Reorder waits and assertions to provide better result assurance

Wait for the failure on the stream to occur instead of the exception on the emitter - this ensures that at least the first message will be sucessfully processed and that a failure did occur before assertions are checked.

In the case where the failure may occur sufficiently late in the test execution such that there is a failure, but not yet an exception. In this case emit one more message and wait for the exception before checking

emitThree was unused and would close close the stream via `.complete()` - repurpose for being able to send one message and not close the stream if successful.

tck/src/main/java/org/eclipse/microprofile/reactive/messaging/tck/channel/overflow/BeanWithFailOverflowStrategy.java

@@ -68,12 +68,9 @@ public Exception exception() {
         return callerException;
     }
 
-    public void emitThree() {
+    public void emitOne() {
         try {
-            emitter.send("1");
-            emitter.send("2");
-            emitter.send("3");
-            emitter.complete();
+            emitter.send("1000");
         } catch (Exception e) {
             callerException = e;
         }

tck/src/main/java/org/eclipse/microprofile/reactive/messaging/tck/channel/overflow/FailOverflowStrategyOverflowTest.java

@@ -43,9 +43,15 @@ public static Archive<JavaArchive> deployment() {
     public void testOverflow() {
         bean.emitALotOfItems();
 
-        await().until(() -> bean.exception() != null);
-        assertThat(bean.output()).doesNotContain("999");
+        await().until(() -> bean.failure() != null);
+        assertThat(bean.failure()).isInstanceOf(Exception.class);
         assertThat(bean.output()).isNotEmpty().hasSizeLessThan(999);
-        assertThat(bean.failure()).isNotNull().isInstanceOf(Exception.class);
+        //If an exception has not yet been thrown after the failure occurred, try one more message
+        if (bean.exception() == null) {
+            bean.emitOne();
+            await().until(() -> bean.exception() != null);
+        }
+        assertThat(bean.exception()).isInstanceOf(IllegalStateException.class);
+
     }
 }