test: tests for _readableStream.awaitDrain

Fixes: https://github.com/nodejs/node/issues/8684
PR-URL: https://github.com/nodejs/node/pull/8914
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 20 insertions, 2 deletions

diff --git a/test/parallel/test-stream-pipe-await-drain-push-while-write.js b/test/parallel/test-stream-pipe-await-drain-push-while-write.js
index 1dfdfdb80c..67a8f304c3 100644
--- a/test/parallel/test-stream-pipe-await-drain-push-while-write.js
+++ b/test/parallel/test-stream-pipe-await-drain-push-while-write.js
@@ -1,16 +1,34 @@
 'use strict';
 const common = require('../common');
 const stream = require('stream');
+const assert = require('assert');
+
+const awaitDrainStates = [
+  1, // after first chunk before callback
+  1, // after second chunk before callback
+  0 // resolving chunk pushed after first chunk, awaitDrain is decreased
+];
 
 // A writable stream which pushes data onto the stream which pipes into it,
 // but only the first time it's written to. Since it's not paused at this time,
 // a second write will occur. If the pipe increases awaitDrain twice, we'll
 // never get subsequent chunks because 'drain' is only emitted once.
 const writable = new stream.Writable({
-  write: common.mustCall((chunk, encoding, cb) => {
+  write: common.mustCall(function(chunk, encoding, cb) {
     if (chunk.length === 32 * 1024) { // first chunk
-      readable.push(new Buffer(33 * 1024)); // above hwm
+      const beforePush = readable._readableState.awaitDrain;
+      readable.push(new Buffer(34 * 1024)); // above hwm
+      // We should check if awaitDrain counter is increased.
+      const afterPush = readable._readableState.awaitDrain;
+      assert.strictEqual(afterPush - beforePush, 1,
+                         'Counter is not increased for awaitDrain');
     }
+
+    assert.strictEqual(
+      awaitDrainStates.shift(),
+      readable._readableState.awaitDrain,
+      'State variable awaitDrain is not correct.'
+    );
     cb();
   }, 3)
 });