What is the best way to simulate a TypeScript enum in my Jest test suite?

In my unit tests, I need to create a mock of an enum. The original enum structure includes fixed values for 'START' and 'END', but the middle options can change over time to represent new features. These changes may involve adding or removing enum options.

To ensure that classes interacting with this enum are functioning correctly without constantly updating my unit tests, I want to use a separate enum specifically for testing purposes. This mocked enum will have stable values for 'START' and 'END', but variable options in between:

enum MockedEnum {
    START = 'start',
    NAME_OF_FIRST = 'nameOfFirst',
    NAME_OF_SECOND = 'nameOfSecond',
    END = 'end'
}

Answer №1

I've discovered a clever solution that hinges on the following snippet of code:

jest.mock('./../../models/original-enum.ts', () => ({
    OriginalEnum: jest.requireActual('./../mocks/mocked-enum').MockedEnum 
}));

Placed at the beginning of a unit test file, this code snippet effectively maps the original enum values to the mocked enum values within that specific test file only.

Despite this mapping, you can still access the mocked enum by using

import { MockedEnum } from './../mocks/mocked-enum'
. This allows you to interact with the mocked enum's options in targeted tests.

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