fix: fix custom request instantiation (#191)

Custom requests should preserve the stream attributes of the request,
namely the `_readableState` property inherited from `Readable`.

lib/request.js

@@ -54,13 +54,14 @@ class MockSocket extends EventEmitter {
  * @param {any} [options.payload]
  */
 function CustomRequest (options) {
-  return new _CustomLMRRequest()
+  return new _CustomLMRRequest(this)
 
-  function _CustomLMRRequest () {
-    Request.call(this, {
+  function _CustomLMRRequest (obj) {
+    Request.call(obj, {
       ...options,
       Request: undefined
     })
+    Object.assign(this, obj)
 
     for (const fn of Object.keys(Request.prototype)) {
       this.constructor.prototype[fn] = Request.prototype[fn]

test/test.js

@@ -112,6 +112,19 @@ test('request inherits from custom class', (t) => {
   })
 })
 
+test('request with custom class preserves stream data', (t) => {
+  t.plan(2)
+  const dispatch = function (req, res) {
+    t.ok(req._readableState)
+    res.writeHead(200)
+    res.end()
+  }
+
+  inject(dispatch, { method: 'GET', url: 'http://example.com:8080/hello', Request: http.IncomingMessage }, (err, res) => {
+    t.error(err)
+  })
+})
+
 test('assert Request option has a valid prototype', (t) => {
   t.plan(2)
   const dispatch = function (req, res) {