Add inline file coverage view for merge request diffs

app/assets/javascripts/diffs/components/app.vue

@@ -50,6 +50,11 @@ export default {
       type: String,
       required: true,
     },
+    endpointCoverage: {
+      type: String,
+      required: false,
+      default: '',
+    },
     projectPath: {
       type: String,
       required: true,
@@ -169,6 +174,7 @@ export default {
       endpoint: this.endpoint,
       endpointMetadata: this.endpointMetadata,
       endpointBatch: this.endpointBatch,
+      endpointCoverage: this.endpointCoverage,
       projectPath: this.projectPath,
       dismissEndpoint: this.dismissEndpoint,
       showSuggestPopover: this.showSuggestPopover,
@@ -218,6 +224,7 @@ export default {
       'fetchDiffFiles',
       'fetchDiffFilesMeta',
       'fetchDiffFilesBatch',
+      'fetchCoverageFiles',
       'startRenderDiffsQueue',
       'assignDiscussionsToDiff',
       'setHighlightedRow',
@@ -292,6 +299,10 @@ export default {
           });
       }
 
+      if (this.endpointCoverage) {
+        this.fetchCoverageFiles();
+      }
+
       if (!this.isNotesFetched) {
         eventHub.$emit('fetchNotesData');
       }

app/assets/javascripts/diffs/components/diff_expansion_cell.vue

@@ -54,7 +54,7 @@ export default {
     colspan: {
       type: Number,
       required: false,
-      default: 3,
+      default: 4,
     },
   },
   computed: {

app/assets/javascripts/diffs/components/inline_diff_comment_row.vue

@@ -51,7 +51,7 @@ export default {
 
 <template>
   <tr v-if="shouldRender" :class="className" class="notes_holder">
-    <td class="notes-content" colspan="3">
+    <td class="notes-content" colspan="4">
       <div class="content">
         <diff-discussions
           v-if="line.discussions.length"

app/assets/javascripts/diffs/components/inline_diff_table_row.vue

 <script>
-import { mapActions, mapState } from 'vuex';
+import { mapActions, mapGetters, mapState } from 'vuex';
+import { GlTooltipDirective } from '@gitlab/ui';
 import DiffTableCell from './diff_table_cell.vue';
 import {
   MATCH_LINE_TYPE,
@@ -15,11 +16,18 @@ export default {
   components: {
     DiffTableCell,
   },
+  directives: {
+    GlTooltip: GlTooltipDirective,
+  },
   props: {
     fileHash: {
       type: String,
       required: true,
     },
+    filePath: {
+      type: String,
+      required: true,
+    },
     contextLinesPath: {
       type: String,
       required: true,
@@ -40,6 +48,7 @@ export default {
     };
   },
   computed: {
+    ...mapGetters('diffs', ['fileLineCoverage']),
     ...mapState({
       isHighlighted(state) {
         return this.line.line_code !== null && this.line.line_code === state.diffs.highlightedRow;
@@ -62,6 +71,9 @@ export default {
     isMatchLine() {
       return this.line.type === MATCH_LINE_TYPE;
     },
+    coverageState() {
+      return this.fileLineCoverage(this.filePath, this.line.new_line);
+    },
   },
   created() {
     this.newLineType = NEW_LINE_TYPE;
@@ -113,6 +125,12 @@ export default {
       :is-highlighted="isHighlighted"
       class="diff-line-num new_line qa-new-diff-line"
     />
+    <td
+      v-gl-tooltip.hover
+      :title="coverageState.text"
+      :class="[line.type, coverageState.class, { hll: isHighlighted }]"
+      class="line-coverage"
+    ></td>
     <td
       :class="[
         line.type,
@@ -120,7 +138,7 @@ export default {
           hll: isHighlighted,
         },
       ]"
-      class="line_content"
+      class="line_content with-coverage"
       v-html="line.rich_text"
     ></td>
   </tr>

app/assets/javascripts/diffs/components/inline_diff_view.vue

@@ -48,6 +48,7 @@ export default {
     <colgroup>
       <col style="width: 50px;" />
       <col style="width: 50px;" />
+      <col style="width: 8px;" />
       <col />
     </colgroup>
     <tbody>
@@ -63,6 +64,7 @@ export default {
         <inline-diff-table-row
           :key="`${line.line_code || index}`"
           :file-hash="diffFile.file_hash"
+          :file-path="diffFile.file_path"
           :context-lines-path="diffFile.context_lines_path"
           :line="line"
           :is-bottom="index + 1 === diffLinesLength"

app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue

@@ -122,7 +122,7 @@ export default {
 
 <template>
   <tr v-if="shouldRender" :class="className" class="notes_holder">
-    <td class="notes-content parallel old" colspan="2">
+    <td class="notes-content parallel old" colspan="3">
       <div v-if="shouldRenderDiscussionsOnLeft" class="content">
         <diff-discussions
           :discussions="line.left.discussions"
@@ -147,7 +147,7 @@ export default {
         </template>
       </diff-discussion-reply>
     </td>
-    <td class="notes-content parallel new" colspan="2">
+    <td class="notes-content parallel new" colspan="3">
       <div v-if="shouldRenderDiscussionsOnRight" class="content">
         <diff-discussions
           :discussions="line.right.discussions"

app/assets/javascripts/diffs/components/parallel_diff_expansion_row.vue

@@ -49,7 +49,7 @@ export default {
         :line="line.left"
         :is-top="isTop"
         :is-bottom="isBottom"
-        :colspan="4"
+        :colspan="6"
       />
     </template>
   </tr>

app/assets/javascripts/diffs/components/parallel_diff_table_row.vue

 <script>
-import { mapActions, mapState } from 'vuex';
+import { mapActions, mapGetters, mapState } from 'vuex';
 import $ from 'jquery';
+import { GlTooltipDirective } from '@gitlab/ui';
 import DiffTableCell from './diff_table_cell.vue';
 import {
   MATCH_LINE_TYPE,
@@ -18,11 +19,18 @@ export default {
   components: {
     DiffTableCell,
   },
+  directives: {
+    GlTooltip: GlTooltipDirective,
+  },
   props: {
     fileHash: {
       type: String,
       required: true,
     },
+    filePath: {
+      type: String,
+      required: true,
+    },
     contextLinesPath: {
       type: String,
       required: true,
@@ -44,6 +52,7 @@ export default {
     };
   },
   computed: {
+    ...mapGetters('diffs', ['fileLineCoverage']),
     ...mapState({
       isHighlighted(state) {
         const lineCode =
@@ -82,6 +91,9 @@ export default {
     isMatchLineRight() {
       return this.line.right && this.line.right.type === MATCH_LINE_TYPE;
     },
+    coverageState() {
+      return this.fileLineCoverage(this.filePath, this.line.right.new_line);
+    },
   },
   created() {
     this.newLineType = NEW_LINE_TYPE;
@@ -99,7 +111,7 @@ export default {
       const allCellsInHoveringRow = Array.from(e.currentTarget.children);
       const hoverIndex = allCellsInHoveringRow.indexOf(hoveringCell);
 
-      if (hoverIndex >= 2) {
+      if (hoverIndex >= 3) {
         this.isRightHover = isHover;
       } else {
         this.isLeftHover = isHover;
@@ -143,17 +155,19 @@ export default {
         line-position="left"
         class="diff-line-num old_line"
       />
+      <td :class="parallelViewLeftLineType" class="line-coverage left-side"></td>
       <td
         :id="line.left.line_code"
         :class="parallelViewLeftLineType"
-        class="line_content parallel left-side"
+        class="line_content with-coverage parallel left-side"
         @mousedown="handleParallelLineMouseDown"
         v-html="line.left.rich_text"
       ></td>
     </template>
     <template v-else>
       <td class="diff-line-num old_line empty-cell"></td>
-      <td class="line_content parallel left-side empty-cell"></td>
+      <td class="line-coverage left-side empty-cell"></td>
+      <td class="line_content with-coverage parallel left-side empty-cell"></td>
     </template>
     <template v-if="line.right && !isMatchLineRight">
       <diff-table-cell
@@ -169,6 +183,12 @@ export default {
         line-position="right"
         class="diff-line-num new_line"
       />
+      <td
+        v-gl-tooltip.hover
+        :title="coverageState.text"
+        :class="[line.right.type, coverageState.class, { hll: isHighlighted }]"
+        class="line-coverage right-side"
+      ></td>
       <td
         :id="line.right.line_code"
         :class="[
@@ -177,14 +197,15 @@ export default {
             hll: isHighlighted,
           },
         ]"
-        class="line_content parallel right-side"
+        class="line_content with-coverage parallel right-side"
         @mousedown="handleParallelLineMouseDown"
         v-html="line.right.rich_text"
       ></td>
     </template>
     <template v-else>
       <td class="diff-line-num old_line empty-cell"></td>
-      <td class="line_content parallel right-side empty-cell"></td>
+      <td class="line-coverage right-side empty-cell"></td>
+      <td class="line_content with-coverage parallel right-side empty-cell"></td>
     </template>
   </tr>
 </template>

app/assets/javascripts/diffs/components/parallel_diff_view.vue

@@ -47,8 +47,10 @@ export default {
   >
     <colgroup>
       <col style="width: 50px;" />
+      <col style="width: 8px;" />
       <col />
       <col style="width: 50px;" />
+      <col style="width: 8px;" />
       <col />
     </colgroup>
     <tbody>
@@ -64,6 +66,7 @@ export default {
         <parallel-diff-table-row
           :key="line.line_code"
           :file-hash="diffFile.file_hash"
+          :file-path="diffFile.file_path"
           :context-lines-path="diffFile.context_lines_path"
           :line="line"
           :is-bottom="index + 1 === diffLinesLength"

app/assets/javascripts/diffs/index.js

@@ -69,6 +69,7 @@ export default function initDiffsApp(store) {
         endpoint: dataset.endpoint,
         endpointMetadata: dataset.endpointMetadata || '',
         endpointBatch: dataset.endpointBatch || '',
+        endpointCoverage: dataset.endpointCoverage || '',
         projectPath: dataset.projectPath,
         helpPagePath: dataset.helpPagePath,
         currentUser: JSON.parse(dataset.currentUserData) || {},
@@ -104,6 +105,7 @@ export default function initDiffsApp(store) {
           endpoint: this.endpoint,
           endpointMetadata: this.endpointMetadata,
           endpointBatch: this.endpointBatch,
+          endpointCoverage: this.endpointCoverage,
           currentUser: this.currentUser,
           projectPath: this.projectPath,
           helpPagePath: this.helpPagePath,

app/assets/javascripts/diffs/store/actions.js

 import Vue from 'vue';
 import Cookies from 'js-cookie';
+import Poll from '~/lib/utils/poll';
 import axios from '~/lib/utils/axios_utils';
+import httpStatusCodes from '~/lib/utils/http_status';
 import createFlash from '~/flash';
-import { s__ } from '~/locale';
+import { __, s__ } from '~/locale';
 import { handleLocationHash, historyPushState, scrollToElement } from '~/lib/utils/common_utils';
 import { mergeUrlParams, getLocationHash } from '~/lib/utils/url_utility';
 import TreeWorker from '../workers/tree_worker';
@@ -43,6 +45,7 @@ export const setBaseConfig = ({ commit }, options) => {
     endpoint,
     endpointMetadata,
     endpointBatch,
+    endpointCoverage,
     projectPath,
     dismissEndpoint,
     showSuggestPopover,
@@ -52,6 +55,7 @@ export const setBaseConfig = ({ commit }, options) => {
     endpoint,
     endpointMetadata,
     endpointBatch,
+    endpointCoverage,
     projectPath,
     dismissEndpoint,
     showSuggestPopover,
@@ -170,6 +174,26 @@ export const fetchDiffFilesMeta = ({ commit, state }) => {
     .catch(() => worker.terminate());
 };
 
