CODEWITHSUNDEEP
javascriptmockingjestjsserver-side-rendering
Marco
Marco

Reputation: 104

Jest mock - window object

How can I mock window to be undefined?

This will help me out testing some scenarios of SSR.

Is the

Object.defineProperty()

a solution, not quite sure how I could mock it



Thank you for the help in advance.

Upvotes: 1

Views: 2803

Answers (1)

Lin Du
Lin Du

Reputation: 102327

Yes, Object.defineProperty() is a solution.

E.g.

index.ts:

function main() {
  return window;
}

export default main;

index.test.ts:

import main from '.';

describe('60152407', () => {
  it('should return window', () => {
    expect(main()).toBeDefined();
  });
  it('should mock window to be undefined', () => {
    Object.defineProperty(global, 'window', { value: undefined });
    expect(main()).toBeUndefined();
  });
});

unit test results with coverage report:

 PASS  stackoverflow/60152407/index.test.ts
  60152407
    ✓ should return window (2ms)
    ✓ should mock window to be undefined (1ms)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |     100 |      100 |     100 |     100 |                   
 index.ts |     100 |      100 |     100 |     100 |                   
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        3.792s, estimated 5s

jest.config.js:

module.exports = {
  preset: 'ts-jest/presets/js-with-ts',
  testEnvironment: 'enzyme',
  setupFilesAfterEnv: ['jest-enzyme', './jest.setup.js'],
  testMatch: ['**/?(*.)+(spec|test).[jt]s?(x)'],
  verbose: true,
};

Source code: https://github.com/mrdulin/react-apollo-graphql-starter-kit/tree/master/stackoverflow/60152407

Upvotes: 1

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