+tck 2.9 blackbox verification should fully drive publisher

It should not use the helper publisher as it may signal asynchronously
as well as onComplete in undefined ways - we need to control the
publisher in this case because of the very specific test scenario

Author: ktoso

tck/src/main/java/org/reactivestreams/tck/SubscriberBlackboxVerification.java

@@ -15,6 +15,7 @@
 
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import static org.reactivestreams.tck.Annotations.NotVerified;
 import static org.reactivestreams.tck.Annotations.Required;
@@ -224,7 +225,23 @@ public void spec209_blackbox_mustBePreparedToReceiveAnOnCompleteSignalWithPreced
     blackboxSubscriberWithoutSetupTest(new BlackboxTestStageTestRun() {
       @Override
       public void run(BlackboxTestStage stage) throws Throwable {
-        final Publisher<T> pub = createHelperPublisher(0);
+        final Publisher<T> pub = new Publisher<T>() {
+          @Override public void subscribe(final Subscriber<? super T> s) {
+            s.onSubscribe(new Subscription() {
+              private AtomicBoolean completed = new AtomicBoolean();
+
+              @Override public void request(long n) {
+                if (completed.compareAndSet(false, true)) {
+                  s.onComplete(); // Publisher now realises that it is in fact already completed
+                }
+              }
+
+              @Override public void cancel() {
+                // noop, ignore
+              }
+            });
+          }
+        };
 
         final Subscriber<T> sub = createSubscriber();
         final BlackboxSubscriberProxy<T> probe = stage.createBlackboxSubscriberProxy(env, sub);