+export const fetchCoverageFiles = ({ commit, state }) => {
+  const coveragePoll = new Poll({
+    resource: {
+      getCoverageReports: endpoint => axios.get(endpoint),
+    },
+    data: state.endpointCoverage,
+    method: 'getCoverageReports',
+    successCallback: ({ status, data }) => {
+      if (status === httpStatusCodes.OK) {
+        commit(types.SET_COVERAGE_DATA, data);
+
+        coveragePoll.stop();
+      }
+    },
+    errorCallback: () => createFlash(__('Something went wrong on our end. Please try again!')),
+  });
+
+  coveragePoll.makeRequest();
+};
+
 export const setHighlightedRow = ({ commit }, lineCode) => {
   const fileHash = lineCode.split('_')[0];
   commit(types.SET_HIGHLIGHTED_ROW, lineCode);

app/assets/javascripts/diffs/store/getters.js

+import { __, n__ } from '~/locale';
 import { PARALLEL_DIFF_VIEW_TYPE, INLINE_DIFF_VIEW_TYPE } from '../constants';
 
 export const isParallelView = state => state.diffViewType === PARALLEL_DIFF_VIEW_TYPE;
@@ -98,6 +99,29 @@ export const allBlobs = (state, getters) =>
 export const getCommentFormForDiffFile = state => fileHash =>
   state.commentForms.find(form => form.fileHash === fileHash);
 
+/**
+ * Returns the test coverage hits for a specific line of a given file
+ * @param {string} file
+ * @param {number} line
+ * @returns {number}
+ */
+export const fileLineCoverage = state => (file, line) => {
+  if (!state.coverageFiles.files) return {};
+  const fileCoverage = state.coverageFiles.files[file];
+  if (!fileCoverage) return {};
+  const lineCoverage = fileCoverage[String(line)];
+
+  if (lineCoverage === 0) {
+    return { text: __('No test coverage'), class: 'no-coverage' };
+  } else if (lineCoverage >= 0) {
+    return {
+      text: n__('Test coverage: %d hit', 'Test coverage: %d hits', lineCoverage),
+      class: 'coverage',
+    };
+  }
+  return {};
+};
+
 /**
  * Returns index of a currently selected diff in diffFiles
  * @returns {number}

app/assets/javascripts/diffs/store/modules/diff_state.js

@@ -17,6 +17,7 @@ export default () => ({
   commit: null,
   startVersion: null,
   diffFiles: [],
+  coverageFiles: {},
   mergeRequestDiffs: [],
   mergeRequestDiff: null,
   diffViewType: viewTypeFromQueryString || viewTypeFromCookie || defaultViewType,

app/assets/javascripts/diffs/store/mutation_types.js

@@ -5,6 +5,7 @@ export const SET_RETRIEVING_BATCHES = 'SET_RETRIEVING_BATCHES';
 export const SET_DIFF_DATA = 'SET_DIFF_DATA';
 export const SET_DIFF_DATA_BATCH = 'SET_DIFF_DATA_BATCH';
 export const SET_DIFF_VIEW_TYPE = 'SET_DIFF_VIEW_TYPE';
+export const SET_COVERAGE_DATA = 'SET_COVERAGE_DATA';
 export const SET_MERGE_REQUEST_DIFFS = 'SET_MERGE_REQUEST_DIFFS';
 export const TOGGLE_LINE_HAS_FORM = 'TOGGLE_LINE_HAS_FORM';
 export const ADD_CONTEXT_LINES = 'ADD_CONTEXT_LINES';

app/assets/javascripts/diffs/store/mutations.js

@@ -16,6 +16,7 @@ export default {
       endpoint,
       endpointMetadata,
       endpointBatch,
+      endpointCoverage,
       projectPath,
       dismissEndpoint,
       showSuggestPopover,
@@ -25,6 +26,7 @@ export default {
       endpoint,
       endpointMetadata,
       endpointBatch,
+      endpointCoverage,
       projectPath,
       dismissEndpoint,
       showSuggestPopover,
@@ -69,6 +71,10 @@ export default {
     });
   },
 
+  [types.SET_COVERAGE_DATA](state, coverageFiles) {
+    Object.assign(state, { coverageFiles });
+  },
+
   [types.RENDER_FILE](state, file) {
     Object.assign(file, {
       renderIt: true,

app/assets/stylesheets/highlight/common.scss

@@ -29,3 +29,15 @@
     color: $link;
   }
 }
+
+@mixin line-coverage-border-color($coverage, $no-coverage) {
+  transition: border-left 0.1s ease-out;
+
+  &.coverage {
+    border-left: 3px solid $coverage;
+  }
+
+  &.no-coverage {
+    border-left: 3px solid $no-coverage;
+  }
+}

app/assets/stylesheets/highlight/themes/dark.scss

@@ -24,6 +24,8 @@ $dark-pre-hll-bg: #373b41;
 $dark-hll-bg: #373b41;
 $dark-over-bg: #9f9ab5;
 $dark-expanded-bg: #3e3e3e;
+$dark-coverage: #b5bd68;
+$dark-no-coverage: #de935f;
 $dark-c: #969896;
 $dark-err: #c66;
 $dark-k: #b294bb;
@@ -124,12 +126,18 @@ $dark-il: #de935f;
     }
 
     td.diff-line-num.hll:not(.empty-cell),
+    td.line-coverage.hll:not(.empty-cell),
     td.line_content.hll:not(.empty-cell) {
       background-color: $dark-diff-not-empty-bg;
       border-color: darken($dark-diff-not-empty-bg, 15%);
     }
 
+    .line-coverage {
+      @include line-coverage-border-color($dark-coverage, $dark-no-coverage);
+    }
+
     .diff-line-num.new,
+    .line-coverage.new,
     .line_content.new {
       @include diff-background($dark-new-bg, $dark-new-idiff, $dark-border);
 
@@ -140,6 +148,7 @@ $dark-il: #de935f;
     }
 
     .diff-line-num.old,
+    .line-coverage.old,
     .line_content.old {
       @include diff-background($dark-old-bg, $dark-old-idiff, $dark-border);
 
@@ -168,6 +177,7 @@ $dark-il: #de935f;
     &:not(.diff-expanded) + .diff-expanded,
     &.diff-expanded + .line_holder:not(.diff-expanded) {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         border-top: 1px solid $black;
       }
@@ -175,6 +185,7 @@ $dark-il: #de935f;
 
     &.diff-expanded {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         background: $dark-expanded-bg;
         border-color: $dark-expanded-bg;

app/assets/stylesheets/highlight/themes/monokai.scss

@@ -17,6 +17,8 @@ $monokai-diff-border: #808080;
 $monokai-highlight-bg: #ffe792;
 $monokai-over-bg: #9f9ab5;
 $monokai-expanded-bg: #3e3e3e;
+$monokai-coverage: #a6e22e;
+$monokai-no-coverage: #fd971f;
 
 $monokai-new-bg: rgba(166, 226, 46, 0.1);
 $monokai-new-idiff: rgba(166, 226, 46, 0.15);
@@ -124,12 +126,18 @@ $monokai-gi: #a6e22e;
     }
 
     td.diff-line-num.hll:not(.empty-cell),
+    td.line-coverage.hll:not(.empty-cell),
     td.line_content.hll:not(.empty-cell) {
       background-color: $monokai-line-empty-bg;
       border-color: $monokai-line-empty-border;
     }
 
+    .line-coverage {
+      @include line-coverage-border-color($monokai-coverage, $monokai-no-coverage);
+    }
+
     .diff-line-num.new,
+    .line-coverage.new,
     .line_content.new {
       @include diff-background($monokai-new-bg, $monokai-new-idiff, $monokai-diff-border);
 
@@ -140,6 +148,7 @@ $monokai-gi: #a6e22e;
     }
 
     .diff-line-num.old,
+    .line-coverage.old,
     .line_content.old {
       @include diff-background($monokai-old-bg, $monokai-old-idiff, $monokai-diff-border);
 
@@ -168,6 +177,7 @@ $monokai-gi: #a6e22e;
     &:not(.diff-expanded) + .diff-expanded,
     &.diff-expanded + .line_holder:not(.diff-expanded) {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         border-top: 1px solid $black;
       }
@@ -175,6 +185,7 @@ $monokai-gi: #a6e22e;
 
     &.diff-expanded {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         background: $monokai-expanded-bg;
         border-color: $monokai-expanded-bg;

app/assets/stylesheets/highlight/themes/none.scss

@@ -51,6 +51,15 @@
       @include match-line;
     }
 
+    .line-coverage {
+      @include line-coverage-border-color($green-500, $orange-500);
+
+      &.old,
+      &.new {
+        background-color: $white-normal;
+      }
+    }
+
     .diff-line-num {
       &.old {
         a {
@@ -83,6 +92,7 @@
     &:not(.diff-expanded) + .diff-expanded,
     &.diff-expanded + .line_holder:not(.diff-expanded) {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         border-top: 1px solid $none-expanded-border;
       }
@@ -90,6 +100,7 @@
 
     &.diff-expanded {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         background: $none-expanded-bg;
         border-color: $none-expanded-bg;

app/assets/stylesheets/highlight/themes/solarized-dark.scss

@@ -21,6 +21,8 @@ $solarized-dark-highlight: #094554;
 $solarized-dark-hll-bg: #174652;
 $solarized-dark-over-bg: #9f9ab5;
 $solarized-dark-expanded-bg: #010d10;
+$solarized-dark-coverage: #859900;
+$solarized-dark-no-coverage: #cb4b16;
 $solarized-dark-c: #586e75;
 $solarized-dark-err: #93a1a1;
 $solarized-dark-g: #93a1a1;
@@ -128,12 +130,18 @@ $solarized-dark-il: #2aa198;
     }
 
     td.diff-line-num.hll:not(.empty-cell),
+    td.line-coverage.hll:not(.empty-cell),
     td.line_content.hll:not(.empty-cell) {
       background-color: $solarized-dark-hll-bg;
       border-color: darken($solarized-dark-hll-bg, 15%);
     }
 
+    .line-coverage {
+      @include line-coverage-border-color($solarized-dark-coverage, $solarized-dark-no-coverage);
+    }
+
     .diff-line-num.new,
+    .line-coverage.new,
     .line_content.new {
       @include diff-background($solarized-dark-new-bg, $solarized-dark-new-idiff, $solarized-dark-border);
 
@@ -144,6 +152,7 @@ $solarized-dark-il: #2aa198;
     }
 
     .diff-line-num.old,
+    .line-coverage.old,
     .line_content.old {
       @include diff-background($solarized-dark-old-bg, $solarized-dark-old-idiff, $solarized-dark-border);
 
@@ -172,6 +181,7 @@ $solarized-dark-il: #2aa198;
     &:not(.diff-expanded) + .diff-expanded,
     &.diff-expanded + .line_holder:not(.diff-expanded) {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         border-top: 1px solid $black;
       }
@@ -179,6 +189,7 @@ $solarized-dark-il: #2aa198;
 
     &.diff-expanded {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         background: $solarized-dark-expanded-bg;
         border-color: $solarized-dark-expanded-bg;

app/assets/stylesheets/highlight/themes/solarized-light.scss

@@ -23,6 +23,8 @@ $solarized-light-hll-bg: #ddd8c5;
 $solarized-light-over-bg: #ded7fc;
 $solarized-light-expanded-border: #d2cdbd;
 $solarized-light-expanded-bg: #ece6d4;
+$solarized-light-coverage: #859900;
+$solarized-light-no-coverage: #cb4b16;
 $solarized-light-c: #93a1a1;
 $solarized-light-err: #586e75;
 $solarized-light-g: #586e75;
@@ -135,12 +137,18 @@ $solarized-light-il: #2aa198;
     }
 
     td.diff-line-num.hll:not(.empty-cell),
+    td.line-coverage.hll:not(.empty-cell),
     td.line_content.hll:not(.empty-cell) {
       background-color: $solarized-light-hll-bg;
       border-color: darken($solarized-light-hll-bg, 15%);
     }
 
+    .line-coverage {
+      @include line-coverage-border-color($solarized-light-coverage, $solarized-light-no-coverage);
+    }
+
     .diff-line-num.new,
+    .line-coverage.new,
     .line_content.new {
       @include diff-background($solarized-light-new-bg,
       $solarized-light-new-idiff, $solarized-light-border);
@@ -152,6 +160,7 @@ $solarized-light-il: #2aa198;
     }
 
     .diff-line-num.old,
+    .line-coverage.old,
     .line_content.old {
       @include diff-background($solarized-light-old-bg, $solarized-light-old-idiff, $solarized-light-border);
 
