test: stream readableListening internal state

PR-URL: https://github.com/nodejs/node/pull/9864
Refs: https://github.com/nodejs/node/issues/8683
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-stream-readableListening-state.js

@@ -0,0 +1,34 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const stream = require('stream');
+
+const r = new stream.Readable({
+  read: () => {}
+});
+
+// readableListening state should start in `false`.
+assert.strictEqual(r._readableState.readableListening, false);
+
+r.on('readable', common.mustCall(() => {
+  // Inside the readable event this state should be true.
+  assert.strictEqual(r._readableState.readableListening, true);
+}));
+
+r.push(Buffer.from('Testing readableListening state'));
+
+const r2 = new stream.Readable({
+  read: () => {}
+});
+
+// readableListening state should start in `false`.
+assert.strictEqual(r2._readableState.readableListening, false);
+
+r2.on('data', common.mustCall((chunk) => {
+  // readableListening should be false because we don't have
+  // a `readable` listener
+  assert.strictEqual(r2._readableState.readableListening, false);
+}));
+
+r2.push(Buffer.from('Testing readableListening state'));