CODEWITHSUNDEEP
node.jsjestjs
Ryan Payne
Ryan Payne

Reputation: 6331

How do I mock a return value multiple times with different values in the same test?

I've built a module that searches for files using node-glob.

// fileCollector.js
const glob = require('glob');

exports.getFiles = (directory) => {
  return {
    freeMarker: glob.sync(directory + '/**/*.ftl'),
    sass: glob.sync(directory + '/**/*.scss')
  };
};

I'm attempting to write a test so that I can verify that:

  1. Glob was called twice with the correct arguments
  2. The return value of getFiles is correct
// fileCollector.test.js
const glob = require('glob');
const fileCollector = require('fileCollector');

jest.mock('glob');

describe('getFiles', () => {
  it('should get files', () => {
    const files = fileCollector.getFiles('/path/to/files');

    expect(glob.sync.mock.calls).toEqual([['/path/to/files/**/*.ftl'], ['/path/to/files/**/*.scss']]);
    expect(files).toEqual({
      freeMarker: 'INSERT_MOCKED_VALUE_FROM_GLOB',
      sass: 'INSERT_MOCKED_VALUE_FROM_GLOB'
    });
  });
});

How do I mock the return value of glob twice with two separate return values so that I can test the return value of getFiles?

Note: Jest mock module multiple times with different values does not answer my question because it mocks a different value once in separate tests.

Upvotes: 23

Views: 35153

Answers (1)

Ryan Payne
Ryan Payne

Reputation: 6331

Use the mockReturnValueOnce function twice. For example:

glob.sync
  .mockReturnValueOnce(['path/to/file.ftl'])
  .mockReturnValueOnce(['path/to/file.sass']);

Full example:

// fileCollector.test.js
const glob = require('glob');
const fileCollector = require('fileCollector');

jest.mock('glob');

describe('getFiles', () => {
  it('should get files', () => {
    glob.sync
      .mockReturnValueOnce(['path/to/file.ftl'])
      .mockReturnValueOnce(['path/to/file.sass']);

    const files = fileCollector.getFiles('/path/to/files');

    expect(glob.sync.mock.calls).toEqual([['/path/to/files/**/*.ftl'], ['/path/to/files/**/*.scss']]);
    expect(files).toEqual({
      freeMarker: ['path/to/file.ftl'],
      sass: ['path/to/file.sass']
    });
  });
});

Source: Jest - Mock Return Values

Upvotes: 47

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