@@ -180,6 +189,7 @@ $solarized-light-il: #2aa198;
     &:not(.diff-expanded) + .diff-expanded,
     &.diff-expanded + .line_holder:not(.diff-expanded) {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         border-top: 1px solid $solarized-light-expanded-border;
       }
@@ -187,6 +197,7 @@ $solarized-light-il: #2aa198;
 
     &.diff-expanded {
       > .diff-line-num,
+      > .line-coverage,
       > .line_content {
         background: $solarized-light-expanded-bg;
         border-color: $solarized-light-expanded-bg;

app/assets/stylesheets/highlight/white_base.scss

@@ -151,6 +151,7 @@ pre.code,
   &:not(.diff-expanded) + .diff-expanded,
   &.diff-expanded + .line_holder:not(.diff-expanded) {
     > .diff-line-num,
+    > .line-coverage,
     > .line_content {
       border-top: 1px solid $white-expanded-border;
     }
@@ -158,6 +159,7 @@ pre.code,
 
   &.diff-expanded {
     > .diff-line-num,
+    > .line-coverage,
     > .line_content {
       background: $white-expanded-bg;
       border-color: $white-expanded-bg;
@@ -197,6 +199,22 @@ pre.code,
       background-color: $line-select-yellow;
     }
   }
+
+  .line-coverage {
+    @include line-coverage-border-color($green-500, $orange-500);
+
+    &.old {
+      background-color: $line-removed;
+    }
+
+    &.new {
+      background-color: $line-added;
+    }
+
+    &.hll:not(.empty-cell) {
+      background-color: $line-select-yellow;
+    }
+  }
 }
 
 // highlight line via anchor

app/assets/stylesheets/pages/diff.scss

@@ -514,6 +514,10 @@ table.code {
           position: absolute;
           left: 0.5em;
         }
+
+        &.with-coverage::before {
+          left: 0;
+        }
       }
 
       &.new {
@@ -522,6 +526,10 @@ table.code {
           position: absolute;
           left: 0.5em;
         }
+
+        &.with-coverage::before {
+          left: 0;
+        }
       }
     }
   }

app/controllers/projects/merge_requests_controller.rb

@@ -14,7 +14,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
   skip_before_action :merge_request, only: [:index, :bulk_update]
   before_action :whitelist_query_limiting, only: [:assign_related_issues, :update]
   before_action :authorize_update_issuable!, only: [:close, :edit, :update, :remove_wip, :sort]
-  before_action :authorize_read_actual_head_pipeline!, only: [:test_reports, :exposed_artifacts]
+  before_action :authorize_read_actual_head_pipeline!, only: [:test_reports, :exposed_artifacts, :coverage_reports]
   before_action :set_issuables_index, only: [:index]
   before_action :authenticate_user!, only: [:assign_related_issues]
   before_action :check_user_can_push_to_source_branch!, only: [:rebase]
@@ -63,6 +63,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
         @issuable_sidebar = serializer.represent(@merge_request, serializer: 'sidebar')
         @current_user_data = UserSerializer.new(project: @project).represent(current_user, {}, MergeRequestUserEntity).to_json
         @show_whitespace_default = current_user.nil? || current_user.show_whitespace_in_diffs
+        @coverage_path = coverage_reports_project_merge_request_path(@project, @merge_request, format: :json) if @merge_request.has_coverage_reports?
 
         set_pipeline_variables
 
@@ -131,6 +132,14 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     reports_response(@merge_request.compare_test_reports)
   end
 
+  def coverage_reports
+    if @merge_request.has_coverage_reports?
+      reports_response(@merge_request.find_coverage_reports)
+    else
+      head :no_content
+    end
+  end
+
   def exposed_artifacts
     if @merge_request.has_exposed_artifacts?
       reports_response(@merge_request.find_exposed_artifacts)

app/models/ci/build.rb

@@ -916,6 +916,14 @@ module Ci
       end
     end
 
+    def collect_coverage_reports!(coverage_report)
+      each_report(Ci::JobArtifact::COVERAGE_REPORT_FILE_TYPES) do |file_type, blob|
+        Gitlab::Ci::Parsers.fabricate!(file_type).parse!(blob, coverage_report)
+      end
+
+      coverage_report
+    end
+
     def report_artifacts
       job_artifacts.with_reports
     end

app/models/ci/job_artifact.rb

@@ -11,6 +11,7 @@ module Ci
     NotSupportedAdapterError = Class.new(StandardError)
 
     TEST_REPORT_FILE_TYPES = %w[junit].freeze
+    COVERAGE_REPORT_FILE_TYPES = %w[cobertura].freeze
     NON_ERASABLE_FILE_TYPES = %w[trace].freeze
     DEFAULT_FILE_NAMES = {
       archive: nil,
@@ -29,7 +30,8 @@ module Ci
       performance: 'performance.json',
       metrics: 'metrics.txt',
       lsif: 'lsif.json',
-      dotenv: '.env'
+      dotenv: '.env',
+      cobertura: 'cobertura-coverage.xml'
     }.freeze
 
     INTERNAL_TYPES = {
@@ -45,6 +47,7 @@ module Ci
       network_referee: :gzip,
       lsif: :gzip,
       dotenv: :gzip,
+      cobertura: :gzip,
 
       # All these file formats use `raw` as we need to store them uncompressed
       # for Frontend to fetch the files and do analysis
@@ -92,6 +95,10 @@ module Ci
       with_file_types(TEST_REPORT_FILE_TYPES)
     end
 
+    scope :coverage_reports, -> do
+      with_file_types(COVERAGE_REPORT_FILE_TYPES)
+    end
+
     scope :erasable, -> do
       types = self.file_types.reject { |file_type| NON_ERASABLE_FILE_TYPES.include?(file_type) }.values
 
@@ -121,7 +128,8 @@ module Ci
       metrics_referee: 13, ## runner referees
       network_referee: 14, ## runner referees
       lsif: 15, # LSIF data for code navigation
-      dotenv: 16
+      dotenv: 16,
+      cobertura: 17
     }
 
     enum file_format: {

app/models/ci/pipeline.rb

@@ -820,6 +820,14 @@ module Ci
       end
     end
 
+    def coverage_reports
+      Gitlab::Ci::Reports::CoverageReports.new.tap do |coverage_reports|
+        builds.latest.with_reports(Ci::JobArtifact.coverage_reports).each do |build|
+          build.collect_coverage_reports!(coverage_reports)
+        end
+      end
+    end
+
     def has_exposed_artifacts?
       complete? && builds.latest.with_exposed_artifacts.exists?
     end

app/models/merge_request.rb

@@ -567,6 +567,10 @@ class MergeRequest < ApplicationRecord
     diffs.modified_paths
   end
 
+  def new_paths
+    diffs.diff_files.map(&:new_path)
+  end
+
   def diff_base_commit
     if merge_request_diff.persisted?
       merge_request_diff.base_commit
@@ -1295,6 +1299,24 @@ class MergeRequest < ApplicationRecord
     compare_reports(Ci::CompareTestReportsService)
   end
 
+  def has_coverage_reports?
+    return false unless Feature.enabled?(:coverage_report_view, project)
+
+    actual_head_pipeline&.has_reports?(Ci::JobArtifact.coverage_reports)
+  end
+
+  # TODO: this method and compare_test_reports use the same
+  # result type, which is handled by the controller's #reports_response.
+  # we should minimize mistakes by isolating the common parts.
+  # issue: https://gitlab.com/gitlab-org/gitlab/issues/34224
+  def find_coverage_reports
+    unless has_coverage_reports?
+      return { status: :error, status_reason: 'This merge request does not have coverage reports' }
+    end
+
+    compare_reports(Ci::GenerateCoverageReportsService)
+  end
+
   def has_exposed_artifacts?
     return false unless Feature.enabled?(:ci_expose_arbitrary_artifacts_in_mr, default_enabled: true)
 
@@ -1318,7 +1340,7 @@ class MergeRequest < ApplicationRecord
   # issue: https://gitlab.com/gitlab-org/gitlab/issues/34224
   def compare_reports(service_class, current_user = nil)
     with_reactive_cache(service_class.name, current_user&.id) do |data|
-      unless service_class.new(project, current_user)
+      unless service_class.new(project, current_user, id: id)
         .latest?(base_pipeline, actual_head_pipeline, data)
         raise InvalidateReactiveCache
       end
@@ -1335,7 +1357,7 @@ class MergeRequest < ApplicationRecord
     raise NameError, service_class unless service_class < Ci::CompareReportsBaseService
 
     current_user = User.find_by(id: current_user_id)
-    service_class.new(project, current_user).execute(base_pipeline, actual_head_pipeline)
+    service_class.new(project, current_user, id: id).execute(base_pipeline, actual_head_pipeline)
   end
 
   def all_commits

app/services/ci/generate_coverage_reports_service.rb

+# frozen_string_literal: true
+
+module Ci
+  # TODO: a couple of points with this approach:
+  # + reuses existing architecture and reactive caching
+  # - it's not a report comparison and some comparing features must be turned off.
+  # see CompareReportsBaseService for more notes.
+  # issue: https://gitlab.com/gitlab-org/gitlab/issues/34224
+  class GenerateCoverageReportsService < CompareReportsBaseService
+    def execute(base_pipeline, head_pipeline)
+      merge_request = MergeRequest.find_by_id(params[:id])
+      {
+        status: :parsed,
+        key: key(base_pipeline, head_pipeline),
+        data: head_pipeline.coverage_reports.pick(merge_request.new_paths)
+      }
+    rescue => e
+      Gitlab::ErrorTracking.track_exception(e, project_id: project.id)
+      {
+        status: :error,
+        key: key(base_pipeline, head_pipeline),
+        status_reason: _('An error occurred while fetching coverage reports.')
+      }
+    end
+
+    def latest?(base_pipeline, head_pipeline, data)
+      data&.fetch(:key, nil) == key(base_pipeline, head_pipeline)
+    end
+  end
+end

app/views/projects/merge_requests/show.html.haml

@@ -78,6 +78,7 @@
         endpoint: diffs_project_merge_request_path(@project, @merge_request, 'json', request.query_parameters),
         endpoint_metadata: diffs_metadata_project_json_merge_request_path(@project, @merge_request, 'json', request.query_parameters),
         endpoint_batch: diffs_batch_project_json_merge_request_path(@project, @merge_request, 'json', request.query_parameters),
+        endpoint_coverage: @coverage_path,
         help_page_path: suggest_changes_help_path,
         current_user_data: @current_user_data,
         project_path: project_path(@merge_request.project),

changelogs/unreleased/feat-mr-diff-coverage-visualisation.yml

+---
+title: Add Cobertura XML coverage visualization to merge request diff view
+merge_request: 21791
+author: Fabio Huser
+type: added

config/routes/merge_requests.rb

@@ -14,6 +14,7 @@ resources :merge_requests, concerns: :awardable, except: [:new, :create, :show],
     post :rebase
     get :test_reports
     get :exposed_artifacts
+    get :coverage_reports
 
     scope constraints: ->(req) { req.format == :json }, as: :json do
       get :commits

doc/ci/yaml/README.md

@@ -107,7 +107,7 @@ The following table lists available parameters for jobs:
 | [`when`](#when)                                    | When to run job. Also available: `when:manual` and `when:delayed`.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
 | [`environment`](#environment)                      | Name of an environment to which the job deploys. Also available: `environment:name`, `environment:url`, `environment:on_stop`, `environment:auto_stop_in` and `environment:action`.                                                                                                                                                                                                                                                                                                                                                                                                                                |
 | [`cache`](#cache)                                  | List of files that should be cached between subsequent runs. Also available: `cache:paths`, `cache:key`, `cache:untracked`, and `cache:policy`.                                                                                                                                                                                                                                                                                                                                                                                                                                         |
-| [`artifacts`](#artifacts)                          | List of files and directories to attach to a job on success. Also available: `artifacts:paths`, `artifacts:expose_as`, `artifacts:name`, `artifacts:untracked`, `artifacts:when`, `artifacts:expire_in`, `artifacts:reports`, and `artifacts:reports:junit`.<br><br>In GitLab [Enterprise Edition](https://about.gitlab.com/pricing/), these are available: `artifacts:reports:codequality`, `artifacts:reports:sast`, `artifacts:reports:dependency_scanning`, `artifacts:reports:container_scanning`, `artifacts:reports:dast`, `artifacts:reports:license_management`, `artifacts:reports:performance` and `artifacts:reports:metrics`. |
+| [`artifacts`](#artifacts)                          | List of files and directories to attach to a job on success. Also available: `artifacts:paths`, `artifacts:expose_as`, `artifacts:name`, `artifacts:untracked`, `artifacts:when`, `artifacts:expire_in`, `artifacts:reports`, `artifacts:reports:junit`, and `artifacts:reports:cobertura`.<br><br>In GitLab [Enterprise Edition](https://about.gitlab.com/pricing/), these are available: `artifacts:reports:codequality`, `artifacts:reports:sast`, `artifacts:reports:dependency_scanning`, `artifacts:reports:container_scanning`, `artifacts:reports:dast`, `artifacts:reports:license_management`, `artifacts:reports:performance` and `artifacts:reports:metrics`. |
 | [`dependencies`](#dependencies)                    | Restrict which artifacts are passed to a specific job by providing a list of jobs to fetch artifacts from.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | [`coverage`](#coverage)                            | Code coverage settings for a given job.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
 | [`retry`](#retry)                                  | When and how many times a job can be auto-retried in case of a failure.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
@@ -2283,6 +2283,18 @@ There are a couple of limitations on top of the [original dotenv rules](https://
 - It doesn't support empty lines and comments (`#`) in dotenv file.
 - It doesn't support quote escape, spaces in a quote, a new line expansion in a quote, in dotenv file.
 
