JS Unit testing run multiple times with different parameters

Question

Is their any way to have multiple parameters in one test instead of copying and pasting the function again?

Example in NUnit for C#:

[TestCase("0", 1)]
[TestCase("1", 1)]
[TestCase("2", 1)]
public void UnitTestName(string input, int expected)
{
    //Arrange

    //Act

    //Assert
}

What I want in Js:

describe("<Foo />", () => {

    [TestCase("false")]
    [TestCase("true")]
    it("option: enableRemoveControls renders remove controls", (enableRemoveControls) =>  {
        mockFoo.enableRemoveControls = enableRemoveControls;

        //Assert that the option has rendered or not rendered the html
    });
});

Just make a new function and call it, I guess. In general, since you are passing a callback to `it` (and `describe`, etc) you can just make a function that returns a callback `function makeTest(input, expected) { return function() { assert(input === expected)})` then just call it in your tests `it("passes", makeTest(1, 1))` and vary the arguments `it("fails", makeTest("apple", "orange"))` — VLAZ, Oct 26 '16 at 22:14

score 65 · Accepted Answer · edited Feb 20 '23 at 22:37

65

An alternative is to use Jest. It has this functionality built-in:

test.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

edited Feb 20 '23 at 22:37

Chris

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answered Jun 04 '18 at 15:17

Asen Arizanov

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Tagged templates used in such a smart way! love it – Marcin Apr 24 '19 at 11:39
Thanks for this. Amazing api :) – uloco Sep 10 '19 at 14:53
This is great! :) – n.sh Feb 02 '21 at 10:06
Looks like `test.each` was added in Jest version 23.X – ElliotSchmelliot Sep 27 '21 at 22:41
is it just me or this doesn't tell you which case failed? (but just says it fails – the pillow Dec 15 '21 at 03:06

score 15 · Answer 2 · answered Oct 26 '16 at 22:12

You can put the it-call inside a function and call it with different parameters:

describe("<Foo />", () => {

    function run(enableRemoveControls){
        it("option: enableRemoveControls renders remove controls", () =>  {
            mockFoo.enableRemoveControls = enableRemoveControls;

            //Assert that the option has rendered or not rendered the html
        });
    }

    run(false);
    run(true);
});

score 3 · Answer 3 · answered Jan 07 '19 at 11:05

If you're using Mocha you can combine it with mocha-testdata:

import * as assert from assert;
import { given } from mocha-testdata;

describe('<Foo />', function () {
    given([
        { input: true,  expected: 'some expected value',       description: 'flag enabled' },
        { input: false, expected: 'some other expected value', description: 'flag disabled' },
    ]).
    it('option: enableRemoveControls renders remove controls', function ({ input, expected }) {
        // prepare, act, assert
    });
});

In the above sample you'll also notice a description field that's not being injected into the test. This little trick can be used to make the reported test name more meaningful.

Hope this helps!

Jan

JS Unit testing run multiple times with different parameters

3 Answers3