typescript alias options not parsing off CommandModule in jest

I’m trying to test some modules of yargs and noticed in my jest tests that yargs didn’t seem to be processing aliases on options like I expected. Below I expect the option ‘flag’ to end up making argv entries ‘flag’ and ‘f’, the alias. Instead it seems to not process the flag on my builder. How can I ensure my CommandModule tests work with alias options? PS is this the best way to drive this code path?

mkdir tmp/
cd tmp/
npm init -y
npm install jest typescript yargs ts-jest

jest.config.js

module.exports = {
	  transform: {'^.+\\.ts?$': 'ts-jest'},
	  testEnvironment: 'node',
	  testRegex: '.*\\.(test|spec)?\\.(ts|tsx)$',
	  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node']
};

yargs.test.ts

import yargs = require('yargs');
import { Arguments, CommandModule } from 'yargs';
const spyConsole = jest.spyOn(console, 'log').mockImplementation();

interface MyArgs extends Arguments {
  flag: string;
  f?: string;
}

const flagCmd: CommandModule = {
  command: 'flag it',
  describe: 'flag a flag',
  builder: {
    flag: {
      type: 'boolean',
      description: 'Boolean Flag',
      alias: 'f',
      default: false,
    },
  },
  handler: async (argv: MyArgs) => {
    console.log(JSON.stringify(argv));
  },
};

it('parses an alias for the test', async () => {
  await flagCmd.handler(yargs(['-f']).command(flagCmd).parse());
  expect(spyConsole.mock.calls.length).toBe(1);
  expect(spyConsole.mock.calls[0][0]).toContain('"f":true');
  expect(spyConsole.mock.calls[0][0]).toContain('"flag":true');
});

node node_modules/jest/bin/jest.js yargs.test.ts
# returns a fail because the "flag":true key is missing.

[joekiller]

With my newly discovered onFinishCommand this now works with the following:

import * as yargs from 'yargs';
import { Arguments, CommandModule } from 'yargs';
const spyConsole = jest.spyOn(console, 'log').mockImplementation();

interface MyArgs extends Arguments {
  flag: string;
  f?: string;
}

const flagCmd: CommandModule = {
  command: 'flag',
  describe: 'flag a flag',
  builder: {
    flag: {
      type: 'boolean',
      description: 'Boolean Flag',
      alias: 'f',
      default: false,
    },
  },
  handler: async (argv: MyArgs) => {
    console.log(JSON.stringify(argv));
    return Promise.resolve(argv);
  },
};

it('parses an alias for the test', async (done) => {
  await new Promise((resolve, reject) => {
    try {
      yargs
        .command(flagCmd)
        .onFinishCommand(async (r) => resolve(r))
        .exitProcess(false)
        .parse('flag -f');
    } catch (e) {
      reject(e);
    }
  });
  expect(spyConsole.mock.calls.length).toBe(1);
  expect(spyConsole.mock.calls[0][0]).toContain('"f":true');
  expect(spyConsole.mock.calls[0][0]).toContain('"flag":true');
  done();
});

[jltwheeler]

Thanks @joekiller! So this method works perfectly with testing your command error handling in jest!