fix: correctly re-establishes pipe destinations (#2592)

reenable tests in master for reestablishing piped destinations
after a change stream resumes

NODE-2172

test/functional/change_stream.test.js

@@ -1,4 +1,5 @@
 'use strict';
+const path = require('path');
 const assert = require('assert');
 const { Transform, PassThrough } = require('stream');
 const { MongoNetworkError } = require('../../src/error');
@@ -1454,8 +1455,7 @@ describe('Change Streams', function () {
     }
   });
 
-  // TODO: resuming currently broken on piped change streams, fix as part of NODE-2172
-  it.skip('should resume piping of Change Streams when a resumable error is encountered', {
+  it('should resume piping of Change Streams when a resumable error is encountered', {
     metadata: {
       requires: {
         generators: true,
@@ -1464,11 +1464,10 @@ describe('Change Streams', function () {
       }
     },
     test: function (done) {
+      const filename = path.join(__dirname, '_nodemongodbnative_resumepipe.txt');
+      this.defer(() => fs.unlinkSync(filename));
       const configuration = this.configuration;
 
-      // Contain mock server
-      let primaryServer = null;
-
       // Default message fields
       const defaultFields = {
         setName: 'rs',
@@ -1484,9 +1483,8 @@ describe('Change Streams', function () {
         hosts: ['localhost:32000', 'localhost:32001', 'localhost:32002']
       };
 
-      co(function* () {
-        primaryServer = yield mock.createServer();
-
+      mock.createServer(32000, 'localhost').then(primaryServer => {
+        this.defer(() => mock.cleanup());
         let counter = 0;
         primaryServer.setMessageHandler(request => {
           const doc = request.document;
@@ -1572,31 +1570,26 @@ describe('Change Streams', function () {
 
         client.connect((err, client) => {
           expect(err).to.not.exist;
+          this.defer(() => client.close());
 
           const database = client.db('integration_tests5');
           const collection = database.collection('MongoNetworkErrorTestPromises');
           const changeStream = collection.watch(pipeline);
 
-          const filename = '/tmp/_nodemongodbnative_resumepipe.txt';
           const outStream = fs.createWriteStream(filename);
 
           changeStream.stream({ transform: JSON.stringify }).pipe(outStream);
-
+          this.defer(() => changeStream.close());
           // Listen for changes to the file
-          const watcher = fs.watch(filename, function (eventType) {
-            assert.equal(eventType, 'change');
+          const watcher = fs.watch(filename, eventType => {
+            this.defer(() => watcher.close());
+            expect(eventType).to.equal('change');
 
             const fileContents = fs.readFileSync(filename, 'utf8');
             const parsedFileContents = JSON.parse(fileContents);
-            assert.equal(parsedFileContents.fullDocument.a, 1);
-
-            watcher.close();
+            expect(parsedFileContents).to.have.nested.property('fullDocument.a', 1);
 
-            changeStream.close(err => {
-              expect(err).to.not.exist;
-
-              mock.cleanup(() => done());
-            });
+            done();
           });
         });
       });