-    const updatedViewer = { name: updatedViewerName, automaticallyCollapsed: false };
+    const updatedViewer = {
+      name: updatedViewerName,
+      automaticallyCollapsed: false,
+      manuallyCollapsed: false,
+    };
     const testData = [{ rich_text: 'test' }, { rich_text: 'file2' }];
     let renamedFile;
     let mock;
@@ -1216,13 +1202,18 @@ describe('DiffsStoreActions', () => {
     });
   });
 
-  describe('setFileCollapsed', () => {
+  describe('setFileUserCollapsed', () => {
     it('commits SET_FILE_COLLAPSED', done => {
       testAction(
-        setFileCollapsed,
+        setFileCollapsedByUser,
         { filePath: 'test', collapsed: true },
         null,
-        [{ type: types.SET_FILE_COLLAPSED, payload: { filePath: 'test', collapsed: true } }],
+        [
+          {
+            type: types.SET_FILE_COLLAPSED,
+            payload: { filePath: 'test', collapsed: true, trigger: 'manual' },
+          },
+        ],
         [],
         done,
       );
diff --git a/spec/frontend/diffs/store/getters_spec.js b/spec/frontend/diffs/store/getters_spec.js
index 0083f1d8b44..7e936c561fc 100644
--- a/spec/frontend/diffs/store/getters_spec.js
+++ b/spec/frontend/diffs/store/getters_spec.js
@@ -49,23 +49,53 @@ describe('Diffs Module Getters', () => {
     });
   });
 
-  describe('hasCollapsedFile', () => {
-    it('returns true when all files are collapsed', () => {
-      localState.diffFiles = [
-        { viewer: { automaticallyCollapsed: true } },
-        { viewer: { automaticallyCollapsed: true } },
-      ];
+  describe('whichCollapsedTypes', () => {
+    const autoCollapsedFile = { viewer: { automaticallyCollapsed: true, manuallyCollapsed: null } };
+    const manuallyCollapsedFile = {
+      viewer: { automaticallyCollapsed: false, manuallyCollapsed: true },
+    };
+    const openFile = { viewer: { automaticallyCollapsed: false, manuallyCollapsed: false } };
+
+    it.each`
+      description                                 | value    | files
+      ${'all files are automatically collapsed'}  | ${true}  | ${[{ ...autoCollapsedFile }, { ...autoCollapsedFile }]}
+      ${'all files are manually collapsed'}       | ${true}  | ${[{ ...manuallyCollapsedFile }, { ...manuallyCollapsedFile }]}
+      ${'no files are collapsed in any way'}      | ${false} | ${[{ ...openFile }, { ...openFile }]}
+      ${'some files are collapsed in either way'} | ${true}  | ${[{ ...manuallyCollapsedFile }, { ...autoCollapsedFile }, { ...openFile }]}
+    `('`any` is $value when $description', ({ value, files }) => {
+      localState.diffFiles = files;
+
+      const getterResult = getters.whichCollapsedTypes(localState);
+
+      expect(getterResult.any).toEqual(value);
+    });
+
+    it.each`
+      description                                 | value    | files
+      ${'all files are automatically collapsed'}  | ${true}  | ${[{ ...autoCollapsedFile }, { ...autoCollapsedFile }]}
+      ${'all files are manually collapsed'}       | ${false} | ${[{ ...manuallyCollapsedFile }, { ...manuallyCollapsedFile }]}
+      ${'no files are collapsed in any way'}      | ${false} | ${[{ ...openFile }, { ...openFile }]}
+      ${'some files are collapsed in either way'} | ${true}  | ${[{ ...manuallyCollapsedFile }, { ...autoCollapsedFile }, { ...openFile }]}
+    `('`automatic` is $value when $description', ({ value, files }) => {
+      localState.diffFiles = files;
 
-      expect(getters.hasCollapsedFile(localState)).toEqual(true);
+      const getterResult = getters.whichCollapsedTypes(localState);
+
+      expect(getterResult.automatic).toEqual(value);
     });
 
-    it('returns true when at least one file is collapsed', () => {
-      localState.diffFiles = [
-        { viewer: { automaticallyCollapsed: false } },
-        { viewer: { automaticallyCollapsed: true } },
-      ];
+    it.each`
+      description                                 | value    | files
+      ${'all files are automatically collapsed'}  | ${false} | ${[{ ...autoCollapsedFile }, { ...autoCollapsedFile }]}
+      ${'all files are manually collapsed'}       | ${true}  | ${[{ ...manuallyCollapsedFile }, { ...manuallyCollapsedFile }]}
+      ${'no files are collapsed in any way'}      | ${false} | ${[{ ...openFile }, { ...openFile }]}
+      ${'some files are collapsed in either way'} | ${true}  | ${[{ ...manuallyCollapsedFile }, { ...autoCollapsedFile }, { ...openFile }]}
+    `('`manual` is $value when $description', ({ value, files }) => {
+      localState.diffFiles = files;
+
+      const getterResult = getters.whichCollapsedTypes(localState);
 
-      expect(getters.hasCollapsedFile(localState)).toEqual(true);
+      expect(getterResult.manual).toEqual(value);
     });
   });
 
diff --git a/spec/frontend/diffs/store/mutations_spec.js b/spec/frontend/diffs/store/mutations_spec.js
index a84ad63c695..c0645faf89e 100644
--- a/spec/frontend/diffs/store/mutations_spec.js
+++ b/spec/frontend/diffs/store/mutations_spec.js
@@ -126,21 +126,6 @@ describe('DiffsStoreMutations', () => {
     });
   });
 
-  describe('EXPAND_ALL_FILES', () => {
-    it('should change the collapsed prop from diffFiles', () => {
-      const diffFile = {
-        viewer: {
-          automaticallyCollapsed: true,
-        },
-      };
-      const state = { expandAllFiles: true, diffFiles: [diffFile] };
-
-      mutations[types.EXPAND_ALL_FILES](state);
-
-      expect(state.diffFiles[0].viewer.automaticallyCollapsed).toEqual(false);
-    });
-  });
-
   describe('ADD_CONTEXT_LINES', () => {
     it('should call utils.addContextLines with proper params', () => {
       const options = {
diff --git a/spec/frontend/diffs/store/utils_spec.js b/spec/frontend/diffs/store/utils_spec.js
index 39a482c85ae..866be0abd22 100644
--- a/spec/frontend/diffs/store/utils_spec.js
+++ b/spec/frontend/diffs/store/utils_spec.js
@@ -1221,5 +1221,26 @@ describe('DiffsStoreUtils', () => {
         file.parallel_diff_lines,
       );
     });
+
+    /**
+     * What's going on here?
+     *
+     * The inline version of parallelizeDiffLines simply keeps the difflines
+     * in the same order they are received as opposed to shuffling them
+     * to be "side by side".
+     *
+     * This keeps the underlying data structure the same which simplifies
+     * the components, but keeps the changes grouped together as users
+     * expect when viewing changes inline.
+     */
+    it('converts inline diff lines to inline diff lines with a parallel structure', () => {
+      const file = getDiffFileMock();
+      const files = utils.parallelizeDiffLines(file.highlighted_diff_lines, true);
+
+      expect(files[5].left).toEqual(file.parallel_diff_lines[5].left);
+      expect(files[5].right).toBeNull();
+      expect(files[6].left).toBeNull();
+      expect(files[6].right).toEqual(file.parallel_diff_lines[5].right);
+    });
   });
 });