Why does an expectation in $nextTick never fail? - vue.js

I need to use $nextTick in order to test some parts of my program. Somehow, it breaks my tests and make them success all the time - even when they should fail.
A minimal test sample would look like this:
import App from "./App";
import { shallowMount } from "#vue/test-utils";
it("should fail", () => {
const wrapper = shallowMount(App);
wrapper.vm.$nextTick(() => {
expect(1).toBe(3);
done();
});
});
You can find a sandbox example here
If you open the console, you should find the following error messages:
[Vue warn]: Error in nextTick: "Error: expect(received).toBe(expected)
Error: expect(received).toBe(expected)
Why does the test success? Why are the errors ignored? How do I use $nextTick properly if note like so?

In order to wait until Vue.js has finished updating the DOM after a
data change, you can use Vue.nextTick(callback) immediately after the
data is changed. The callback will be called after the DOM has been
updated.
I can not see any trigger that change DOM in your test. And you missed done argument in test callback
For example in the following this is wrapper.find('button').trigger('click')
it('fetches async when a button is clicked', (done) => {
const wrapper = shallowMount(Foo)
wrapper.find('button').trigger('click')
wrapper.vm.$nextTick(() => {
expect(wrapper.vm.value).toBe('value')
done()
})
})

Related

Rethrowing an error causes vue warning in jest test

I've got a vue application which exists of a page component and a nested child component, which makes a async post-request. If the request is failing, an error is thrown, which is propagated to the top component (Page.vue). This top component handles all errors of its child with the errorCaptured-Lifecycle hook. Here is an working example on stackblitz
The mechanism is working fine and no warning is displayed for my app. However, I want to test my child component isolated with jest and vue-test-utils. Therefore, I made a test:
import { mount } from "#vue/test-utils";
import Child from "./Child";
jest.mock("./api", () => ({
createSomething: jest.fn(),
}));
it("creation is erroneous", async () => {
const wrapper = mount(Child);
createSomething.mockImplementation(() => {
throw new Error("error");
});
let createAction = wrapper.find("[data-test-create]");
await createAction.trigger("click");
});
However, because the error is rethrown and never catched by the parent component, there is always a console log statement in my test output:
console.warn
[Vue warn]: Unhandled error during execution of native event handler
at <Child ref="VTU_COMPONENT" >
at <VTUROOT>
How can i solve this? I tried to wrap await createAction.trigger("click"); with try/catch but its not working. Do I need to mock the errorCaptured lifecycle of my parent?
One solution is to set a no-op app.config.errorHandler via the global.config mounting option:
const wrapper = mount(Child, {
global: {
config: {
errorHandler(err) { /* ignore */ },
},
},
})
demo

Mock window.location.reload with sinon

I'm writting tests with sinon for a section of Vue code that performs a reload with window.location.reload();.
The code works correctly, but the test is failing with an error Error: Not implemented: navigation (except hash changes)
If I delete that line of code, the tests don't crash.
How can I write a sinon test that runs correctly through that line of code?
I'm not sure if I need to stub that line, although I'm not sure how could I do it for a property.
Any ideas?
Consider onbeforeunload which throws an error and prevents an actual page reloading, and assert.throws catching the error. Something like this:
describe("#location.reload", () => {
it("works well", () => {
window.onbeforeunload = () => {
throw new Error();
};
assert.throws(location.reload);
});
});

Aurelia-testing: Failed to execute 'replaceChild' on 'Node': parameter 1 is not of type 'Node'

I am using for the first time the aurelia-testing package to test my HTML code.
I seem to have followed the docs to set up my test as follows:
describe('Contextual Menu HTML View test suite', function () {
let component: ComponentTester;
beforeEach(function () {
component = StageComponent
.withResources('../../src/components/modal/contextual-menu')
.inView('<contextual-menu is-active.two-way="activateMenu"></contextual-menu>')
.boundTo({ activateMenu: false });
});
it('should not add the is-active class to the root element', async function () {
await component.create(bootstrap);
const rootElement = await waitForDocumentElement('.qa-contextual-menu');
expect(rootElement.classList.contains('is-active')).toBe(false);
});
afterEach(function () {
component.dispose();
});
});
I tried using just bind instead of two-way but that fails too.
I tried both with a document.querySelector and with waitForDocumentElement, both cases fail, but anyways I assume the error comes from earlier.
I am getting an error and I am not sure why. Could you put on the tracks to identify the root cause of the following:
TypeError: Failed to execute 'replaceChild' on 'Node': parameter 1 is not of type 'Node'.
at Object.convert (/Users/lemoustachiste/work/lm-frontend/node_modules/jest-environment-jsdom/node_modules/jsdom/lib/jsdom/living/generated/Node.js:573:11)
at HTMLDivElement.replaceChild (/Users/lemoustachiste/work/lm-frontend/node_modules/jest-environment-jsdom/node_modules/jsdom/lib/jsdom/living/generated/Node.js:292:31)
at NodeJsDom.replaceNode (/Users/lemoustachiste/work/lm-frontend/node_modules/aurelia-pal-nodejs/dist/nodejs-dom.js:95:29)
at makeElementIntoAnchor (/Users/lemoustachiste/work/lm-frontend/node_modules/aurelia-templating/dist/commonjs/aurelia-templating.js:2432:19)
at applyInstructions (/Users/lemoustachiste/work/lm-frontend/node_modules/aurelia-templating/dist/commonjs/aurelia-templating.js:2479:17)
at ViewFactory.create (/Users/lemoustachiste/work/lm-frontend/node_modules/aurelia-templating/dist/commonjs/aurelia-templating.js:2707:7)
at TemplatingEngine.enhance (/Users/lemoustachiste/work/lm-frontend/node_modules/aurelia-templating/dist/commonjs/aurelia-templating.js:5290:24)
at /Users/lemoustachiste/work/lm-frontend/node_modules/aurelia-framework/dist/commonjs/aurelia-framework.js:176:28
at new Promise (<anonymous>)
at Aurelia.enhance (/Users/lemoustachiste/work/lm-frontend/node_modules/aurelia-framework/dist/commonjs/aurelia-framework.js:174:12)
Thanks a lot
I am not a jest user. So I simply used the scaffolded TS jest skeleton app from aurelia-cli (au new jest-skeleton --unattended --select typescript,jest,vscode). And found that to be working.
It seems the you are missing the following configuration in your jest.config.js.
testEnvironment: "node",
After only adding that, the tests started working.

