assert.throws fails in component integration tests with ember 2.12

[sergproua]

I installed Ember 2.12 and created new project with a component and a test to ensure it throws an error if required attribute is not provided. I can't get this test to pass.

npm install -g ember-cli@2.12
ember new ember-test
cd ember-test
ember g component dummy-component
...copy/paste code below...
ember test

dummy-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  value: Ember.computed(() => {
    Ember.assert("Someone forgot to provide a required value attribute");
  })
});

dummy-component.hbs

{{value}}
{{yield}}

dummy-component-test.js

import { moduleForComponent, test } from 'ember-qunit';
import hbs from 'htmlbars-inline-precompile';

moduleForComponent('dummy-component', 'Integration | Component | dummy component', {
  integration: true
});

test('it throws', function(assert) {
  assert.throws(() => {
    this.render(hbs`{{dummy-component}}`);
  }, 'Error: Assertion Failed: Someone forgot to provide a required value attribute');
});

Error:

not ok 7 PhantomJS 2.1 - Integration | Component | dummy component: it throws
    ---
        actual: >
            false
        expected: >
            true
        stack: >
            exception@http://localhost:7357/assets/test-support.js:7664:49
            adapterDispatch@http://localhost:7357/assets/vendor.js:50288:22
            dispatchError@http://localhost:7357/assets/vendor.js:28557:23
            invokeWithOnError@http://localhost:7357/assets/vendor.js:10921:14
            flush@http://localhost:7357/assets/vendor.js:10977:15
            flush@http://localhost:7357/assets/vendor.js:11101:20
            end@http://localhost:7357/assets/vendor.js:11171:28
            run@http://localhost:7357/assets/vendor.js:11285:19
            run@http://localhost:7357/assets/vendor.js:33262:32
            render@http://localhost:7357/assets/test-support.js:8538:30
            http://localhost:7357/assets/tests.js:129:19
            throws@http://localhost:7357/assets/test-support.js:4609:17
            http://localhost:7357/assets/tests.js:128:18
            runTest@http://localhost:7357/assets/test-support.js:3696:34
            run@http://localhost:7357/assets/test-support.js:3682:13
            http://localhost:7357/assets/test-support.js:3860:15
            process@http://localhost:7357/assets/test-support.js:5094:26
            begin@http://localhost:7357/assets/test-support.js:5077:11
            http://localhost:7357/assets/test-support.js:4294:11
        message: >
            Error: Assertion Failed: Someone forgot to provide a required value attribute
        Log: |
            { type: 'error', text: 'null\n' }
    ...

Also asked here
http://stackoverflow.com/questions/42978212/ember-qunit-assert-throws-does-not-work

[sergproua]

workarounds/solutions by @workmanw:

1. use addon ember-qunit-assert-helpers
2. this little helper

test('it throws', function (assert) {
  expectEmberAssert(assert, () => {
    this.render(hbs`{{dummy-component}}`);
  }, 'Someone forgot to provide a required value attribute');
});

[wmadden]

You can also solve this problem by using this.subject() instead of this.render():

import { moduleForComponent, test } from 'ember-qunit';
import hbs from 'htmlbars-inline-precompile';

moduleForComponent('dummy-component', 'Unit | Component | dummy component', {
  unit: true,
});

test('it throws', function(assert) {
  assert.throws(() => {
    this.subject({ /* attributes */ });
  }, 'Error: Assertion Failed: Someone forgot to provide a required value attribute');
});

This has the advantage that it doesn't require an extra library, and uses a unit test instead of an integration test.

[Turbo87]

It looks like https://github.com/workmanw/ember-qunit-assert-helpers is the best solution for now.

[erichaus]

is there any way to do this w/o extra libraries using the newer test style?

[rwjblue]

@erichonkanen

https://discuss.emberjs.com/t/how-to-catch-errors-in-component-rendering-test/14854
emberjs/ember-test-helpers#310

[lvegerano]

This happens in utils test. I cant test for error throwing.

test('it throws if params are empty', function(assert) {
    const missingFirst = () => {
      throw new Error('foo');
    };
    assert.throws(missingFirst(), 'param 1 missing');
  });