Merge branch 'winh-promise-rejects-fail-tests' into 'master'

Make JavaScript tests fail for unhandled Promise rejections

Closes #33845 and #33623

See merge request !12264

8 files changed, 257 insertions, 160 deletions

diff --git a/app/assets/javascripts/boards/components/board_new_issue.js b/app/assets/javascripts/boards/components/board_new_issue.js
index b1c47b09c35..4af8b0c7713 100644
--- a/app/assets/javascripts/boards/components/board_new_issue.js
+++ b/app/assets/javascripts/boards/components/board_new_issue.js
@@ -17,7 +17,7 @@ export default {
   methods: {
     submit(e) {
       e.preventDefault();
-      if (this.title.trim() === '') return;
+      if (this.title.trim() === '') return Promise.resolve();
 
       this.error = false;
 
@@ -29,7 +29,10 @@ export default {
         assignees: [],
       });
 
-      this.list.newIssue(issue)
+      eventHub.$emit(`scroll-board-list-${this.list.id}`);
+      this.cancel();
+
+      return this.list.newIssue(issue)
         .then(() => {
           // Need this because our jQuery very kindly disables buttons on ALL form submissions
           $(this.$refs.submitButton).enable();
@@ -47,9 +50,6 @@ export default {
           // Show error message
           this.error = true;
         });
-
-      eventHub.$emit(`scroll-board-list-${this.list.id}`);
-      this.cancel();
     },
     cancel() {
       this.title = '';
diff --git a/app/assets/javascripts/boards/models/list.js b/app/assets/javascripts/boards/models/list.js
index 548de1a4c52..b4b09b3876e 100644
--- a/app/assets/javascripts/boards/models/list.js
+++ b/app/assets/javascripts/boards/models/list.js
@@ -112,8 +112,7 @@ class List {
       .then((resp) => {
         const data = resp.json();
         issue.id = data.iid;
-      })
-      .then(() => {
+
         if (this.issuesSize > 1) {
           const moveBeforeIid = this.issues[1].id;
           gl.boardService.moveIssue(issue.id, null, null, null, moveBeforeIid);
diff --git a/app/assets/javascripts/filtered_search/filtered_search_manager.js b/app/assets/javascripts/filtered_search/filtered_search_manager.js
index c7c8d42e677..1425769d2de 100644
--- a/app/assets/javascripts/filtered_search/filtered_search_manager.js
+++ b/app/assets/javascripts/filtered_search/filtered_search_manager.js
@@ -40,6 +40,10 @@ class FilteredSearchManager {
         return [];
       })
       .then((searches) => {
+        if (!searches) {
+          return;
+        }
+
         // Put any searches that may have come in before
         // we fetched the saved searches ahead of the already saved ones
         const resultantSearches = this.recentSearchesStore.setRecentSearches(
diff --git a/spec/javascripts/boards/board_new_issue_spec.js b/spec/javascripts/boards/board_new_issue_spec.js
index 832877de71c..c0a7323a505 100644
--- a/spec/javascripts/boards/board_new_issue_spec.js
+++ b/spec/javascripts/boards/board_new_issue_spec.js
@@ -12,6 +12,7 @@ import './mock_data';
 describe('Issue boards new issue form', () => {
   let vm;
   let list;
+  let newIssueMock;
   const promiseReturn = {
     json() {
       return {
@@ -21,7 +22,11 @@ describe('Issue boards new issue form', () => {
   };
 
   const submitIssue = () => {
-    vm.$el.querySelector('.btn-success').click();
+    const dummySubmitEvent = {
+      preventDefault() {},
+    };
+    vm.$refs.submitButton = vm.$el.querySelector('.btn-success');
+    return vm.submit(dummySubmitEvent);
   };
 
   beforeEach((done) => {
@@ -32,29 +37,35 @@ describe('Issue boards new issue form', () => {
     gl.issueBoards.BoardsStore.create();
     gl.IssueBoardsApp = new Vue();
 
-    setTimeout(() => {
-      list = new List(listObj);
-
-      spyOn(gl.boardService, 'newIssue').and.callFake(() => new Promise((resolve, reject) => {
-        if (vm.title === 'error') {
-          reject();
-        } else {
-          resolve(promiseReturn);
-        }
-      }));
-
-      vm = new BoardNewIssueComp({
-        propsData: {
-          list,
-        },
-      }).$mount();
-
-      done();
-    }, 0);
+    list = new List(listObj);
+
+    newIssueMock = Promise.resolve(promiseReturn);
+    spyOn(list, 'newIssue').and.callFake(() => newIssueMock);
+
+    vm = new BoardNewIssueComp({
+      propsData: {
+        list,
+      },
+    }).$mount();
+
+    Vue.nextTick()
+      .then(done)
+      .catch(done.fail);
   });
 