How to disable the "Global error handler detected" warning in vue test utils

I'm creating async tests using vue-test-utils and jest using the approach described here:
https://vue-test-utils.vuejs.org/guides/#what-about-nexttick
where you set Vue.config.errorHandler = done like shown below
test('Then we are shown events in EventCreate component', done => {
Vue.config.errorHandler = done
This is working and when an error is thrown in a promise handler in a component my tests will fail. However I'm getting this warning.
console.error node_modules/#vue/test-utils/dist/vue-test-utils.js:1421
[vue-test-utils]: Global error handler detected (Vue.config.errorHandler).
Vue Test Utils sets a custom error handler to throw errors thrown by instances. If you want this behavior in your tests, you must remove the global error handler.
I don't want to spam my test output with this warning. Is there a way to disable it?
This is how I did
beforeEach(() => {
jest.spyOn(console, 'error');
console.error.mockImplementation(() => 'some error');
});
afterEach(() => {
console.error.mockRestore();
});

Jest unresolved promise do not fail

Jest docs says:
Unresolved Promises
If a promise doesn't resolve at all, this error might be thrown:
(and so on)
In my case this not happen.
I have this test:
test('detect infinite loop', () => {
expect.assertions(1);
const vastPromise = VastUtils.parseFromUrl(infiniteLoopUrl);
const expectedError =
new VastError(VastErrorCodes.WRAPPER_LIMIT_REACHED);
return expect(vastPromise).rejects.toEqual(expectedError);
});
VastUtils simply fetch an XML located at infiniteLoopUrl, parse it, and if this xml point to another xml, VastUtils follow the link, parse the new xml, merge them and repeat the process.
Now, infiniteLoopUrl point to an XML that refers itself, so it is an infinite loop.
"correctly", the code follow xml link infinitely, and never resolve or reject the promise.
I expect above test fail after a certain timeout, but it didn't.
Someone can help me?
Thanks
EDIT:
I'm trying to reproduce an infinite Promise loop with a smaller example, and this is what i've noticed:
this test correctly FAIL after 5s:
test('Promise2', () => {
const genPromise = (): Promise<void> => {
return new Promise((res) => {
setTimeout(() => {
res();
}, 200);
})
.then(() => {
return genPromise();
});
};
const vastPromise = genPromise();
const expectedError =
new VastError(VastErrorCodes.WRAPPER_LIMIT_REACHED);
return expect(vastPromise).rejects.toEqual(expectedError);
});
This test DO NOT FAIL after 5s (jest remain in an infinite loop)
test('Promise', () => {
const genPromise = (prom: Promise<void>): Promise<void> => {
return prom
.then(() => {
return genPromise(Promise.resolve());
});
};
const vastPromise = genPromise(Promise.resolve());
const expectedError =
new VastError(VastErrorCodes.WRAPPER_LIMIT_REACHED);
return expect(vastPromise).rejects.toEqual(expectedError);
});
Apparently these are similar, but I don't understand the difference that cause the jest infinite loop...
Ok, I've understand the problem.
The cause is the mono thread nature of js.
In the two examples of the edit section, te first one have a timeout so there is a moment whent jest take the control and could check the timeout.
In the second one no, so jest never check the timeout.
In my real case, the problem was the fake server: it was created as:
server = sinon.fakeServer.create({
respondImmediately: true
});
respondImmediately make sinon respond syncroniously, so jest never have the control.
Creating it as:
server = sinon.fakeServer.create({
autoRespond: true
});
sinon respond after 10ms and jest can check the time passing