Test: Add givenMiddleware(middleware)

[vlaurin]

Resolves #112

Example

import {givenMiddleware} from '@quickcase/node-toolkit/test';

test('should resolve with response when response expected', async () => {
  const middleware = (req, res) => res.status(201).json({foo: 'bar'});
  const res = await givenMiddleware(middleware).when({}).expectResponse();
  expect(res).toEqual({
    status: 201,
    body: {foo: 'bar'},
  });
});

test('should resolve with next when next expected', async () => {
  const middleware = (req, res, next) => next('error');
  const next = await givenMiddleware(middleware).when({}).expectNext();
  expect(next).toEqual('error');
});

[gbenadikar]

👍