+##### `artifacts:reports:cobertura`
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/3708) in GitLab 12.9.
+> Requires [GitLab Runner](https://docs.gitlab.com/runner/) 11.5 and above.
+
+The `cobertura` report collects [Cobertura coverage XML files](../../user/project/merge_requests/test_coverage_visualization.md).
+The collected Cobertura coverage reports will be uploaded to GitLab as an artifact
+and will be automatically shown in merge requests.
+
+Cobertura was originally developed for Java, but there are many
+third party ports for other languages like JavaScript, Python, Ruby, etc.
+
 ##### `artifacts:reports:codequality` **(STARTER)**
 
 > Introduced in GitLab 11.5. Requires GitLab Runner 11.5 and above.

doc/user/project/merge_requests/index.md

@@ -102,6 +102,7 @@ or link to useful information directly in the merge request page:
 | [Multi-Project pipelines](../../../ci/multi_project_pipelines.md) **(PREMIUM)**                        | When you set up GitLab CI/CD across multiple projects, you can visualize the entire pipeline, including all cross-project interdependencies.                                                              |
 | [Pipelines for merge requests](../../../ci/merge_request_pipelines/index.md)                           | Customize a specific pipeline structure for merge requests in order to speed the cycle up by running only important jobs.                                                                                 |
 | [Pipeline Graphs](../../../ci/pipelines/index.md#visualizing-pipelines)                                      | View the status of pipelines within the merge request, including the deployment process.                                                                                                                  |
+| [Test Coverage visualization](test_coverage_visualization.md)                                          | See test coverage results for merge requests, within the file diff.                                                                                                                                       |
 
 ### Security Reports **(ULTIMATE)**
 

doc/user/project/merge_requests/test_coverage_visualization.md

+---
+type: reference, howto
+---
+
+# Test Coverage Visualization
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/3708) in GitLab 12.9.
+
+With the help of [GitLab CI/CD](../../../ci/README.md), you can collect the test
+coverage information of your favorite testing or coverage-analysis tool, and visualize
+this information inside the file diff view of your merge requests (MRs). This will allow you
+to see which lines are covered by tests, and which lines still require coverage, before the
+MR is merged.
+
+![Test Coverage Visualization Diff View](img/test_coverage_visualization_v12_9.png)
+
+## How test coverage visualization works
+
+Collecting the coverage information is done via GitLab CI/CD's
+[artifacts reports feature](../../../ci/yaml/README.md#artifactsreports).
+You can specify one or more coverage reports to collect, including wildcard paths.
+GitLab will then take the coverage information in all the files and combine it
+together.
+
+For the coverage analysis to work, you have to provide a properly formated
+[Cobertura XML](https://cobertura.github.io/cobertura/) report to
+[`artifacts:reports:cobertura`](../../../ci/yaml/README.md#artifactsreportscobertura).
+This format was originally developed for Java, but most coverage analysis frameworks
+for other languages have plugins to add support for it, like:
+
+- [simplecov-cobertura](https://rubygems.org/gems/simplecov-cobertura) (Ruby)
+- [gocover-cobertura](https://github.com/t-yuki/gocover-cobertura) (Golang)
+
+Other coverage analysis frameworks support the format out of the box, for example:
+
+- [Istanbul](https://istanbul.js.org/docs/advanced/alternative-reporters/#cobertura) (JavaScript)
+- [Coverage.py](https://coverage.readthedocs.io/en/coverage-5.0/cmd.html#xml-reporting) (Python)
+
+Once configured, if you create a merge request that triggers a pipeline which collects
+coverage reports, the coverage will be shown in the diff view. This includes reports
+from any job in any stage in the pipeline. The coverage will be displayed for each line:
+
+- `covered` (green): lines which have been checked at least once by tests
+- `no test coverage` (orange): lines which are loaded but never executed
+- no coverage information: lines which are non-instrumented or not loaded
+
+Hovering over the coverage bar will provide further information, such as the number
+of times the line was checked by tests.
+
+## Example test coverage configuration
+
+The following [`gitlab-ci.yml`](../../../ci/yaml/README.md) example uses [Mocha](https://mochajs.org/)
+JavaScript testing and [NYC](https://github.com/istanbuljs/nyc) coverage-tooling to
+generate the coverage artifact:
+
+```yaml
+test:
+  script:
+    - npm install
+    - npx nyc --reporter cobertura mocha
+  artifacts:
+    reports:
+      cobertura: coverage/cobertura-coverage.xml
+```
+
+## Enabling the feature
+
+This feature comes with the `:coverage_report_view` feature flag disabled by
+default. This feature is disabled due to some performance issues with very large
+data sets. When [the performance issue](https://gitlab.com/gitlab-org/gitlab/issues/37725)
+is resolved, the feature will be enabled by default.
+
+To enable this feature, ask a GitLab administrator with Rails console access to
+run the following command:
+
+```ruby
+Feature.enable(:coverage_report_view)
+```

ee/app/assets/javascripts/batch_comments/components/inline_draft_comment_row.vue

@@ -16,7 +16,7 @@ export default {
 
 <template>
   <tr class="notes_holder js-temp-notes-holder">
-    <td class="notes-content" colspan="3">
+    <td class="notes-content" colspan="4">
       <div class="content"><draft-note :draft="draft" /></div>
     </td>
   </tr>

ee/app/assets/javascripts/batch_comments/components/parallel_draft_comment_row.vue

@@ -34,11 +34,11 @@ export default {
 <template>
   <tr :class="className" class="notes_holder">
     <td class="notes_line old"></td>
-    <td class="notes-content parallel old">
+    <td class="notes-content parallel old" colspan="2">
       <div v-if="leftDraft.isDraft" class="content"><draft-note :draft="leftDraft" /></div>
     </td>
     <td class="notes_line new"></td>
-    <td class="notes-content parallel new">
+    <td class="notes-content parallel new" colspan="2">
       <div v-if="rightDraft.isDraft" class="content"><draft-note :draft="rightDraft" /></div>
     </td>
   </tr>

lib/gitlab/ci/config/entry/reports.rb

@@ -14,7 +14,7 @@ module Gitlab
           ALLOWED_KEYS =
             %i[junit codequality sast dependency_scanning container_scanning
                dast performance license_management license_scanning metrics lsif
-               dotenv].freeze
+               dotenv cobertura].freeze
 
           attributes ALLOWED_KEYS
 
@@ -35,6 +35,7 @@ module Gitlab
               validates :metrics, array_of_strings_or_string: true
               validates :lsif, array_of_strings_or_string: true
               validates :dotenv, array_of_strings_or_string: true
+              validates :cobertura, array_of_strings_or_string: true
             end
           end
 

lib/gitlab/ci/parsers.rb

@@ -9,7 +9,8 @@ module Gitlab
 
       def self.parsers
         {
-          junit: ::Gitlab::Ci::Parsers::Test::Junit
+          junit: ::Gitlab::Ci::Parsers::Test::Junit,
+          cobertura: ::Gitlab::Ci::Parsers::Coverage::Cobertura
         }
       end
 

lib/gitlab/ci/parsers/coverage/cobertura.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Parsers
+      module Coverage
+        class Cobertura
+          CoberturaParserError = Class.new(Gitlab::Ci::Parsers::ParserError)
+
+          def parse!(xml_data, coverage_report)
+            root = Hash.from_xml(xml_data)
+
+            parse_all(root, coverage_report)
+          rescue Nokogiri::XML::SyntaxError
+            raise CoberturaParserError, "XML parsing failed"
+          rescue
+            raise CoberturaParserError, "Cobertura parsing failed"
+          end
+
+          private
+
+          def parse_all(root, coverage_report)
+            return unless root.present?
+
+            root.each do |key, value|
+              parse_node(key, value, coverage_report)
+            end
+          end
+
+          def parse_node(key, value, coverage_report)
+            if key == 'class'
+              Array.wrap(value).each do |item|
+                parse_class(item, coverage_report)
+              end
+            elsif value.is_a?(Hash)
+              parse_all(value, coverage_report)
+            elsif value.is_a?(Array)
+              value.each do |item|
+                parse_all(item, coverage_report)
+              end
+            end
+          end
+
+          def parse_class(file, coverage_report)
+            return unless file["filename"].present? && file["lines"].present?
+
+            parsed_lines = parse_lines(file["lines"])
+
+            coverage_report.add_file(file["filename"], Hash[parsed_lines])
+          end
+
+          def parse_lines(lines)
+            line_array = Array.wrap(lines["line"])
+
+            line_array.map do |line|
+              # Using `Integer()` here to raise exception on invalid values
+              [Integer(line["number"]), Integer(line["hits"])]
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/ci/reports/coverage_reports.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Reports
+      class CoverageReports
+        attr_reader :files
+
+        def initialize
+          @files = {}
+        end
+
+        def pick(keys)
+          coverage_files = files.select do |key|
+            keys.include?(key)
+          end
+
+          { files: coverage_files }
+        end
+
+        def add_file(name, line_coverage)
+          if files[name].present?
+            line_coverage.each { |line, hits| combine_lines(name, line, hits) }
+
+          else
+            files[name] = line_coverage
+          end
+        end
+
+        private
+
+        def combine_lines(name, line, hits)
+          if files[name][line].present?
+            files[name][line] += hits
+
+          else
+            files[name][line] = hits
+          end
+        end
+      end
+    end
+  end
+end

locale/gitlab.pot

@@ -1810,6 +1810,9 @@ msgstr ""
 msgid "An error occurred while enabling Service Desk."
 msgstr ""
 
+msgid "An error occurred while fetching coverage reports."
+msgstr ""
+
 msgid "An error occurred while fetching environments."
 msgstr ""
 
@@ -13325,6 +13328,9 @@ msgstr ""
 msgid "No template"
 msgstr ""
 
+msgid "No test coverage"
+msgstr ""
+
 msgid "No thanks, don't show this again"
 msgstr ""
 
@@ -19469,6 +19475,11 @@ msgstr ""
 msgid "Test coverage parsing"
 msgstr ""
 
+msgid "Test coverage: %d hit"
+msgid_plural "Test coverage: %d hits"
+msgstr[0] ""
+msgstr[1] ""
+
 msgid "Test failed."
 msgstr ""
 

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -984,6 +984,136 @@ describe Projects::MergeRequestsController do
     end
   end
 
