How to use generateEmptyCoverage method in Jest

This should work. To pipe data to a request you have to tell the readable stream to pipe to the request. The other way is for receiving data from the server. This also uses done instead of async as pipes do not work with async/await.

Also worth nothing is that by default the pipe will call end and then superagent will call end, resulting in an error about end being called twice. To solve this you have to tell the pipe call not to do that and then call end in the on end event of the stream.

import request from 'supertest'

const testImage = `${__dirname}/../../../assets/test_image.jpg`

describe('Upload endpoint', () => {

  test('Successfully uploads jpg image', (done) => {
      const req = request(app)
          .post(`${ROOT_URL}${endpoints.add_image.route}`)
          .set('Authorization', `Bearer ${process.env.testUserJWT}`)
          .set('content-type', 'application/octet-stream')

      const imgStream = fs.createReadStream(testImage);
      imgStream.on('end', () => req.end(done));
      imgStream.pipe(req, {end: false})
  })
})

Edited to add: this has worked for me with small files. If I try testing it with a large test_image.jpg the request times out.

Upgrade node.js In old version of node they were not handled the catch block of jest file.

It will work from node -v9.11.2 to so on.

I would assume it is not a jest but a normal nodeJS logging issue. Can be solved by using:

const util = require('util')
console.log(util.inspect(myObject, {showHidden: false, depth: null}))

You can use toBeVisible() function from RTL. Here you have docs: https://github.com/testing-library/jest-dom#tobevisible

Example:

// element should not be visible on screen
expect(screen.queryByText('1')).not.toBeVisible();

Enzyme's simulate is looking for an onChange event on your Todo component, and it's not finding one. You don't have onChange specified as a prop, so it would make sense that it's not triggering. Wire up the onChange prop to your component if this is the way you want to test it. From the docs:

Even though the name would imply this simulates an actual event, .simulate() will in fact target the component's prop based on the event you give it. For example, .simulate('click') will actually get the onClick prop and call it.

Try something like this, declare the variable in the describe and reset it in the beforeEach:

describe.only('POST request - missing entry', () => {
// newBlog is the "test" object
let newBlog;

beforeEach(() => {
    newBlog = {
         title: 'Test Title',
         author: 'Foo Bar',
         url: 'www.google.com',
         likes: 100
    }

}}

test('sets "likes" field to 0 when missing', async () => {
    delete newBlog.likes // propagates to next test
    console.log(newBlog)
})

test('returns 400 error when "title" and "url" fields are missing', async () => {
    console.log(newBlog)
})
})

The timeout you specify here needs to be shorter than the default timeout.

The default timeout is 5000 and the framework by default is jasmine in case of jest. You can specify the timeout inside the test by adding

jest.setTimeout(30000);

But this would be specific to the test. Or you can set up the configuration file for the framework.

Configuring Jest

// jest.config.js
module.exports = {
  // setupTestFrameworkScriptFile has been deprecated in
  // favor of setupFilesAfterEnv in jest 24
  setupFilesAfterEnv: ['./jest.setup.js']
}

// jest.setup.js
jest.setTimeout(30000)

See also these threads:

setTimeout per test #5055

Make jasmine.DEFAULT_TIMEOUT_INTERVAL configurable #652

P.S.: The misspelling setupFilesAfterEnv (i.e. setupFileAfterEnv) will also throw the same error.

This example will work if you compile ES6 modules syntax into ES5, because in the end, all module exports belong to the same object, which can be modified.

import { allowThrough } from './allowThrough';
import { ENABLED } from './constants';
import * as constants from './constants';

describe('allowThrough', () => {
    test('success', () => {
        constants.ENABLED = true;

        expect(ENABLED).toBe(true);
        expect(allowThrough({ value: 1 })).toBe(true);
    });

    test('fail, ENABLED === false', () => {
        constants.ENABLED = false;

        expect(ENABLED).toBe(false);
        expect(allowThrough({ value: 1 })).toBe(false);
    });
});

Alternatively, you can switch to raw commonjs require function, and do it like this with the help of jest.mock(...):

const mockTrue = { ENABLED: true };
const mockFalse = { ENABLED: false };

describe('allowThrough', () => {
    beforeEach(() => {
        jest.resetModules();
    });

    test('success', () => {
        jest.mock('./constants', () => mockTrue)
        const { ENABLED } = require('./constants');
        const { allowThrough } = require('./allowThrough');

        expect(ENABLED).toBe(true);
        expect(allowThrough({ value: 1 })).toBe(true);
    });

    test('fail, ENABLED === false', () => {
        jest.mock('./constants', () => mockFalse)
        const { ENABLED } = require('./constants');
        const { allowThrough } = require('./allowThrough');

        expect(ENABLED).toBe(false);
        expect(allowThrough({ value: 1 })).toBe(false);
    });
});

I found an answer on SO from a previous similar question Unexpected token 'import' error while running Jest tests?

Basically I had to change my transformIgnorePatterns array in my jest config from:

transformIgnorePatterns: ["/node_modules/"],

to

transformIgnorePatterns: ["/node_modules/(?!vue-awesome)"],

making sure jest compiles 'vue-awesome' module to use in the test.