How to use jest test.each function

Let’s test with Jest the following isInfiniteDate function, which checks whether the given date is “infinite” in the given context:

export const isInfiniteDate = (input: string): boolean => {
    const maximumDatePossible = '9999-12-31';
    return new Date(input).getTime() === new Date(maximumDatePossible).getTime();
};

For sure, we want to test different dates with the same expected result, either true or false

To avoid “duplication” of same test with different data, you can use test.each(table)(name, fn, timeout) function, to which you can pass an Array of Arrays with the arguments that are passed into the test fn for each row.

describe('isInfiniteDate > ', () => {
    test.each([
        [null, false],
        [undefined, false],
        ['AXON', false],
        ['2021-31-31', false],
        ['2021-12-12', false],
        ['9999-12-31', true],
    ])('given input date %p , it should return %p ', (input, expected) => {
        expect(isInfiniteDate(input)).toEqual(expected);
    });
});
  • name is the String title of the test block - See the referenced link for the different formatting options
  • optionally, you can provide a timeout (in milliseconds) for specifying how long to wait for each row before aborting. The default timeout is 5 seconds.

This is the equivalent of @ParameterizedTest in Java

Reference - https://jestjs.io/docs/api#testeachtablename-fn-timeout


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Adrian Matei (aka adixchen)

Adrian Matei (aka adixchen)
Life force expressing itself as a coding capable human being

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Published on December 14, 2022