+  describe 'GET coverage_reports' do
+    let(:merge_request) do
+      create(:merge_request,
+        :with_merge_request_pipeline,
+        target_project: project,
+        source_project: project)
+    end
+
+    let(:pipeline) do
+      create(:ci_pipeline,
+        :success,
+        project: merge_request.source_project,
+        ref: merge_request.source_branch,
+        sha: merge_request.diff_head_sha)
+    end
+
+    before do
+      allow_any_instance_of(MergeRequest)
+        .to receive(:find_coverage_reports)
+        .and_return(report)
+
+      allow_any_instance_of(MergeRequest)
+        .to receive(:actual_head_pipeline)
+        .and_return(pipeline)
+    end
+
+    subject do
+      get :coverage_reports, params: {
+        namespace_id: project.namespace.to_param,
+        project_id: project,
+        id: merge_request.iid
+      },
+      format: :json
+    end
+
+    describe 'permissions on a public project with private CI/CD' do
+      let(:project) { create :project, :repository, :public, :builds_private }
+      let(:report) { { status: :parsed, data: [] } }
+
+      context 'while signed out' do
+        before do
+          sign_out(user)
+        end
+
+        it 'responds with a 404' do
+          subject
+
+          expect(response).to have_gitlab_http_status(:not_found)
+          expect(response.body).to be_blank
+        end
+      end
+
+      context 'while signed in as an unrelated user' do
+        before do
+          sign_in(create(:user))
+        end
+
+        it 'responds with a 404' do
+          subject
+
+          expect(response).to have_gitlab_http_status(:not_found)
+          expect(response.body).to be_blank
+        end
+      end
+    end
+
+    context 'when pipeline has jobs with coverage reports' do
+      before do
+        allow_any_instance_of(MergeRequest)
+          .to receive(:has_coverage_reports?)
+          .and_return(true)
+      end
+
+      context 'when processing coverage reports is in progress' do
+        let(:report) { { status: :parsing } }
+
+        it 'sends polling interval' do
+          expect(Gitlab::PollingInterval).to receive(:set_header)
+
+          subject
+        end
+
+        it 'returns 204 HTTP status' do
+          subject
+
+          expect(response).to have_gitlab_http_status(:no_content)
+        end
+      end
+
+      context 'when processing coverage reports is completed' do
+        let(:report) { { status: :parsed, data: pipeline.coverage_reports } }
+
+        it 'returns coverage reports' do
+          subject
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(json_response).to eq({ 'files' => {} })
+        end
+      end
+
+      context 'when user created corrupted coverage reports' do
+        let(:report) { { status: :error, status_reason: 'Failed to parse coverage reports' } }
+
+        it 'does not send polling interval' do
+          expect(Gitlab::PollingInterval).not_to receive(:set_header)
+
+          subject
+        end
+
+        it 'returns 400 HTTP status' do
+          subject
+
+          expect(response).to have_gitlab_http_status(:bad_request)
+          expect(json_response).to eq({ 'status_reason' => 'Failed to parse coverage reports' })
+        end
+      end
+    end
+
+    context 'when pipeline does not have jobs with coverage reports' do
+      let(:report) { double }
+
+      it 'returns no content' do
+        subject
+
+        expect(response).to have_gitlab_http_status(:no_content)
+        expect(response.body).to be_empty
+      end
+    end
+  end
+
   describe 'GET test_reports' do
     let(:merge_request) do
       create(:merge_request,

spec/factories/ci/builds.rb

@@ -311,6 +311,12 @@ FactoryBot.define do
       end
     end
 
+    trait :coverage_reports do
+      after(:build) do |build|
+        build.job_artifacts << create(:ci_job_artifact, :cobertura, job: build)
+      end
+    end
+
     trait :expired do
       artifacts_expire_at { 1.minute.ago }
     end

spec/factories/ci/job_artifacts.rb

@@ -129,6 +129,36 @@ FactoryBot.define do
       end
     end
 
+    trait :cobertura do
+      file_type { :cobertura }
+      file_format { :gzip }
+
+      after(:build) do |artifact, evaluator|
+        artifact.file = fixture_file_upload(
+          Rails.root.join('spec/fixtures/cobertura/coverage.xml.gz'), 'application/x-gzip')
+      end
+    end
+
+    trait :coverage_gocov_xml do
+      file_type { :cobertura }
+      file_format { :gzip }
+
+      after(:build) do |artifact, evaluator|
+        artifact.file = fixture_file_upload(
+          Rails.root.join('spec/fixtures/cobertura/coverage_gocov_xml.xml.gz'), 'application/x-gzip')
+      end
+    end
+
+    trait :coverage_with_corrupted_data do
+      file_type { :cobertura }
+      file_format { :gzip }
+
+      after(:build) do |artifact, evaluator|
+        artifact.file = fixture_file_upload(
+          Rails.root.join('spec/fixtures/cobertura/coverage_with_corrupted_data.xml.gz'), 'application/x-gzip')
+      end
+    end
+
     trait :codequality do
       file_type { :codequality }
       file_format { :raw }

spec/factories/ci/pipelines.rb

@@ -67,6 +67,14 @@ FactoryBot.define do
         end
       end
 
+      trait :with_coverage_reports do
+        status { :success }
+
+        after(:build) do |pipeline, evaluator|
+          pipeline.builds << build(:ci_build, :coverage_reports, pipeline: pipeline, project: pipeline.project)
+        end
+      end
+
       trait :with_exposed_artifacts do
         status { :success }
 

spec/factories/merge_requests.rb

@@ -121,6 +121,18 @@ FactoryBot.define do
       end
     end
 
+    trait :with_coverage_reports do
+      after(:build) do |merge_request|
+        merge_request.head_pipeline = build(
+          :ci_pipeline,
+          :success,
+          :with_coverage_reports,
+          project: merge_request.source_project,
+          ref: merge_request.source_branch,
+          sha: merge_request.diff_head_sha)
+      end
+    end
+
     trait :with_exposed_artifacts do
       after(:build) do |merge_request|
         merge_request.head_pipeline = build(

spec/features/merge_request/user_sees_avatar_on_diff_notes_spec.rb

@@ -190,7 +190,7 @@ describe 'Merge request > User sees avatars on diff notes', :js do
 
   def find_line(line_code)
     line = find("[id='#{line_code}']")
-    line = line.find(:xpath, 'preceding-sibling::*[1][self::td]') if line.tag_name == 'td'
+    line = line.find(:xpath, 'preceding-sibling::*[1][self::td]/preceding-sibling::*[1][self::td]') if line.tag_name == 'td'
     line
   end
 end

spec/fixtures/cobertura/coverage.xml

+<?xml version='1.0'?> 
+<!DOCTYPE coverage SYSTEM "http://cobertura.sourceforge.net/xml/coverage-04.dtd">
+<!-- cobertura example file - generated by simplecov-cobertura - subset of gitlab-org/gitlab - manually modified -->
+<!-- Generated by simplecov-cobertura version 1.3.1 (https://github.com/dashingrocket/simplecov-cobertura) -->
+<coverage line-rate="0.5" branch-rate="0" lines-covered="73865" lines-valid="147397" branches-covered="0" branches-valid="0" complexity="0" version="0" timestamp="1577128350">
+  <sources>
+    <source>/tmp/projects/gitlab-ce/gitlab</source>
+  </sources>
+  <packages>
+    <package name="Controllers" line-rate="0.43" branch-rate="0" complexity="0">
+      <classes>
+        <class name="abuse_reports_controller" filename="app/controllers/abuse_reports_controller.rb" line-rate="0.3" branch-rate="0" complexity="0">
+          <methods/>
+          <lines>
+            <line number="3" branch="false" hits="1"/>
+            <line number="4" branch="false" hits="1"/>
+            <line number="6" branch="false" hits="1"/>
+            <line number="7" branch="false" hits="0"/>
+            <line number="8" branch="false" hits="0"/>
+            <line number="9" branch="false" hits="0"/>
+            <line number="12" branch="false" hits="1"/>
+            <line number="13" branch="false" hits="0"/>
+            <line number="14" branch="false" hits="0"/>
+            <line number="16" branch="false" hits="0"/>
+            <line number="17" branch="false" hits="0"/>
+            <line number="19" branch="false" hits="0"/>
+            <line number="20" branch="false" hits="0"/>
+            <line number="22" branch="false" hits="0"/>
+            <line number="26" branch="false" hits="1"/>
+            <line number="28" branch="false" hits="1"/>
+            <line number="29" branch="false" hits="0"/>
+            <line number="36" branch="false" hits="1"/>
+            <line number="37" branch="false" hits="0"/>
+            <line number="39" branch="false" hits="0"/>
+            <line number="40" branch="false" hits="0"/>
+            <line number="41" branch="false" hits="0"/>
+            <line number="42" branch="false" hits="0"/>
+          </lines>
+        </class>
+      </classes>
+    </package>
+  </packages>
+</coverage>
\ No newline at end of file

