invalidCommand.js

    it('fails with invalid command', function (done) {
      yargs('marsupial -w 10')
        .command('marsupial', 'wombat burrows', function (yargs, argv) {
          console.log(argv)
          return argv
        })
        .demand(1, ['w', 'b'])
        .strict()
        .fail(function (msg) {
          msg.should.equal('Missing required argument: b')
          return done()
        })
        .argv
    })