Feature - adds setupOnerror function to allow patching Ember.onerror in tests

addon-test-support/@ember/test-helpers/index.ts

@@ -7,6 +7,7 @@ export {
   unsetContext,
   pauseTest,
   resumeTest,
+  setupOnerror,
 } from './setup-context';
 export { default as teardownContext } from './teardown-context';
 export { default as setupRenderingContext, render, clearRender } from './setup-rendering-context';

addon-test-support/@ember/test-helpers/setup-context.ts

@@ -132,6 +132,29 @@ export function resumeTest(): void {
   context.resumeTest();
 }
 
+const ORIGINAL_EMBER_ONERROR: (error: Error) => void | undefined = Ember.onerror;
+
+/**
+  Sets the Ember.onerror function for the duration of a single test. This
+  value is reset after each test to ensure correct test isolation.
+
+  @public
+  @param {Function} onError the onError function to be set on Ember.onerror
+*/
+export function setupOnerror(onError: (error: Error) => void): void {
+  let context = getContext();
+  let contextGuid = guidFor(context);
+  let contextCleanup = CLEANUP[contextGuid];
+
+  if (!Array.isArray(contextCleanup)) {
+    throw new Error(
+      'You must use `setupContext` / `setupRenderingContext` / `setupApplicationContext` in order to use `setupOnerror`'
+    );
+  }
+
+  Ember.onerror = onError;
+}
+
 export const CLEANUP = Object.create(null);
 
 /**
@@ -261,6 +284,10 @@ export default function(
         }, 'TestAdapter paused promise');
       };
 
+      CLEANUP[contextGuid].push(() => {
+        Ember.onerror = ORIGINAL_EMBER_ONERROR;
+      });
+
       _setupAJAXHooks();
 
       return context as TestContext;

tests/unit/setup-ember-onerror-test.js

@@ -0,0 +1,60 @@
+import Ember from 'ember';
+import { module, test } from 'qunit';
+import hasEmberVersion from '@ember/test-helpers/has-ember-version';
+import { setupContext, teardownContext, setupOnerror } from '@ember/test-helpers';
+
+module('setupOnerror', function() {
+  if (!hasEmberVersion(2, 4)) {
+    test('Will throw if on < Ember 2.4', function(assert) {
+      assert.expect(1);
+
+      assert.throws(function() {
+        setupOnerror();
+      }, 'The `setupOnerror` function requires that you be on a minimum version of Ember 2.4.');
+    });
+  }
+
+  if (hasEmberVersion(2, 4)) {
+    test('Ember.onerror is undefined by default', function(assert) {
+      assert.expect(1);
+
+      assert.equal(Ember.onerror, undefined);
+    });
+
+    test('Ember.onerror is set correctly when using setupOnerror', async function(assert) {
+      assert.expect(2);
+
+      let context = {};
+      let onerror = err => err;
+
+      assert.equal(Ember.onerror, undefined);
+
+      await setupContext(context);
+
+      setupOnerror(onerror);
+
+      assert.equal(Ember.onerror, onerror);
+
+      await teardownContext(context);
+    });
+
+    test('Ember.onerror is reset correctly when teardownContext is invoked', async function(assert) {
+      assert.expect(3);
+
+      let context = {};
+      let onerror = err => err;
+
+      assert.equal(Ember.onerror, undefined);
+
+      await setupContext(context);
+
+      setupOnerror(onerror);
+
+      assert.equal(Ember.onerror, onerror);
+
+      await teardownContext(context);
+
+      assert.equal(Ember.onerror, undefined);
+    });
+  }
+});