xmpp: Communicate stream closure from the buffer

test/xmlstreambuffer_test.dart

@@ -54,4 +54,37 @@ void main() {
       expect(childb, true);
     });
   });
+
+  test("Test closing the stream", () async {
+    bool childa = false;
+    bool childb = false;
+    bool closed = false;
+
+    final buffer = XmlStreamBuffer();
+    final controller = StreamController<String>();
+
+    controller
+    .stream
+    .transform(buffer)
+    .forEach((node) {
+      if (node.tag == "childa") {
+        childa = true;
+      } else if (node.tag == "childb") {
+        childb = true;
+      } else if (node.tag == "stream:stream" && node.children.isEmpty) {
+        assert (childa);
+        assert (childb);
+        closed = true;
+      }
+    });
+    controller.add("<childa");
+    controller.add(" /><childb />");
+    controller.add("</stream:stream>");
+
+    await Future.delayed(const Duration(seconds: 2), () {
+      expect(childa, true);
+      expect(childb, true);
+      expect(closed, true);
+    });
+  });
 }