-  afterEach(() => {
-    Vue.http.interceptors = _.without(Vue.http.interceptors, boardsMockInterceptor);
+  it('calls submit if submit button is clicked', (done) => {
+    spyOn(vm, 'submit');
+    vm.title = 'Testing Title';
+
+    Vue.nextTick()
+      .then(() => {
+        vm.$el.querySelector('.btn-success').click();
+
+        expect(vm.submit.calls.count()).toBe(1);
+        expect(vm.$refs['submit-button']).toBe(vm.$el.querySelector('.btn-success'));
+      })
+      .then(done)
+      .catch(done.fail);
   });
 
   it('disables submit button if title is empty', () => {
@@ -64,136 +75,122 @@ describe('Issue boards new issue form', () => {
   it('enables submit button if title is not empty', (done) => {
     vm.title = 'Testing Title';
 
-    setTimeout(() => {
-      expect(vm.$el.querySelector('.form-control').value).toBe('Testing Title');
-      expect(vm.$el.querySelector('.btn-success').disabled).not.toBe(true);
-
-      done();
-    }, 0);
+    Vue.nextTick()
+      .then(() => {
+        expect(vm.$el.querySelector('.form-control').value).toBe('Testing Title');
+        expect(vm.$el.querySelector('.btn-success').disabled).not.toBe(true);
+      })
+      .then(done)
+      .catch(done.fail);
   });
 
   it('clears title after clicking cancel', (done) => {
     vm.$el.querySelector('.btn-default').click();
 
-    setTimeout(() => {
-      expect(vm.title).toBe('');
-      done();
-    }, 0);
+    Vue.nextTick()
+      .then(() => {
+        expect(vm.title).toBe('');
+      })
+      .then(done)
+      .catch(done.fail);
   });
 
   it('does not create new issue if title is empty', (done) => {
-    submitIssue();
-
-    setTimeout(() => {
-      expect(gl.boardService.newIssue).not.toHaveBeenCalled();
-      done();
-    }, 0);
+    submitIssue()
+      .then(() => {
+        expect(list.newIssue).not.toHaveBeenCalled();
+      })
+      .then(done)
+      .catch(done.fail);
   });
 
   describe('submit success', () => {
     it('creates new issue', (done) => {
       vm.title = 'submit title';
 
-      setTimeout(() => {
-        submitIssue();
-
-        expect(gl.boardService.newIssue).toHaveBeenCalled();
-        done();
-      }, 0);
+      Vue.nextTick()
+        .then(submitIssue)
+        .then(() => {
+          expect(list.newIssue).toHaveBeenCalled();
+        })
+        .then(done)
+        .catch(done.fail);
     });
 
     it('enables button after submit', (done) => {
       vm.title = 'submit issue';
 
-      setTimeout(() => {
-        submitIssue();
-
-        expect(vm.$el.querySelector('.btn-success').disabled).toBe(false);
-        done();
-      }, 0);
+      Vue.nextTick()
+        .then(submitIssue)
+        .then(() => {
+          expect(vm.$el.querySelector('.btn-success').disabled).toBe(false);
+        })
+        .then(done)
+        .catch(done.fail);
     });
 
     it('clears title after submit', (done) => {
       vm.title = 'submit issue';
 
-      Vue.nextTick(() => {
-        submitIssue();
-
-        setTimeout(() => {
+      Vue.nextTick()
+        .then(submitIssue)
+        .then(() => {
           expect(vm.title).toBe('');
-          done();
-        }, 0);
-      });
-    });
-
-    it('adds new issue to top of list after submit request', (done) => {
-      vm.title = 'submit issue';
-
-      setTimeout(() => {
-        submitIssue();
-
-        setTimeout(() => {
-          expect(list.issues.length).toBe(2);
-          expect(list.issues[0].title).toBe('submit issue');
-          expect(list.issues[0].subscribed).toBe(true);
-          done();
-        }, 0);
-      }, 0);
+        })
+        .then(done)
+        .catch(done.fail);
     });
 
     it('sets detail issue after submit', (done) => {
       expect(gl.issueBoards.BoardsStore.detail.issue.title).toBe(undefined);
       vm.title = 'submit issue';
 
