Ensure we finish setup mock before we use it in Http2ConnectionRoundt…

…ripTest.headersWriteForPeerStreamWhichWasResetShouldNotGoAway (netty#9645)

Motivation:

We did dispatch the client code before we did finish setup the mock and so may end up with org.mockito.exceptions.misusing.UnfinishedStubbingException if the connect happens quickly enough.

See https://ci.netty.io/job/netty-centos6-java8-prb/1637/testReport/junit/io.netty.handler.codec.http2/Http2ConnectionRoundtripTest/headersWriteForPeerStreamWhichWasResetShouldNotGoAway/

Modifications:

First finish setup the mock and the dispatch.

Result:

Fix flacky test

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2ConnectionRoundtripTest.java

@@ -522,18 +522,7 @@ public void headersWriteForPeerStreamWhichWasResetShouldNotGoAway() throws Excep
         final CountDownLatch serverWriteHeadersLatch = new CountDownLatch(1);
         final AtomicReference<Throwable> serverWriteHeadersCauseRef = new AtomicReference<Throwable>();
 
-        final Http2Headers headers = dummyHeaders();
         final int streamId = 3;
-        runInChannel(clientChannel, new Http2Runnable() {
-            @Override
-            public void run() throws Http2Exception {
-                http2Client.encoder().writeHeaders(ctx(), streamId, headers, CONNECTION_STREAM_ID,
-                        DEFAULT_PRIORITY_WEIGHT, false, 0, false, newPromise());
-                http2Client.encoder().writeRstStream(ctx(), streamId, Http2Error.CANCEL.code(), newPromise());
-                http2Client.flush(ctx());
-            }
-        });
-
         doAnswer(new Answer<Void>() {
             @Override
             public Void answer(InvocationOnMock invocationOnMock) throws Throwable {
@@ -544,6 +533,17 @@ public Void answer(InvocationOnMock invocationOnMock) throws Throwable {
             }
         }).when(serverListener).onRstStreamRead(any(ChannelHandlerContext.class), eq(streamId), anyLong());
 
+        final Http2Headers headers = dummyHeaders();
+        runInChannel(clientChannel, new Http2Runnable() {
+            @Override
+            public void run() throws Http2Exception {
+                http2Client.encoder().writeHeaders(ctx(), streamId, headers, CONNECTION_STREAM_ID,
+                        DEFAULT_PRIORITY_WEIGHT, false, 0, false, newPromise());
+                http2Client.encoder().writeRstStream(ctx(), streamId, Http2Error.CANCEL.code(), newPromise());
+                http2Client.flush(ctx());
+            }
+        });
+
         assertTrue(serverSettingsAckLatch.await(DEFAULT_AWAIT_TIMEOUT_SECONDS, SECONDS));
         assertTrue(serverGotRstLatch.await(DEFAULT_AWAIT_TIMEOUT_SECONDS, SECONDS));