Add unit test coverage for ServerCall triggerEvent and custom events framework.

- Added unit tests in AbstractServerStreamTest for triggerEvent propagation and close behavior.
- Updated ContextsTest to cover onEvent propagation in ContextualizedServerCallListener.

TAG=agy
CONV=e1bfa5a2-e855-4f79-abdd-ef2b264977be

Author: kannanjgithub

api/src/test/java/io/grpc/ContextsTest.java

@@ -82,6 +82,11 @@ public void interceptCall_basic() {
         assertSame(uniqueContext, Context.current());
         methodCalls.add(5);
       }
+
+      @Override public void onEvent(Object event) {
+        assertSame(uniqueContext, Context.current());
+        methodCalls.add(6);
+      }
     };
     ServerCall.Listener<Object> wrapped = interceptCall(uniqueContext, call, headers,
         new ServerCallHandler<Object, Object>() {
@@ -101,7 +106,8 @@ public ServerCall.Listener<Object> startCall(
     wrapped.onCancel();
     wrapped.onComplete();
     wrapped.onReady();
-    assertEquals(Arrays.asList(1, 2, 3, 4, 5), methodCalls);
+    wrapped.onEvent(new Object());
+    assertEquals(Arrays.asList(1, 2, 3, 4, 5, 6), methodCalls);
     assertSame(origContext, Context.current());
   }
 
@@ -145,6 +151,10 @@ public void interceptCall_restoresIfListenerThrows() {
       @Override public void onReady() {
         throw new RuntimeException();
       }
+
+      @Override public void onEvent(Object event) {
+        throw new RuntimeException();
+      }
     };
     ServerCall.Listener<Object> wrapped = interceptCall(uniqueContext, call, headers,
         new ServerCallHandler<Object, Object>() {
@@ -180,6 +190,11 @@ public ServerCall.Listener<Object> startCall(
       fail("Exception expected");
     } catch (RuntimeException expected) {
     }
+    try {
+      wrapped.onEvent(new Object());
+      fail("Exception expected");
+    } catch (RuntimeException expected) {
+    }
     assertSame(origContext, Context.current());
   }
 

core/src/test/java/io/grpc/internal/AbstractServerStreamTest.java

@@ -361,6 +361,31 @@ public void close_sendTrailersClearsReservedFields() {
     assertEquals("bad", metadataCaptor.getValue().get(InternalStatus.MESSAGE_KEY));
   }
 
+  @Test
+  public void triggerEvent_propagatesToListener() {
+    ServerStreamListener listener = mock(ServerStreamListener.class);
+    stream.transportState().setListener(listener);
+
+    Object event = new Object();
+    stream.triggerEvent(event);
+
+    verify(listener).triggerEvent(event);
+  }
+
+  @Test
+  public void triggerEvent_ignoredAfterClose() {
+    ServerStreamListener listener = mock(ServerStreamListener.class);
+    stream.transportState().setListener(listener);
+
+    stream.close(Status.OK, new Metadata());
+    stream.transportState().complete();
+
+    Object event = new Object();
+    stream.triggerEvent(event);
+
+    verify(listener, never()).triggerEvent(any());
+  }
+
   @Test
   public void changeOnReadyThreshold() {
     stream.setListener(new ServerStreamListenerBase());