-      setTimeout(() => {
-        submitIssue();
-
-        setTimeout(() => {
+      Vue.nextTick()
+        .then(submitIssue)
+        .then(() => {
           expect(gl.issueBoards.BoardsStore.detail.issue.title).toBe('submit issue');
-          done();
-        }, 0);
-      }, 0);
+        })
+        .then(done)
+        .catch(done.fail);
     });
 
     it('sets detail list after submit', (done) => {
       vm.title = 'submit issue';
 
-      setTimeout(() => {
-        submitIssue();
-
-        setTimeout(() => {
+      Vue.nextTick()
+        .then(submitIssue)
+        .then(() => {
           expect(gl.issueBoards.BoardsStore.detail.list.id).toBe(list.id);
-          done();
-        }, 0);
-      }, 0);
+        })
+        .then(done)
+        .catch(done.fail);
     });
   });
 
   describe('submit error', () => {
-    it('removes issue', (done) => {
+    beforeEach(() => {
+      newIssueMock = Promise.reject(new Error('My hovercraft is full of eels!'));
       vm.title = 'error';
+    });
 
-      setTimeout(() => {
-        submitIssue();
-
-        setTimeout(() => {
+    it('removes issue', (done) => {
+      Vue.nextTick()
+        .then(submitIssue)
+        .then(() => {
           expect(list.issues.length).toBe(1);
-          done();
-        }, 0);
-      }, 0);
+        })
+        .then(done)
+        .catch(done.fail);
     });
 
     it('shows error', (done) => {
-      vm.title = 'error';
-
-      setTimeout(() => {
-        submitIssue();
-
-        setTimeout(() => {
+      Vue.nextTick()
+        .then(submitIssue)
+        .then(() => {
           expect(vm.error).toBe(true);
-          done();
-        }, 0);
-      }, 0);
+        })
+        .then(done)
+        .catch(done.fail);
     });
   });
 });
diff --git a/spec/javascripts/boards/list_spec.js b/spec/javascripts/boards/list_spec.js
index 8e3d9fd77a0..db50829a276 100644
--- a/spec/javascripts/boards/list_spec.js
+++ b/spec/javascripts/boards/list_spec.js
@@ -150,4 +150,41 @@ describe('List model', () => {
       expect(list.getIssues).toHaveBeenCalled();
     });
   });
+
+  describe('newIssue', () => {
+    beforeEach(() => {
+      spyOn(gl.boardService, 'newIssue').and.returnValue(Promise.resolve({
+        json() {
+          return {
+            iid: 42,
+          };
+        },
+      }));
+    });
+
+    it('adds new issue to top of list', (done) => {
+      list.issues.push(new ListIssue({
+        title: 'Testing',
+        iid: _.random(10000),
+        confidential: false,
+        labels: [list.label],
+        assignees: [],
+      }));
+      const dummyIssue = new ListIssue({
+        title: 'new issue',
+        iid: _.random(10000),
+        confidential: false,
+        labels: [list.label],
+        assignees: [],
+      });
+
+      list.newIssue(dummyIssue)
+        .then(() => {
+          expect(list.issues.length).toBe(2);
+          expect(list.issues[0]).toBe(dummyIssue);
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+  });
 });
diff --git a/spec/javascripts/filtered_search/filtered_search_manager_spec.js b/spec/javascripts/filtered_search/filtered_search_manager_spec.js
index 8d239c9cc3f..16ae649ee60 100644
--- a/spec/javascripts/filtered_search/filtered_search_manager_spec.js
+++ b/spec/javascripts/filtered_search/filtered_search_manager_spec.js
@@ -48,18 +48,23 @@ describe('Filtered Search Manager', () => {
       </div>
     `);
 
