jest-test-matrix

jest-test-matrix

A plugin for Jest which helps you test functions accepting different combinations of inputs. Instead of manually writing a test for each possible combination, you will only need to write one.

A quick example:

// file.test.js
import testMatrix from 'jest-test-matrix';

interface CanPayOpts {
  amount: number;
  balance: number;
  status: 'active' | 'locked' | 'expired';
}

function canPay({amount, balance, status}: CanPayOpts){
  if (status === 'locked' || status == 'expired'){
    return false;
  }
  return balance > amount;
}

it('should only allow valid payments', () => {
  expect(
    testMatrix(canPay, {
      amount: [20, 100],
      balance : [50],
      status: ['active', 'locked', 'expired']
    })
  ).toMatchSnapshot();
})

will result in the following snapshot:

// file.test.snap
exports[`should only allow valid payments 1`] = `
.-------------------------------------.
|               canPay                |
|-------------------------------------|
| balance | amount | status  | result |
|---------|--------|---------|--------|
|      50 |     20 | active  | true   |
|         |        | locked  | false  |
|         |        | expired | false  |
|         |    100 | active  | false  |
|         |        | locked  | false  |
|         |        | expired | false  |
'-------------------------------------'
`;

Installation

With npm

npm install -D jest-test-matrix

With yarn

yarn add -D jest-test-matrix

Usage

testMatrix(fn, input) where

• fn: (params: Record<'string', any>) => any: The function you want to test. By default, all the parameters in input are passed as an object. If your function has a different arity, you can always pass an anonymous function wrapping your own function, like so testMatrix({a, b} => fn(a, b), {a: [...], b: [...]}). If your function has a name, it will be used as a title in the matrix snapshot.
• input: Record<'string', any[]>: An object where keys are the names of the parameters you want to test (they will be used as column headers in the snapshot), and values are an array of different possible values for each parameter.

The call to testMatrix should we wrapped in a jest.expect call to generate a snapshot:

expect(
  testMatrix(canPay, {
    amount: [20, 100],
    balance : [50],
    status: ['active', 'locked', 'expired']
  })
).toMatchSnapshot();