test: keep test/parallel/test-stream-pipe-flow

Refs: nodejs#18515
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-stream-pipe-flow.js

@@ -0,0 +1,67 @@
+'use strict';
+const common = require('../common');
+const { Readable, Writable, PassThrough } = require('stream');
+
+{
+  let ticks = 17;
+
+  const rs = new Readable({
+    objectMode: true,
+    read: () => {
+      if (ticks-- > 0)
+        return process.nextTick(() => rs.push({}));
+      rs.push({});
+      rs.push(null);
+    }
+  });
+
+  const ws = new Writable({
+    highWaterMark: 0,
+    objectMode: true,
+    write: (data, end, cb) => setImmediate(cb)
+  });
+
+  rs.on('end', common.mustCall());
+  ws.on('finish', common.mustCall());
+  rs.pipe(ws);
+}
+
+{
+  let missing = 8;
+
+  const rs = new Readable({
+    objectMode: true,
+    read: () => {
+      if (missing--) rs.push({});
+      else rs.push(null);
+    }
+  });
+
+  const pt = rs
+    .pipe(new PassThrough({ objectMode: true, highWaterMark: 2 }))
+    .pipe(new PassThrough({ objectMode: true, highWaterMark: 2 }));
+
+  pt.on('end', function() {
+    wrapper.push(null);
+  });
+
+  const wrapper = new Readable({
+    objectMode: true,
+    read: () => {
+      process.nextTick(function() {
+        let data = pt.read();
+        if (data === null) {
+          pt.once('readable', function() {
+            data = pt.read();
+            if (data !== null) wrapper.push(data);
+          });
+        } else {
+          wrapper.push(data);
+        }
+      });
+    }
+  });
+
+  wrapper.resume();
+  wrapper.on('end', common.mustCall());
+}