+    spyOn(gl.FilteredSearchDropdownManager.prototype, 'setDropdown').and.callFake(() => {});
+  });
+
+  const initializeManager = () => {
+    /* eslint-disable jasmine/no-unsafe-spy */
     spyOn(gl.FilteredSearchManager.prototype, 'loadSearchParamsFromURL').and.callFake(() => {});
     spyOn(gl.FilteredSearchManager.prototype, 'tokenChange').and.callFake(() => {});
-    spyOn(gl.FilteredSearchDropdownManager.prototype, 'setDropdown').and.callFake(() => {});
     spyOn(gl.FilteredSearchDropdownManager.prototype, 'updateDropdownOffset').and.callFake(() => {});
     spyOn(gl.utils, 'getParameterByName').and.returnValue(null);
     spyOn(gl.FilteredSearchVisualTokens, 'unselectTokens').and.callThrough();
+    /* eslint-enable jasmine/no-unsafe-spy */
 
     input = document.querySelector('.filtered-search');
     tokensContainer = document.querySelector('.tokens-container');
     manager = new gl.FilteredSearchManager();
     manager.setup();
-  });
+  };
 
   afterEach(() => {
     manager.cleanup();
@@ -67,33 +72,34 @@ describe('Filtered Search Manager', () => {
 
   describe('class constructor', () => {
     const isLocalStorageAvailable = 'isLocalStorageAvailable';
-    let filteredSearchManager;
 
     beforeEach(() => {
       spyOn(RecentSearchesService, 'isAvailable').and.returnValue(isLocalStorageAvailable);
       spyOn(recentSearchesStoreSrc, 'default');
       spyOn(RecentSearchesRoot.prototype, 'render');
-
-      filteredSearchManager = new gl.FilteredSearchManager();
-      filteredSearchManager.setup();
-
-      return filteredSearchManager;
     });
 
     it('should instantiate RecentSearchesStore with isLocalStorageAvailable', () => {
+      manager = new gl.FilteredSearchManager();
+
       expect(RecentSearchesService.isAvailable).toHaveBeenCalled();
       expect(recentSearchesStoreSrc.default).toHaveBeenCalledWith({
         isLocalStorageAvailable,
         allowedKeys: gl.FilteredSearchTokenKeys.getKeys(),
       });
     });
+  });
+
+  describe('setup', () => {
+    beforeEach(() => {
+      manager = new gl.FilteredSearchManager();
+    });
 
     it('should not instantiate Flash if an RecentSearchesServiceError is caught', () => {
       spyOn(RecentSearchesService.prototype, 'fetch').and.callFake(() => Promise.reject(new RecentSearchesServiceError()));
       spyOn(window, 'Flash');
 
-      filteredSearchManager = new gl.FilteredSearchManager();
-      filteredSearchManager.setup();
+      manager.setup();
 
       expect(window.Flash).not.toHaveBeenCalled();
     });
@@ -102,6 +108,7 @@ describe('Filtered Search Manager', () => {
   describe('searchState', () => {
     beforeEach(() => {
       spyOn(gl.FilteredSearchManager.prototype, 'search').and.callFake(() => {});
+      initializeManager();
     });
 
     it('should blur button', () => {
@@ -148,6 +155,10 @@ describe('Filtered Search Manager', () => {
   describe('search', () => {
     const defaultParams = '?scope=all&utf8=%E2%9C%93&state=opened';
 
+    beforeEach(() => {
+      initializeManager();
+    });
+
     it('should search with a single word', (done) => {
       input.value = 'searchTerm';
 
@@ -197,6 +208,10 @@ describe('Filtered Search Manager', () => {
   });
 
   describe('handleInputPlaceholder', () => {
+    beforeEach(() => {
+      initializeManager();
+    });
+
     it('should render placeholder when there is no input', () => {
       expect(input.placeholder).toEqual(placeholder);
     });
@@ -223,6 +238,10 @@ describe('Filtered Search Manager', () => {
   });
 
   describe('checkForBackspace', () => {
+    beforeEach(() => {
+      initializeManager();
+    });
+
     describe('tokens and no input', () => {
       beforeEach(() => {
         tokensContainer.innerHTML = FilteredSearchSpecHelper.createTokensContainerHTML(
@@ -260,6 +279,10 @@ describe('Filtered Search Manager', () => {
   });
 
   describe('removeToken', () => {
+    beforeEach(() => {
+      initializeManager();
+    });
+
     it('removes token even when it is already selected', () => {
       tokensContainer.innerHTML = FilteredSearchSpecHelper.createTokensContainerHTML(
         FilteredSearchSpecHelper.createFilterVisualTokenHTML('milestone', 'none', true),
@@ -291,6 +314,7 @@ describe('Filtered Search Manager', () => {
 