spec/fixtures/cobertura/coverage_gocov_xml.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE coverage SYSTEM "http://cobertura.sourceforge.net/xml/coverage-04.dtd">
+<!-- cobertura example file - generated by gocov-xml - subset of gitlab-org/gitaly -->
+<coverage line-rate="0.7966102" branch-rate="0" lines-covered="47" lines-valid="59" branches-covered="0" branches-valid="0" complexity="0" version="" timestamp="1577127162320">
+	<packages>
+		<package name="gitlab.com/gitlab-org/gitaly/auth" line-rate="0.7966102" branch-rate="0" complexity="0" line-count="59" line-hits="47">
+			<classes>
+				<class name="-" filename="auth/rpccredentials.go" line-rate="0.2" branch-rate="0" complexity="0" line-count="5" line-hits="1">
+					<methods>
+						<method name="RPCCredentials" signature="" line-rate="1" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="17" hits="1"></line>
+							</lines>
+						</method>
+						<method name="RPCCredentialsV2" signature="" line-rate="0" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="34" hits="0"></line>
+							</lines>
+						</method>
+						<method name="hmacToken" signature="" line-rate="0" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="52" hits="0"></line>
+								<line number="53" hits="0"></line>
+								<line number="55" hits="0"></line>
+							</lines>
+						</method>
+					</methods>
+					<lines>
+						<line number="17" hits="1"></line>
+						<line number="34" hits="0"></line>
+						<line number="52" hits="0"></line>
+						<line number="53" hits="0"></line>
+						<line number="55" hits="0"></line>
+					</lines>
+				</class>
+				<class name="rpcCredentials" filename="auth/rpccredentials.go" line-rate="0.5" branch-rate="0" complexity="0" line-count="2" line-hits="1">
+					<methods>
+						<method name="RequireTransportSecurity" signature="" line-rate="0" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="24" hits="0"></line>
+							</lines>
+						</method>
+						<method name="GetRequestMetadata" signature="" line-rate="1" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="27" hits="1"></line>
+							</lines>
+						</method>
+					</methods>
+					<lines>
+						<line number="24" hits="0"></line>
+						<line number="27" hits="1"></line>
+					</lines>
+				</class>
+				<class name="rpcCredentialsV2" filename="auth/rpccredentials.go" line-rate="0" branch-rate="0" complexity="0" line-count="3" line-hits="0">
+					<methods>
+						<method name="RequireTransportSecurity" signature="" line-rate="0" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="41" hits="0"></line>
+							</lines>
+						</method>
+						<method name="GetRequestMetadata" signature="" line-rate="0" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="44" hits="0"></line>
+							</lines>
+						</method>
+						<method name="hmacToken" signature="" line-rate="0" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="48" hits="0"></line>
+							</lines>
+						</method>
+					</methods>
+					<lines>
+						<line number="41" hits="0"></line>
+						<line number="44" hits="0"></line>
+						<line number="48" hits="0"></line>
+					</lines>
+				</class>
+				<class name="-" filename="auth/token.go" line-rate="0.9183673" branch-rate="0" complexity="0" line-count="49" line-hits="45">
+					<methods>
+						<method name="init" signature="" line-rate="1" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="38" hits="1"></line>
+							</lines>
+						</method>
+						<method name="CheckToken" signature="" line-rate="0.9285714" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="52" hits="1"></line>
+								<line number="53" hits="0"></line>
+								<line number="56" hits="1"></line>
+								<line number="57" hits="1"></line>
+								<line number="58" hits="1"></line>
+								<line number="61" hits="1"></line>
+								<line number="63" hits="1"></line>
+								<line number="64" hits="1"></line>
+								<line number="65" hits="1"></line>
+								<line number="68" hits="1"></line>
+								<line number="69" hits="1"></line>
+								<line number="72" hits="1"></line>
+								<line number="73" hits="1"></line>
+								<line number="77" hits="1"></line>
+							</lines>
+						</method>
+						<method name="tokensEqual" signature="" line-rate="1" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="81" hits="1"></line>
+							</lines>
+						</method>
+						<method name="ExtractAuthInfo" signature="" line-rate="0.90909094" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="86" hits="1"></line>
+								<line number="88" hits="1"></line>
+								<line number="89" hits="1"></line>
+								<line number="92" hits="1"></line>
+								<line number="96" hits="1"></line>
+								<line number="97" hits="1"></line>
+								<line number="100" hits="1"></line>
+								<line number="101" hits="1"></line>
+								<line number="102" hits="1"></line>
+								<line number="103" hits="0"></line>
+								<line number="106" hits="1"></line>
+							</lines>
+						</method>
+						<method name="countV2Error" signature="" line-rate="1" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="109" hits="1"></line>
+							</lines>
+						</method>
+						<method name="v2HmacInfoValid" signature="" line-rate="0.8888889" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="112" hits="1"></line>
+								<line number="113" hits="1"></line>
+								<line number="114" hits="1"></line>
+								<line number="115" hits="1"></line>
+								<line number="118" hits="1"></line>
+								<line number="119" hits="1"></line>
+								<line number="120" hits="0"></line>
+								<line number="121" hits="0"></line>
+								<line number="124" hits="1"></line>
+								<line number="125" hits="1"></line>
+								<line number="126" hits="1"></line>
+								<line number="128" hits="1"></line>
+								<line number="129" hits="1"></line>
+								<line number="130" hits="1"></line>
+								<line number="133" hits="1"></line>
+								<line number="134" hits="1"></line>
+								<line number="135" hits="1"></line>
+								<line number="138" hits="1"></line>
+							</lines>
+						</method>
+						<method name="hmacSign" signature="" line-rate="1" branch-rate="0" complexity="0" line-count="0" line-hits="0">
+							<lines>
+								<line number="142" hits="1"></line>
+								<line number="143" hits="1"></line>
+								<line number="145" hits="1"></line>
+							</lines>
+						</method>
+					</methods>
+					<lines>
+						<line number="38" hits="1"></line>
+						<line number="52" hits="1"></line>
+						<line number="53" hits="0"></line>
+						<line number="56" hits="1"></line>
+						<line number="57" hits="1"></line>
+						<line number="58" hits="1"></line>
+						<line number="61" hits="1"></line>
+						<line number="63" hits="1"></line>
+						<line number="64" hits="1"></line>
+						<line number="65" hits="1"></line>
+						<line number="68" hits="1"></line>
+						<line number="69" hits="1"></line>
+						<line number="72" hits="1"></line>
+						<line number="73" hits="1"></line>
+						<line number="77" hits="1"></line>
+						<line number="81" hits="1"></line>
+						<line number="86" hits="1"></line>
+						<line number="88" hits="1"></line>
+						<line number="89" hits="1"></line>
+						<line number="92" hits="1"></line>
+						<line number="96" hits="1"></line>
+						<line number="97" hits="1"></line>
+						<line number="100" hits="1"></line>
+						<line number="101" hits="1"></line>
+						<line number="102" hits="1"></line>
+						<line number="103" hits="0"></line>
+						<line number="106" hits="1"></line>
+						<line number="109" hits="1"></line>
+						<line number="112" hits="1"></line>
+						<line number="113" hits="1"></line>
+						<line number="114" hits="1"></line>
+						<line number="115" hits="1"></line>
+						<line number="118" hits="1"></line>
+						<line number="119" hits="1"></line>
+						<line number="120" hits="0"></line>
+						<line number="121" hits="0"></line>
+						<line number="124" hits="1"></line>
+						<line number="125" hits="1"></line>
+						<line number="126" hits="1"></line>
+						<line number="128" hits="1"></line>
+						<line number="129" hits="1"></line>
+						<line number="130" hits="1"></line>
+						<line number="133" hits="1"></line>
+						<line number="134" hits="1"></line>
+						<line number="135" hits="1"></line>
+						<line number="138" hits="1"></line>
+						<line number="142" hits="1"></line>
+						<line number="143" hits="1"></line>
+						<line number="145" hits="1"></line>
+					</lines>
+				</class>
+			</classes>
+		</package>
+	</packages>
+	<sources>
+		<source>/tmp/projects/gitlab-ce/gitaly/src/gitlab.com/gitlab-org/gitaly</source>
+	</sources>
+</coverage>

spec/fixtures/cobertura/coverage_with_corrupted_data.xml

+<?xml version="1.0" ?>
+<!DOCTYPE coverage SYSTEM "http://cobertura.sourceforge.net/xml/coverage-04.dtd">
+<!-- cobertura example file - generated by NYC - manually modified -->
+<coverage lines-valid="22" lines-covered="16" line-rate="0.7273000000000001" branches-valid="4" branches-covered="2" branch-rate="0.5" timestamp="1576756029756" complexity="0" version="0.1">
+  <sources>
+    <source>/tmp/projects/coverage-test</source>
+  </sources>
+  <packages>
+    <package name="coverage-test" line-rate="0.6842" branch-rate="0.5">
+      <classes>
+        <class name="index.js" filename="index.js" line-rate="0.6842" branch-rate="0.5">
+          <methods>
+            <method name="(anonymous_3)" hits="0" signature="()V">
+              <lines>
+                <line number="21" hits="0"/>
+              </lines>
+            </method>
+          </methods>
+          <lines>
+            <line number="21" hits="1" branch="false"/>
+            <line number="22" hits="0" branch="false"/>
+            <line number="25" hits="1" branch="true" condition-coverage="50% (1/2)"/>
+            <line number="26" hits="0" branch="false"/>
+            <line number="27" hits="0" branch="false"/>
+            <line number="28" hits="0" branch="false"/>
+            <line number="29" hits="0" branch="false"/>
+          </lines>
+        </class>
+      </classes>
+    </package>
+    <package name="coverage-test.lib.math" line-rate="1" branch-rate="1">
+      <classes>
+        <class name="add.js" filename="lib/math/add.js" line-rate="1" branch-rate="1">
+          <methods>
+            <method name="(anonymous_0)" hits="1" signature="()V">
+              <lines>
+                <line number="1" hits="1"/>
+              </lines>
+            </method>
+          </methods>
+          <lines>
+            <line null="test" hits="1" branch="false"/>
+            <line number="2" hits="1" branch="false"/>
+            <line number="3" hits="1" branch="false"/>
+          </lines>
+        </class>
+      </classes>
+    </package>
+  </packages>
+</coverage>

spec/frontend/diffs/components/app_spec.js

@@ -41,6 +41,7 @@ describe('diffs/components/app', () => {
         endpoint: TEST_ENDPOINT,
         endpointMetadata: `${TEST_HOST}/diff/endpointMetadata`,
         endpointBatch: `${TEST_HOST}/diff/endpointBatch`,
+        endpointCoverage: `${TEST_HOST}/diff/endpointCoverage`,
         projectPath: 'namespace/project',
         currentUser: {},
         changesEmptyStateIllustration: '',
@@ -95,6 +96,7 @@ describe('diffs/components/app', () => {
       jest.spyOn(wrapper.vm, 'fetchDiffFiles').mockImplementation(fetchResolver);
       jest.spyOn(wrapper.vm, 'fetchDiffFilesMeta').mockImplementation(fetchResolver);
       jest.spyOn(wrapper.vm, 'fetchDiffFilesBatch').mockImplementation(fetchResolver);
+      jest.spyOn(wrapper.vm, 'fetchCoverageFiles').mockImplementation(fetchResolver);
       jest.spyOn(wrapper.vm, 'setDiscussions').mockImplementation(() => {});
       jest.spyOn(wrapper.vm, 'startRenderDiffsQueue').mockImplementation(() => {});
       jest.spyOn(wrapper.vm, 'unwatchDiscussions').mockImplementation(() => {});
@@ -250,6 +252,7 @@ describe('diffs/components/app', () => {
         expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesMeta).not.toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
+        expect(wrapper.vm.fetchCoverageFiles).toHaveBeenCalled();
         expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
         expect(wrapper.vm.diffFilesLength).toEqual(100);
         expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
@@ -269,6 +272,7 @@ describe('diffs/components/app', () => {
         expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
+        expect(wrapper.vm.fetchCoverageFiles).toHaveBeenCalled();
         expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
         expect(wrapper.vm.diffFilesLength).toEqual(100);
         expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
@@ -286,6 +290,7 @@ describe('diffs/components/app', () => {
         expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
+        expect(wrapper.vm.fetchCoverageFiles).toHaveBeenCalled();
         expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
         expect(wrapper.vm.diffFilesLength).toEqual(100);
         expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();

spec/javascripts/diffs/components/inline_diff_table_row_spec.js

@@ -12,6 +12,7 @@ describe('InlineDiffTableRow', () => {
     vm = createComponentWithStore(Vue.extend(InlineDiffTableRow), createStore(), {
       line: thisLine,
       fileHash: diffFileMockData.file_hash,
+      filePath: diffFileMockData.file_path,
       contextLinesPath: 'contextLinesPath',
       isHighlighted: false,
     }).$mount();
@@ -39,4 +40,64 @@ describe('InlineDiffTableRow', () => {
       .then(done)
       .catch(done.fail);
   });
+
+  describe('sets coverage title and class', () => {
+    it('for lines with coverage', done => {
+      vm.$nextTick()
+        .then(() => {
+          const name = diffFileMockData.file_path;
+          const line = thisLine.new_line;
+
+          vm.$store.state.diffs.coverageFiles = { files: { [name]: { [line]: 5 } } };
+
+          return vm.$nextTick();
+        })
+        .then(() => {
+          const coverage = vm.$el.querySelector('.line-coverage');
+
+          expect(coverage.title).toContain('Test coverage: 5 hits');
+          expect(coverage.classList).toContain('coverage');
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+
+    it('for lines without coverage', done => {
+      vm.$nextTick()
+        .then(() => {
+          const name = diffFileMockData.file_path;
+          const line = thisLine.new_line;
+
+          vm.$store.state.diffs.coverageFiles = { files: { [name]: { [line]: 0 } } };
+
+          return vm.$nextTick();
+        })
+        .then(() => {
+          const coverage = vm.$el.querySelector('.line-coverage');
+
+          expect(coverage.title).toContain('No test coverage');
+          expect(coverage.classList).toContain('no-coverage');
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+
+    it('for unknown lines', done => {
+      vm.$nextTick()
+        .then(() => {
+          vm.$store.state.diffs.coverageFiles = {};
+
+          return vm.$nextTick();
+        })
+        .then(() => {
+          const coverage = vm.$el.querySelector('.line-coverage');
+
+          expect(coverage.title).not.toContain('Coverage');
+          expect(coverage.classList).not.toContain('coverage');
+          expect(coverage.classList).not.toContain('no-coverage');
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+  });
 });

