test case added

packages/firebase_database/firebase_database/test/firebase_sorted_list_test.dart

@@ -0,0 +1,99 @@
+
+import 'dart:async';
+
+import 'package:firebase_database/firebase_database.dart';
+import 'package:firebase_database/ui/firebase_sorted_list.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'firebase_list_test.dart';
+
+void main() {
+
+  group('FirebaseSortedList', () {
+    late StreamController<DatabaseEvent> onChildAddedStreamController;
+    late StreamController<DatabaseEvent> onChildRemovedStreamController;
+    late StreamController<DatabaseEvent> onChildChangedStreamController;
+    late StreamController<DatabaseEvent> onChildMovedStreamController;
+    late StreamController<DatabaseEvent> onValue;
+    late MockQuery query;
+    late FirebaseSortedList list;
+    late Completer<ListChange> callbackCompleter;
+
+    setUp(() {
+      onChildAddedStreamController = StreamController<DatabaseEvent>();
+      onChildRemovedStreamController = StreamController<DatabaseEvent>();
+      onChildChangedStreamController = StreamController<DatabaseEvent>();
+      onChildMovedStreamController = StreamController<DatabaseEvent>();
+      onValue = StreamController<DatabaseEvent>();
+      query = MockQuery(
+        onChildAddedStreamController.stream,
+        onChildRemovedStreamController.stream,
+        onChildChangedStreamController.stream,
+        onChildMovedStreamController.stream,
+        onValue.stream,
+      );
+      callbackCompleter = Completer<ListChange>();
+
+      void completeWithChange(int index, DataSnapshot snapshot) {
+        callbackCompleter.complete(ListChange.at(index, snapshot));
+      }
+
+      list = FirebaseSortedList(
+        query: query,
+        onChildAdded: completeWithChange,
+        onChildRemoved: completeWithChange,
+        onChildChanged: completeWithChange,
+        comparator: (DataSnapshot a, DataSnapshot b) {
+          return b.key.toString().compareTo(a.key.toString());
+        },
+      );
+    });
+
+    tearDown(() {
+      onChildAddedStreamController.close();
+      onChildRemovedStreamController.close();
+      onChildChangedStreamController.close();
+      onChildMovedStreamController.close();
+      onValue.close();
+    });
+
+    Future<ListChange> resetCompleterOnCallback() async {
+      final ListChange result = await callbackCompleter.future;
+      callbackCompleter = Completer<ListChange>();
+      return result;
+    }
+
+    Future<ListChange> processChildAddedEvent(DatabaseEvent event) {
+      onChildAddedStreamController.add(event);
+
+
+
+      final future =  resetCompleterOnCallback();
+
+      expect(list.indexOf(event.snapshot), isNot(equals(-1)));
+
+
+      return future;
+
+    }
+
+    test('can push to sorted list', () async {
+      final DataSnapshot snapshot = MockDataSnapshot('key10', 10);
+      expect(
+        await processChildAddedEvent(
+          MockEvent(
+            DatabaseEventType.childAdded,
+            null,
+            snapshot,
+          ),
+        ),
+        ListChange.at(0, snapshot),
+      );
+      expect(list, <DataSnapshot>[snapshot]);
+    });
+
+  });
+
+}
+
+