Test improvements to reduce race conditions.

A couple more improvements to reduce races.

JAVA-3535

Author: rozza

driver-core/src/test/functional/com/mongodb/internal/operation/ChangeStreamOperationSpecification.groovy

@@ -477,9 +477,13 @@ class ChangeStreamOperationSpecification extends OperationFunctionalSpecificatio
         when:
         helper.killCursor(helper.getNamespace(), cursor.getWrapped().getServerCursor())
         expected = insertDocuments(helper, [3, 4])
+        def results = nextAndClean(cursor, async)
+        if (results.size() < expected.size()) {
+            results.addAll(nextAndClean(cursor, async))
+        }
 
         then:
-        nextAndClean(cursor, async) == expected
+        results == expected
 
         then:
         tryNextAndClean(cursor, async) == null
@@ -488,7 +492,7 @@ class ChangeStreamOperationSpecification extends OperationFunctionalSpecificatio
         expected = insertDocuments(helper, [5, 6])
         helper.killCursor(helper.getNamespace(), cursor.getWrapped().getServerCursor())
 
-        def results = nextAndClean(cursor, async)
+        results = nextAndClean(cursor, async)
         if (results.size() < expected.size()) {
             results.addAll(nextAndClean(cursor, async))
         }

driver-reactive-streams/src/test/functional/com/mongodb/reactivestreams/client/TestSubscriber.java

@@ -166,7 +166,7 @@ public Subscription getSubscription() {
      * @throws AssertionError if the sequence of items observed does not exactly match {@code items}
      */
     public void assertReceivedOnNext(final List<T> items) {
-        if (tryMultipleTimes(2, () -> getOnNextEvents().size() != items.size())) {
+        if (tryMultipleTimes(items.size(), () -> getOnNextEvents().size() != items.size())) {
             throw new AssertionError("Number of items does not match. Provided: " + items.size() + "  Actual: " + getOnNextEvents().size());
         }