   describe('removeSelectedTokenKeydown', () => {
     beforeEach(() => {
+      initializeManager();
       tokensContainer.innerHTML = FilteredSearchSpecHelper.createTokensContainerHTML(
         FilteredSearchSpecHelper.createFilterVisualTokenHTML('milestone', 'none', true),
       );
@@ -344,27 +368,39 @@ describe('Filtered Search Manager', () => {
       spyOn(gl.FilteredSearchVisualTokens, 'removeSelectedToken').and.callThrough();
       spyOn(gl.FilteredSearchManager.prototype, 'handleInputPlaceholder').and.callThrough();
       spyOn(gl.FilteredSearchManager.prototype, 'toggleClearSearchButton').and.callThrough();
-      manager.removeSelectedToken();
+      initializeManager();
     });
 
     it('calls FilteredSearchVisualTokens.removeSelectedToken', () => {
+      manager.removeSelectedToken();
+
       expect(gl.FilteredSearchVisualTokens.removeSelectedToken).toHaveBeenCalled();
     });
 
     it('calls handleInputPlaceholder', () => {
+      manager.removeSelectedToken();
+
       expect(manager.handleInputPlaceholder).toHaveBeenCalled();
     });
 
     it('calls toggleClearSearchButton', () => {
+      manager.removeSelectedToken();
+
       expect(manager.toggleClearSearchButton).toHaveBeenCalled();
     });
 
     it('calls update dropdown offset', () => {
+      manager.removeSelectedToken();
+
       expect(manager.dropdownManager.updateDropdownOffset).toHaveBeenCalled();
     });
   });
 
   describe('toggleInputContainerFocus', () => {
+    beforeEach(() => {
+      initializeManager();
+    });
+
     it('toggles on focus', () => {
       input.focus();
       expect(document.querySelector('.filtered-search-box').classList.contains('focus')).toEqual(true);
diff --git a/spec/javascripts/issue_show/components/app_spec.js b/spec/javascripts/issue_show/components/app_spec.js
index 276e01fc82f..9df92318864 100644
--- a/spec/javascripts/issue_show/components/app_spec.js
+++ b/spec/javascripts/issue_show/components/app_spec.js
@@ -3,17 +3,9 @@ import '~/render_math';
 import '~/render_gfm';
 import issuableApp from '~/issue_show/components/app.vue';
 import eventHub from '~/issue_show/event_hub';
+import Poll from '~/lib/utils/poll';
 import issueShowData from '../mock_data';
 
-const issueShowInterceptor = data => (request, next) => {
-  next(request.respondWith(JSON.stringify(data), {
-    status: 200,
-    headers: {
-      'POLL-INTERVAL': 1,
-    },
-  }));
-};
-
 function formatText(text) {
   return text.trim().replace(/\s\s+/g, ' ');
 }
@@ -24,10 +16,10 @@ describe('Issuable output', () => {
   let vm;
 
   beforeEach(() => {
-    const IssuableDescriptionComponent = Vue.extend(issuableApp);
-    Vue.http.interceptors.push(issueShowInterceptor(issueShowData.initialRequest));
-
     spyOn(eventHub, '$emit');
+    spyOn(Poll.prototype, 'makeRequest');
+
+    const IssuableDescriptionComponent = Vue.extend(issuableApp);
 
     vm = new IssuableDescriptionComponent({
       propsData: {
@@ -54,9 +46,18 @@ describe('Issuable output', () => {
   });
 
   it('should render a title/description/edited and update title/description/edited on update', (done) => {
-    setTimeout(() => {
-      const editedText = vm.$el.querySelector('.edited-text');
+    vm.poll.options.successCallback({
+      json() {
+        return issueShowData.initialRequest;
+      },
+    });
 