spec/javascripts/diffs/components/parallel_diff_table_row_spec.js

@@ -14,6 +14,7 @@ describe('ParallelDiffTableRow', () => {
       vm = createComponentWithStore(Vue.extend(ParallelDiffTableRow), createStore(), {
         line: thisLine,
         fileHash: diffFileMockData.file_hash,
+        filePath: diffFileMockData.file_path,
         contextLinesPath: 'contextLinesPath',
         isHighlighted: false,
       }).$mount();
@@ -52,6 +53,7 @@ describe('ParallelDiffTableRow', () => {
       vm = createComponentWithStore(Vue.extend(ParallelDiffTableRow), createStore(), {
         line: thisLine,
         fileHash: diffFileMockData.file_hash,
+        filePath: diffFileMockData.file_path,
         contextLinesPath: 'contextLinesPath',
         isHighlighted: false,
       }).$mount();
@@ -81,5 +83,65 @@ describe('ParallelDiffTableRow', () => {
         .then(done)
         .catch(done.fail);
     });
+
+    describe('sets coverage title and class', () => {
+      it('for lines with coverage', done => {
+        vm.$nextTick()
+          .then(() => {
+            const name = diffFileMockData.file_path;
+            const line = rightLine.new_line;
+
+            vm.$store.state.diffs.coverageFiles = { files: { [name]: { [line]: 5 } } };
+
+            return vm.$nextTick();
+          })
+          .then(() => {
+            const coverage = vm.$el.querySelector('.line-coverage.right-side');
+
+            expect(coverage.title).toContain('Test coverage: 5 hits');
+            expect(coverage.classList).toContain('coverage');
+          })
+          .then(done)
+          .catch(done.fail);
+      });
+
+      it('for lines without coverage', done => {
+        vm.$nextTick()
+          .then(() => {
+            const name = diffFileMockData.file_path;
+            const line = rightLine.new_line;
+
+            vm.$store.state.diffs.coverageFiles = { files: { [name]: { [line]: 0 } } };
+
+            return vm.$nextTick();
+          })
+          .then(() => {
+            const coverage = vm.$el.querySelector('.line-coverage.right-side');
+
+            expect(coverage.title).toContain('No test coverage');
+            expect(coverage.classList).toContain('no-coverage');
+          })
+          .then(done)
+          .catch(done.fail);
+      });
+
+      it('for unknown lines', done => {
+        vm.$nextTick()
+          .then(() => {
+            vm.$store.state.diffs.coverageFiles = {};
+
+            return vm.$nextTick();
+          })
+          .then(() => {
+            const coverage = vm.$el.querySelector('.line-coverage.right-side');
+
+            expect(coverage.title).not.toContain('Coverage');
+            expect(coverage.classList).not.toContain('coverage');
+            expect(coverage.classList).not.toContain('no-coverage');
+          })
+          .then(done)
+          .catch(done.fail);
+      });
+    });
   });
 });

spec/javascripts/diffs/store/actions_spec.js

@@ -12,6 +12,7 @@ import actions, {
   fetchDiffFiles,
   fetchDiffFilesBatch,
   fetchDiffFilesMeta,
+  fetchCoverageFiles,
   assignDiscussionsToDiff,
   removeDiscussionsFromDiff,
   startRenderDiffsQueue,
@@ -73,6 +74,7 @@ describe('DiffsStoreActions', () => {
       const endpoint = '/diffs/set/endpoint';
       const endpointMetadata = '/diffs/set/endpoint/metadata';
       const endpointBatch = '/diffs/set/endpoint/batch';
+      const endpointCoverage = '/diffs/set/coverage_reports';
       const projectPath = '/root/project';
       const dismissEndpoint = '/-/user_callouts';
       const showSuggestPopover = false;
@@ -84,6 +86,7 @@ describe('DiffsStoreActions', () => {
           endpoint,
           endpointBatch,
           endpointMetadata,
+          endpointCoverage,
           projectPath,
           dismissEndpoint,
           showSuggestPopover,
@@ -93,6 +96,7 @@ describe('DiffsStoreActions', () => {
           endpoint: '',
           endpointBatch: '',
           endpointMetadata: '',
+          endpointCoverage: '',
           projectPath: '',
           dismissEndpoint: '',
           showSuggestPopover: true,
@@ -105,6 +109,7 @@ describe('DiffsStoreActions', () => {
               endpoint,
               endpointMetadata,
               endpointBatch,
+              endpointCoverage,
               projectPath,
               dismissEndpoint,
               showSuggestPopover,
@@ -318,6 +323,44 @@ describe('DiffsStoreActions', () => {
     });
   });
 
+  describe('fetchCoverageFiles', () => {
+    let mock;
+    const endpointCoverage = '/fetch';
+
+    beforeEach(() => {
+      mock = new MockAdapter(axios);
+    });
+
+    afterEach(() => mock.restore());
+
+    it('should commit SET_COVERAGE_DATA with received response', done => {
+      const data = { files: { 'app.js': { '1': 0, '2': 1 } } };
+
+      mock.onGet(endpointCoverage).reply(200, { data });
+
+      testAction(
+        fetchCoverageFiles,
+        {},
+        { endpointCoverage },
+        [{ type: types.SET_COVERAGE_DATA, payload: { data } }],
+        [],
+        done,
+      );
+    });
+
+    it('should show flash on API error', done => {
+      const flashSpy = spyOnDependency(actions, 'createFlash');
+
+      mock.onGet(endpointCoverage).reply(400);
+
+      testAction(fetchCoverageFiles, {}, { endpointCoverage }, [], [], () => {
+        expect(flashSpy).toHaveBeenCalledTimes(1);
+        expect(flashSpy).toHaveBeenCalledWith(jasmine.stringMatching('Something went wrong'));
+        done();
+      });
+    });
+  });
+
   describe('setHighlightedRow', () => {
     it('should mark currently selected diff and set lineHash and fileHash of highlightedRow', () => {
       testAction(setHighlightedRow, 'ABC_123', {}, [

spec/javascripts/diffs/store/getters_spec.js

@@ -282,4 +282,34 @@ describe('Diffs Module Getters', () => {
       expect(getters.currentDiffIndex(localState)).toEqual(0);
     });
   });
+
+  describe('fileLineCoverage', () => {
+    beforeEach(() => {
+      Object.assign(localState.coverageFiles, { files: { 'app.js': { '1': 0, '2': 5 } } });
+    });
+
+    it('returns empty object when no coverage data is available', () => {
+      Object.assign(localState.coverageFiles, {});
+
+      expect(getters.fileLineCoverage(localState)('test.js', 2)).toEqual({});
+    });
+
+    it('returns empty object when unknown filename is passed', () => {
+      expect(getters.fileLineCoverage(localState)('test.js', 2)).toEqual({});
+    });
+
+    it('returns no-coverage info when correct filename and line is passed', () => {
+      expect(getters.fileLineCoverage(localState)('app.js', 1)).toEqual({
+        text: 'No test coverage',
+        class: 'no-coverage',
+      });
+    });
+
+    it('returns coverage info when correct filename and line is passed', () => {
+      expect(getters.fileLineCoverage(localState)('app.js', 2)).toEqual({
+        text: 'Test coverage: 5 hits',
+        class: 'coverage',
+      });
+    });
+  });
 });

spec/javascripts/diffs/store/mutations_spec.js

@@ -123,6 +123,17 @@ describe('DiffsStoreMutations', () => {
     });
   });
 
+  describe('SET_COVERAGE_DATA', () => {
+    it('should set coverage data properly', () => {
+      const state = { coverageFiles: {} };
+      const coverage = { 'app.js': { '1': 0, '2': 1 } };
+
+      mutations[types.SET_COVERAGE_DATA](state, coverage);
+
+      expect(state.coverageFiles).toEqual(coverage);
+    });
+  });
+
   describe('SET_DIFF_VIEW_TYPE', () => {
     it('should set diff view type properly', () => {
       const state = {};

spec/lib/gitlab/ci/config/entry/reports_spec.rb

@@ -45,6 +45,7 @@ describe Gitlab::Ci::Config::Entry::Reports do
         :performance | 'performance.json'
         :lsif | 'lsif.json'
         :dotenv | 'build.dotenv'
+        :cobertura | 'cobertura-coverage.xml'
       end
 
       with_them do

spec/lib/gitlab/ci/parsers/coverage/cobertura_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+describe Gitlab::Ci::Parsers::Coverage::Cobertura do
+  describe '#parse!' do
+    subject { described_class.new.parse!(cobertura, coverage_report) }
+
+    let(:coverage_report) { Gitlab::Ci::Reports::CoverageReports.new }
+
+    context 'when data is Cobertura style XML' do
+      context 'when there is no <class>' do
+        let(:cobertura) { '' }
+
+        it 'parses XML and returns empty coverage' do
+          expect { subject }.not_to raise_error
+
+          expect(coverage_report.files).to eq({})
+        end
+      end
+
+      context 'when there is a single <class>' do
+        context 'with no lines' do
+          let(:cobertura) do
+            <<-EOF.strip_heredoc
+            <classes><class filename="app.rb"></class></classes>
+            EOF
+          end
+
+          it 'parses XML and returns empty coverage' do
+            expect { subject }.not_to raise_error
+
+            expect(coverage_report.files).to eq({})
+          end
+        end
+
+        context 'with a single line' do
+          let(:cobertura) do
+            <<-EOF.strip_heredoc
+            <classes>
+              <class filename="app.rb"><lines>
+                <line number="1" hits="2"/>
+              </lines></class>
+            </classes>
+            EOF
+          end
+
+          it 'parses XML and returns a single file with coverage' do
+            expect { subject }.not_to raise_error
+
+            expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2 } })
+          end
+        end
+
+        context 'with multipe lines and methods info' do
+          let(:cobertura) do
+            <<-EOF.strip_heredoc
+            <classes>
+              <class filename="app.rb"><methods/><lines>
+                <line number="1" hits="2"/>
+                <line number="2" hits="0"/>
+              </lines></class>
+            </classes>
+            EOF
+          end
+
+          it 'parses XML and returns a single file with coverage' do
+            expect { subject }.not_to raise_error
+
+            expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2, 2 => 0 } })
+          end
+        end
+      end
+
+      context 'when there are multipe <class>' do
+        context 'with the same filename and different lines' do
+          let(:cobertura) do
+            <<-EOF.strip_heredoc
+            <classes>
+              <class filename="app.rb"><methods/><lines>
+                <line number="1" hits="2"/>
+                <line number="2" hits="0"/>
+              </lines></class>
+              <class filename="app.rb"><methods/><lines>
+                <line number="6" hits="1"/>
+                <line number="7" hits="1"/>
+              </lines></class>
+            </classes>
+            EOF
+          end
+
+          it 'parses XML and returns a single file with merged coverage' do
+            expect { subject }.not_to raise_error
+
+            expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2, 2 => 0, 6 => 1, 7 => 1 } })
+          end
+        end
+
+        context 'with the same filename and lines' do
+          let(:cobertura) do
+            <<-EOF.strip_heredoc
+            <packages><package><classes>
+              <class filename="app.rb"><methods/><lines>
+                <line number="1" hits="2"/>
+                <line number="2" hits="0"/>
+              </lines></class>
+              <class filename="app.rb"><methods/><lines>
+                <line number="1" hits="1"/>
+                <line number="2" hits="1"/>
+              </lines></class>
+            </classes></package></packages>
+            EOF
+          end
+
+          it 'parses XML and returns a single file with summed-up coverage' do
+            expect { subject }.not_to raise_error
+
+            expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 3, 2 => 1 } })
+          end
+        end
+
+        context 'with missing filename' do
+          let(:cobertura) do
+            <<-EOF.strip_heredoc
+            <classes>
+              <class filename="app.rb"><methods/><lines>
+                <line number="1" hits="2"/>
+                <line number="2" hits="0"/>
+              </lines></class>
+              <class><methods/><lines>
+                <line number="6" hits="1"/>
+                <line number="7" hits="1"/>
+              </lines></class>
+            </classes>
+            EOF
+          end
+
+          it 'parses XML and ignores class with missing name' do
+            expect { subject }.not_to raise_error
+
+            expect(coverage_report.files).to eq({ 'app.rb' => { 1 => 2, 2 => 0 } })
+          end
+        end
+
+        context 'with invalid line information' do
+          let(:cobertura) do
+            <<-EOF.strip_heredoc
+            <classes>
+              <class filename="app.rb"><methods/><lines>
+                <line number="1" hits="2"/>
+                <line number="2" hits="0"/>
+              </lines></class>
+              <class filename="app.rb"><methods/><lines>
+                <line null="test" hits="1"/>
+                <line number="7" hits="1"/>
+              </lines></class>
+            </classes>
+            EOF
+          end
+
+          it 'raises an error' do
+            expect { subject }.to raise_error(described_class::CoberturaParserError)
+          end
+        end
+      end
+    end
+
+    context 'when data is not Cobertura style XML' do
+      let(:cobertura) { { coverage: '12%' }.to_json }
+
+      it 'raises an error' do
+        expect { subject }.to raise_error(described_class::CoberturaParserError)
+      end
+    end
+  end
+end

spec/lib/gitlab/ci/parsers_spec.rb

@@ -6,7 +6,7 @@ describe Gitlab::Ci::Parsers do
   describe '.fabricate!' do
     subject { described_class.fabricate!(file_type) }
 
