diff -r 2c3cc4b01880 -r c16ac7a2eba4 test/jdk/jdk/jfr/api/consumer/recordingstream/TestOnFlush.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/jdk/jfr/api/consumer/recordingstream/TestOnFlush.java	Wed Oct 30 19:43:52 2019 +0100
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.jfr.api.consumer.recordingstream;
+
+import java.util.concurrent.CountDownLatch;
+
+import jdk.jfr.Event;
+import jdk.jfr.consumer.RecordingStream;
+
+/**
+ * @test
+ * @summary Tests RecordingStream::onFlush(...)
+ * @key jfr
+ * @requires vm.hasJFR
+ * @library /test/lib
+ * @run main/othervm jdk.jfr.api.consumer.recordingstream.TestOnFlush
+ */
+public class TestOnFlush {
+
+    static class OneEvent extends Event {
+    }
+
+    public static void main(String... args) throws Exception {
+        testOnFlushNull();
+        testOneEvent();
+        testNoEvent();
+    }
+
+    private static void testOnFlushNull() {
+        log("Entering testOnFlushNull()");
+        try (RecordingStream rs = new RecordingStream()) {
+           try {
+               rs.onFlush(null);
+               throw new AssertionError("Expected NullPointerException from onFlush(null");
+           } catch (NullPointerException npe) {
+               // OK; as expected
+           }
+        }
+        log("Leaving testOnFlushNull()");
+     }
+
+    private static void testNoEvent() throws Exception {
+        log("Entering testNoEvent()");
+        CountDownLatch flush = new CountDownLatch(1);
+        try (RecordingStream r = new RecordingStream()) {
+            r.onFlush(() -> {
+                flush.countDown();
+            });
+            r.startAsync();
+            flush.await();
+        }
+        log("Leaving testNoEvent()");
+    }
+
+    private static void testOneEvent() throws InterruptedException {
+        log("Entering testOneEvent()");
+        CountDownLatch flush = new CountDownLatch(1);
+        try (RecordingStream r = new RecordingStream()) {
+            r.onEvent(e -> {
+                // ignore event
+            });
+            r.onFlush(() -> {
+                flush.countDown();
+            });
+            r.startAsync();
+            OneEvent e = new OneEvent();
+            e.commit();
+            flush.await();
+        }
+        log("Leaving testOneEvent()");
+    }
+
+    private static void log(String msg) {
+        System.out.println(msg);
+    }
+}