added test for readable streams

test/server.js

@@ -1,6 +1,7 @@
 const fetchMock = require('../src/server.js');
 const expect = require('chai').expect;
 const http = require('http');
+const sinon = require('sinon');
 const { promisify } = require('util');
 
 describe('nodejs tests', () => {
@@ -19,7 +20,8 @@ describe('nodejs tests', () => {
 
 	require('./runner')(fetchMock, global, require('node-fetch'));
 
-	describe('support for Buffers', () => {
+	describe('support for nodejs body types', () => {
+		afterEach(() => fetchMock.reset());
 		it('can respond with a buffer', () => {
 			fetchMock.mock(/a/, new Buffer('buffer'), { sendAsJson: false });
 			return fetchMock
@@ -29,5 +31,28 @@ describe('nodejs tests', () => {
 					expect(txt).to.equal('buffer');
 				});
 		});
+
+		it('can respond with a readable stream', done => {
+			const { Readable, Writable } = require('stream');
+			const readable = new Readable();
+			const write = sinon.stub().callsFake((chunk, enc, cb) => {
+				cb();
+			});
+			const writable = new Writable({
+				write
+			});
+			readable.push('response string');
+			readable.push(null);
+
+			fetchMock.mock(/a/, readable, { sendAsJson: false });
+			fetchMock.fetchHandler('http://a.com').then(res => {
+				res.body.pipe(writable);
+			});
+
+			writable.on('finish', () => {
+				expect(write.args[0][0].toString('utf8')).to.equal('response string');
+				done();
+			});
+		});
 	});
 });