-    context 'when file_type exists' do
+    context 'when file_type is junit' do
       let(:file_type) { 'junit' }
 
       it 'fabricates the class' do
@@ -14,6 +14,14 @@ describe Gitlab::Ci::Parsers do
       end
     end
 
+    context 'when file_type is cobertura' do
+      let(:file_type) { 'cobertura' }
+
+      it 'fabricates the class' do
+        is_expected.to be_a(described_class::Coverage::Cobertura)
+      end
+    end
+
     context 'when file_type does not exist' do
       let(:file_type) { 'undefined' }
 

spec/lib/gitlab/ci/reports/coverage_reports_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Ci::Reports::CoverageReports do
+  let(:coverage_report) { described_class.new }
+
+  it { expect(coverage_report.files).to eq({}) }
+
+  describe '#pick' do
+    before do
+      coverage_report.add_file('app.rb', { 1 => 0, 2 => 1 })
+      coverage_report.add_file('routes.rb', { 3 => 1, 4 => 0 })
+    end
+
+    it 'returns only picked files while ignoring nonexistent ones' do
+      expect(coverage_report.pick(['routes.rb', 'nonexistent.txt'])).to eq({
+        files: { 'routes.rb' => { 3 => 1, 4 => 0 } }
+      })
+    end
+  end
+
+  describe '#add_file' do
+    context 'when providing two individual files' do
+      before do
+        coverage_report.add_file('app.rb', { 1 => 0, 2 => 1 })
+        coverage_report.add_file('routes.rb', { 3 => 1, 4 => 0 })
+      end
+
+      it 'initializes a new test suite and returns it' do
+        expect(coverage_report.files).to eq({
+          'app.rb' => { 1 => 0, 2 => 1 },
+          'routes.rb' => { 3 => 1, 4 => 0 }
+        })
+      end
+    end
+
+    context 'when providing the same files twice' do
+      context 'with different line coverage' do
+        before do
+          coverage_report.add_file('admin.rb', { 1 => 0, 2 => 1 })
+          coverage_report.add_file('admin.rb', { 3 => 1, 4 => 0 })
+        end
+
+        it 'initializes a new test suite and returns it' do
+          expect(coverage_report.files).to eq({
+            'admin.rb' => { 1 => 0, 2 => 1, 3 => 1, 4 => 0 }
+          })
+        end
+      end
+
+      context 'with identical line coverage' do
+        before do
+          coverage_report.add_file('projects.rb', { 1 => 0, 2 => 1 })
+          coverage_report.add_file('projects.rb', { 1 => 0, 2 => 1 })
+        end
+
+        it 'initializes a new test suite and returns it' do
+          expect(coverage_report.files).to eq({
+            'projects.rb' => { 1 => 0, 2 => 2 }
+          })
+        end
+      end
+    end
+  end
+end

spec/models/ci/build_spec.rb

@@ -3946,6 +3946,53 @@ describe Ci::Build do
     end
   end
 
+  describe '#collect_coverage_reports!' do
+    subject { build.collect_coverage_reports!(coverage_report) }
+
+    let(:coverage_report) { Gitlab::Ci::Reports::CoverageReports.new }
+
+    it { expect(coverage_report.files).to eq({}) }
+
+    context 'when build has a coverage report' do
+      context 'when there is a Cobertura coverage report from simplecov-cobertura' do
+        before do
+          create(:ci_job_artifact, :cobertura, job: build, project: build.project)
+        end
+
+        it 'parses blobs and add the results to the coverage report' do
+          expect { subject }.not_to raise_error
+
+          expect(coverage_report.files.keys).to match_array(['app/controllers/abuse_reports_controller.rb'])
+          expect(coverage_report.files['app/controllers/abuse_reports_controller.rb'].count).to eq(23)
+        end
+      end
+
+      context 'when there is a Cobertura coverage report from gocov-xml' do
+        before do
+          create(:ci_job_artifact, :coverage_gocov_xml, job: build, project: build.project)
+        end
+
+        it 'parses blobs and add the results to the coverage report' do
+          expect { subject }.not_to raise_error
+
+          expect(coverage_report.files.keys).to match_array(['auth/token.go', 'auth/rpccredentials.go'])
+          expect(coverage_report.files['auth/token.go'].count).to eq(49)
+          expect(coverage_report.files['auth/rpccredentials.go'].count).to eq(10)
+        end
+      end
+
+      context 'when there is a corrupted Cobertura coverage report' do
+        before do
+          create(:ci_job_artifact, :coverage_with_corrupted_data, job: build, project: build.project)
+        end
+
+        it 'raises an error' do
+          expect { subject }.to raise_error(Gitlab::Ci::Parsers::Coverage::Cobertura::CoberturaParserError)
+        end
+      end
+    end
+  end
+
   describe '#report_artifacts' do
     subject { build.report_artifacts }
 

spec/models/ci/job_artifact_spec.rb

@@ -70,6 +70,22 @@ describe Ci::JobArtifact do
     end
   end
 
+  describe '.coverage_reports' do
+    subject { described_class.coverage_reports }
+
+    context 'when there is a coverage report' do
+      let!(:artifact) { create(:ci_job_artifact, :cobertura) }
+
+      it { is_expected.to eq([artifact]) }
+    end
+
+    context 'when there are no coverage reports' do
+      let!(:artifact) { create(:ci_job_artifact, :archive) }
+
+      it { is_expected.to be_empty }
+    end
+  end
+
   describe '.erasable' do
     subject { described_class.erasable }
 

spec/models/ci/pipeline_spec.rb

@@ -344,9 +344,9 @@ describe Ci::Pipeline, :mailer do
   end
 
   describe '.with_reports' do
-    subject { described_class.with_reports(Ci::JobArtifact.test_reports) }
-
     context 'when pipeline has a test report' do
+      subject { described_class.with_reports(Ci::JobArtifact.test_reports) }
+
       let!(:pipeline_with_report) { create(:ci_pipeline, :with_test_reports) }
 
       it 'selects the pipeline' do
@@ -354,7 +354,19 @@ describe Ci::Pipeline, :mailer do
       end
     end
 
+    context 'when pipeline has a coverage report' do
+      subject { described_class.with_reports(Ci::JobArtifact.coverage_reports) }
+
+      let!(:pipeline_with_report) { create(:ci_pipeline, :with_coverage_reports) }
+
+      it 'selects the pipeline' do
+        is_expected.to eq([pipeline_with_report])
+      end
+    end
+
     context 'when pipeline does not have metrics reports' do
+      subject { described_class.with_reports(Ci::JobArtifact.test_reports) }
+
       let!(:pipeline_without_report) { create(:ci_empty_pipeline) }
 
       it 'does not select the pipeline' do
@@ -2730,6 +2742,43 @@ describe Ci::Pipeline, :mailer do
     end
   end
 
+  describe '#coverage_reports' do
+    subject { pipeline.coverage_reports }
+
+    context 'when pipeline has multiple builds with coverage reports' do
+      let!(:build_rspec) { create(:ci_build, :success, name: 'rspec', pipeline: pipeline, project: project) }
+      let!(:build_golang) { create(:ci_build, :success, name: 'golang', pipeline: pipeline, project: project) }
+
+      before do
+        create(:ci_job_artifact, :cobertura, job: build_rspec, project: project)
+        create(:ci_job_artifact, :coverage_gocov_xml, job: build_golang, project: project)
+      end
+
+      it 'returns coverage reports with collected data' do
+        expect(subject.files.keys).to match_array([
+          "auth/token.go",
+          "auth/rpccredentials.go",
+          "app/controllers/abuse_reports_controller.rb"
+        ])
+      end
+
+      context 'when builds are retried' do
+        let!(:build_rspec) { create(:ci_build, :retried, :success, name: 'rspec', pipeline: pipeline, project: project) }
+        let!(:build_golang) { create(:ci_build, :retried, :success, name: 'golang', pipeline: pipeline, project: project) }
+
+        it 'does not take retried builds into account' do
+          expect(subject.files).to eql({})
+        end
+      end
+    end
+
+    context 'when pipeline does not have any builds with coverage reports' do
+      it 'returns empty coverage reports' do
+        expect(subject.files).to eql({})
+      end
+    end
+  end
+
   describe '#total_size' do
     let!(:build_job1) { create(:ci_build, pipeline: pipeline, stage_idx: 0) }
     let!(:build_job2) { create(:ci_build, pipeline: pipeline, stage_idx: 0) }

spec/models/merge_request_spec.rb

@@ -908,6 +908,16 @@ describe MergeRequest do
     end
   end
 
+  describe '#new_paths' do
+    let(:merge_request) do
+      create(:merge_request, source_branch: 'expand-collapse-files', target_branch: 'master')
+    end
+
+    it 'returns new path of changed files' do
+      expect(merge_request.new_paths.count).to eq(105)
+    end
+  end
+
   describe "#related_notes" do
     let!(:merge_request) { create(:merge_request) }
 
@@ -1581,6 +1591,24 @@ describe MergeRequest do
     end
   end
 
+  describe '#has_coverage_reports?' do
+    subject { merge_request.has_coverage_reports? }
+
+    let(:project) { create(:project, :repository) }
+
+    context 'when head pipeline has coverage reports' do
+      let(:merge_request) { create(:merge_request, :with_coverage_reports, source_project: project) }
+
+      it { is_expected.to be_truthy }
+    end
+
+    context 'when head pipeline does not have coverage reports' do
+      let(:merge_request) { create(:merge_request, source_project: project) }
+
+      it { is_expected.to be_falsey }
+    end
+  end
+
   describe '#calculate_reactive_cache' do
     let(:project) { create(:project, :repository) }
     let(:merge_request) { create(:merge_request, source_project: project) }
@@ -1663,6 +1691,60 @@ describe MergeRequest do
     end
   end
 
+  describe '#find_coverage_reports' do
+    let(:project) { create(:project, :repository) }
+    let(:merge_request) { create(:merge_request, :with_coverage_reports, source_project: project) }
+    let(:pipeline) { merge_request.head_pipeline }
+
+    subject { merge_request.find_coverage_reports }
+
+    context 'when head pipeline has coverage reports' do
+      let!(:job) do
+        create(:ci_build, options: { artifacts: { reports: { cobertura: ['cobertura-coverage.xml'] } } }, pipeline: pipeline)
+      end
+
+      let!(:artifacts_metadata) { create(:ci_job_artifact, :metadata, job: job) }
+
+      context 'when reactive cache worker is parsing results asynchronously' do
+        it 'returns status' do
+          expect(subject[:status]).to eq(:parsing)
+        end
+      end
+
+      context 'when reactive cache worker is inline' do
+        before do
+          synchronous_reactive_cache(merge_request)
+        end
+
+        it 'returns status and data' do
+          expect(subject[:status]).to eq(:parsed)
+        end
+
+        context 'when an error occurrs' do
+          before do
+            merge_request.update!(head_pipeline: nil)
+          end
+
+          it 'returns an error message' do
+            expect(subject[:status]).to eq(:error)
+          end
+        end
+
+        context 'when cached results is not latest' do
+          before do
+            allow_next_instance_of(Ci::GenerateCoverageReportsService) do |service|
+              allow(service).to receive(:latest?).and_return(false)
+            end
+          end
+
+          it 'raises and InvalidateReactiveCache error' do
+            expect { subject }.to raise_error(ReactiveCaching::InvalidateReactiveCache)
+          end
+        end
+      end
+    end
+  end
+
   describe '#compare_test_reports' do
     subject { merge_request.compare_test_reports }
 

spec/services/ci/retry_build_service_spec.rb

@@ -36,7 +36,8 @@ describe Ci::RetryBuildService do
        job_artifacts_performance job_artifacts_lsif
        job_artifacts_codequality job_artifacts_metrics scheduled_at
        job_variables waiting_for_resource_at job_artifacts_metrics_referee
-       job_artifacts_network_referee job_artifacts_dotenv needs].freeze
+       job_artifacts_network_referee job_artifacts_dotenv
+       job_artifacts_cobertura needs].freeze
 
   IGNORE_ACCESSORS =
     %i[type lock_version target_url base_tags trace_sections