+    let editedText;
+    Vue.nextTick()
+    .then(() => {
+      editedText = vm.$el.querySelector('.edited-text');
+    })
+    .then(() => {
       expect(document.querySelector('title').innerText).toContain('this is a title (#1)');
       expect(vm.$el.querySelector('.title').innerHTML).toContain('<p>this is a title</p>');
       expect(vm.$el.querySelector('.wiki').innerHTML).toContain('<p>this is a description!</p>');
@@ -64,22 +65,27 @@ describe('Issuable output', () => {
       expect(formatText(editedText.innerText)).toMatch(/Edited[\s\S]+?by Some User/);
       expect(editedText.querySelector('.author_link').href).toMatch(/\/some_user$/);
       expect(editedText.querySelector('time')).toBeTruthy();
-
-      Vue.http.interceptors.push(issueShowInterceptor(issueShowData.secondRequest));
-
-      setTimeout(() => {
-        expect(document.querySelector('title').innerText).toContain('2 (#1)');
-        expect(vm.$el.querySelector('.title').innerHTML).toContain('<p>2</p>');
-        expect(vm.$el.querySelector('.wiki').innerHTML).toContain('<p>42</p>');
-        expect(vm.$el.querySelector('.js-task-list-field').value).toContain('42');
-        expect(vm.$el.querySelector('.edited-text')).toBeTruthy();
-        expect(formatText(vm.$el.querySelector('.edited-text').innerText)).toMatch(/Edited[\s\S]+?by Other User/);
-        expect(editedText.querySelector('.author_link').href).toMatch(/\/other_user$/);
-        expect(editedText.querySelector('time')).toBeTruthy();
-
-        done();
+    })
+    .then(() => {
+      vm.poll.options.successCallback({
+        json() {
+          return issueShowData.secondRequest;
+        },
       });
-    });
+    })
+    .then(Vue.nextTick)
+    .then(() => {
+      expect(document.querySelector('title').innerText).toContain('2 (#1)');
+      expect(vm.$el.querySelector('.title').innerHTML).toContain('<p>2</p>');
+      expect(vm.$el.querySelector('.wiki').innerHTML).toContain('<p>42</p>');
+      expect(vm.$el.querySelector('.js-task-list-field').value).toContain('42');
+      expect(vm.$el.querySelector('.edited-text')).toBeTruthy();
+      expect(formatText(vm.$el.querySelector('.edited-text').innerText)).toMatch(/Edited[\s\S]+?by Other User/);
+      expect(editedText.querySelector('.author_link').href).toMatch(/\/other_user$/);
+      expect(editedText.querySelector('time')).toBeTruthy();
+    })
+    .then(done)
+    .catch(done.fail);
   });
 
   it('shows actions if permissions are correct', (done) => {
@@ -344,21 +350,23 @@ describe('Issuable output', () => {
 
   describe('open form', () => {
     it('shows locked warning if form is open & data is different', (done) => {
-      Vue.http.interceptors.push(issueShowInterceptor(issueShowData.initialRequest));
+      vm.poll.options.successCallback({
+        json() {
+          return issueShowData.initialRequest;
+        },
+      });
 
       Vue.nextTick()
-        .then(() => new Promise((resolve) => {
-          setTimeout(resolve);
-        }))
         .then(() => {
           vm.openForm();
 
-          Vue.http.interceptors.push(issueShowInterceptor(issueShowData.secondRequest));
-
-          return new Promise((resolve) => {
-            setTimeout(resolve);
+          vm.poll.options.successCallback({
+            json() {
+              return issueShowData.secondRequest;
+            },
           });
         })
+        .then(Vue.nextTick)
         .then(() => {
           expect(
             vm.formState.lockedWarningVisible,
@@ -367,9 +375,8 @@ describe('Issuable output', () => {
           expect(
             vm.$el.querySelector('.alert'),
           ).not.toBeNull();
-
-          done();
         })
+        .then(done)
         .catch(done.fail);
     });
   });
diff --git a/spec/javascripts/test_bundle.js b/spec/javascripts/test_bundle.js
index f0d51bd0902..075b72f35b2 100644
--- a/spec/javascripts/test_bundle.js
+++ b/spec/javascripts/test_bundle.js
@@ -22,6 +22,19 @@ window.gl = window.gl || {};
 window.gl.TEST_HOST = 'http://test.host';
 window.gon = window.gon || {};
 
+let hasUnhandledPromiseRejections = false;
+
+window.addEventListener('unhandledrejection', (event) => {
+  hasUnhandledPromiseRejections = true;
+  console.error('Unhandled promise rejection:');
+  console.error(event.reason.stack || event.reason);
+});
+
+const checkUnhandledPromiseRejections = (done) => {
+  expect(hasUnhandledPromiseRejections).toBe(false);
+  done();
+};
+
 // HACK: Chrome 59 disconnects if there are too many synchronous tests in a row
 // because it appears to lock up the thread that communicates to Karma's socket
 // This async beforeEach gets called on every spec and releases the JS thread long
@@ -63,6 +76,10 @@ testsContext.keys().forEach(function (path) {
   }
 });
 
+it('has no unhandled Promise rejections', (done) => {
+  setTimeout(checkUnhandledPromiseRejections(done), 1000);
+});
+
 // if we're generating coverage reports, make sure to include all files so
 // that we can catch files with 0% coverage
 // see: https://github.com/deepsweet/istanbul-instrumenter-loader/issues/15