Jest + react-testing-library: Warning update was not wrapped in act()

I am testing my component wit react-testing-library and test works well. I just can't get rid of this warning, fireEvent should by wrapped in act out-of-the-box, but I tried to wrap it again and it did'nt help.

Here is my test case.

it.only("should start file upload if file is added to the field", async () => {
    jest.useFakeTimers();
    const { getByTestId } = wrapper;
    const file = new File(["filefilefile"], "videoFile.mxf");

    const fileInput = getByTestId("drop-zone").querySelector(
      "input[type='file']"
    );

    fireEvent.change(fileInput, { target: { files: [file] } });

    act(() => {
      jest.runAllTimers();
    });

    await wait(() => {
      expect(
        initialProps.uploadItemVideoFileConnect.calledWith(file, 123)
      ).toBe(true);
    });
  });

Here is the warning

Warning: An update to UploadButtonGridComponent inside a test was not wrapped in act(...).

    When testing, code that causes React state updates should be wrapped into act(...):

    act(() => {
      /* fire events that update state */
    });
    /* assert on the output */

In the source code, fireEvent is already wrapped in act().

The problem may be related to this issue, in which async logic (such as a useEffect) is triggering state changes outside of fireEvent:

https://github.com/kentcdodds/react-testing-library/issues/281

(Without seeing your component implementation it's hard to be sure if this is exactly what's happening in your case.)

Apparently there are plans to include async handling in a future release, so that this won't be a problem.

facebook/jest: Delightful JavaScript Testing., Getting Started. Install Jest using yarn : yarn add --dev jest. Or npm : npm install -- save� Jest definition is - a joking or mocking remark. How to use jest in a sentence. Synonym Discussion of jest.

That issue is caused by many updates inside Component.

I got the same, this is how I solved the issue.

await act( async () => {
 fireEvent.change(fileInput, { target: { files: [file] } });
});

jest, Jest. Delightful JavaScript Testing. Developer Ready: Complete and ready to set-up JavaScript testing solution. Works out of the box� Jest definition, a joke or witty remark; witticism. See more.

So this is hard to summarise but I'll try.

The act warning is simply telling you that there is something happening in your functional component which you're not testing.

Let's say we're rendering a list of todos like so

    <ul>
      {loading ? (
        <p>Fetching todos</p>
      ) : (
        <>
          {appData.todoList.slice(0, 15).map((item) => {
            const { id, title } = item;
            return (
              <li key={id} data-testid={id}>
                <Link to={`/item/${id}`}>{title}</Link>
              </li>
            );
          })}
        </>
      )}
    </ul>

The below test case will throw the act warning

import { waitFor, screen, waitForElementToBeRemoved } from "@testing-library/react";

it("Renders <TodoList /> component", async () => {
    render(<TodoList />);
    await waitFor(() => expect(axios.get).toHaveBeenCalledTimes(1));
    await waitForElementToBeRemoved(() => screen.getByText(/Fetching todos/i));

    expect(axios.get).toHaveBeenCalledTimes(1);
    todos.slice(0, 15).forEach((td) => {
      expect(screen.getByText(td.title)).toBeInTheDocument();
    });
  });

But if you re-order the await lines like so

await waitForElementToBeRemoved(() => screen.getByText(/Fetching todos/i));
await waitFor(() => expect(axios.get).toHaveBeenCalledTimes(1);

The act warning goes away. This makes sense. You get to make sure your users no longer see the loading indicator.

There are other cases so go ahead and read this post from kent Dodds.

https://kentcdodds.com/blog/fix-the-not-wrapped-in-act-warning

Jest Tutorial for Beginners: Getting Started With JavaScript Testing, Jest is a JavaScript test runner, that is, a JavaScript library for creating, running, and structuring tests. Jest ships as an NPM package, you can� Define jest. jest synonyms, jest pronunciation, jest translation, English dictionary definition of jest. n. 1. A playful or frivolous mood or manner: spoken in jest.

add await before act

await act(() => {
      /* fire events that update state */
    });

Jest Crash Course - Unit Testing in JavaScript, We will look at how to setup Jest, different matchers as well as how to test async code Duration: 57:19 Posted: Apr 20, 2018 // jest.config.js module.exports = { transform: {}, }; Babel 6 support. Jest 24 dropped support for Babel 6. We highly recommend you to upgrade to Babel 7, which is actively maintained. However, if you cannot upgrade to Babel 7, either keep using Jest 23 or upgrade to Jest 24 with babel-jest locked at version 23, like in the example below:

Jest, Jest cheatsheet. A quick overview to Jest, a test framework for Node.js. This guide targets Jest v20. #Testing. Quick start. npm install --save-dev jest babel-jest . jest meaning: 1. something that is said or done in order to be funny: 2. intended as a joke and not said…. Learn more.

Jest cheatsheet, In jest definition is - as a joke. How to use in jest in a sentence. The Words of the Week - 6/26/20 The Words of the Week - 6/26/20. Some of the words that defined the week ending June 26, 2020

Jest 🃏 Delightful JavaScript Testing 👩🏻‍💻 Developer Ready: Complete and ready to set-up JavaScript testing solution. Works out of the box for any React project. 🏃🏽 Instant Feedback: Failed tests run first. Fast interactive mode can switch between running all tests or only test files related to changed files.

Comments