Added test for relation operations

packages/dart/test/relation_test.dart

@@ -0,0 +1,119 @@
+import 'dart:convert';
+
+import 'package:parse_server_sdk/parse_server_sdk.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Relation', () {
+    test('addRelation', () async {
+      // arrange
+      await Parse().initialize('appId', 'https://test.parse.com',
+          debug: true,
+          // to prevent automatic detection
+          fileDirectory: 'someDirectory',
+          // to prevent automatic detection
+          appName: 'appName',
+          // to prevent automatic detection
+          appPackageName: 'somePackageName',
+          // to prevent automatic detection
+          appVersion: 'someAppVersion',
+          registeredSubClassMap: <String, ParseObjectConstructor>{
+            PostModel.keyClassName: () => PostModel(),
+            LikeModel.keyClassName: () => LikeModel(),
+          });
+
+      String res =
+          "{\"objectId\":\"mGGxAy3eek\",\"Likes\":{\"__type\":\"Relation\",\"className\":\"Like\"}}";
+      Map<String, dynamic> map = json.decode(res);
+
+      final PostModel post = PostModel.clone().fromJson(map);
+      final LikeModel like = LikeModel();
+      like.objectId = "like1";
+      final LikeModel like2 = LikeModel();
+      like2.objectId = "like2";
+
+      like.onPost = post;
+      like2.onPost = post;
+
+      post.likeRelation.add(like); // or post.addRelation('likes', [post]);
+      post.likeRelation.add(like2); // or post.addRelation('likes', [post]);
+
+      // desired output
+      String expectedResult =
+          "{\"Likes\":{\"__op\":\"AddRelation\",\"objects\":[{\"__type\":\"Pointer\",\"className\":\"Like\",\"objectId\":\"like1\"},{\"__type\":\"Pointer\",\"className\":\"Like\",\"objectId\":\"like2\"}]}}";
+      // act
+      dynamic actualResult = post.encode();
+      //assert
+      expect(actualResult.toString(), expectedResult);
+    });
+  });
+  test('removeRelation', () async {
+    // arrange
+    await Parse().initialize('appId', 'https://test.parse.com',
+        debug: true,
+        // to prevent automatic detection
+        fileDirectory: 'someDirectory',
+        // to prevent automatic detection
+        appName: 'appName',
+        // to prevent automatic detection
+        appPackageName: 'somePackageName',
+        // to prevent automatic detection
+        appVersion: 'someAppVersion',
+        registeredSubClassMap: <String, ParseObjectConstructor>{
+          PostModel.keyClassName: () => PostModel(),
+          LikeModel.keyClassName: () => LikeModel(),
+        });
+
+    String res =
+        "{\"objectId\":\"mGGxAy3eek\",\"Likes\":{\"__type\":\"Relation\",\"className\":\"Like\"}}";
+    Map<String, dynamic> map = json.decode(res);
+
+    final PostModel post = PostModel.clone().fromJson(map);
+    LikeModel like = LikeModel();
+    like.objectId = "like";
+    post.likeRelation.remove(like);
+
+    // desired output
+    String expectedResult =
+        "{\"Likes\":{\"__op\":\"RemoveRelation\",\"objects\":[{\"__type\":\"Pointer\",\"className\":\"Like\",\"objectId\":\"like\"}]}}";
+    // act
+    dynamic actualResult = post.encode();
+    //assert
+    expect(actualResult.toString(), expectedResult);
+  });
+}
+
+class PostModel extends ParseObject implements ParseCloneable {
+  static const String keyClassName = 'Post';
+  static const String keyRelationLike = "Likes";
+
+  PostModel() : super(keyClassName);
+
+  PostModel.clone() : this();
+
+  @override
+  clone(Map<String, dynamic> map) => PostModel.clone()..fromJson(map);
+
+  ParseRelation<LikeModel> get likeRelation =>
+      getRelation<LikeModel>(keyRelationLike);
+
+  String encode() => json.encode(toJson(forApiRQ: true));
+}
+
+class LikeModel extends ParseObject implements ParseCloneable {
+  static const String keyClassName = 'Like';
+  static const String _keyOnPost = "OnPost";
+
+  LikeModel() : super(keyClassName);
+
+  LikeModel.clone() : this();
+
+  @override
+  clone(Map<String, dynamic> map) => LikeModel.clone()..fromJson(map);
+
+  PostModel? get onPost => get<PostModel>(_keyOnPost);
+
+  set onPost(PostModel? post) {
+    if (post != null) set<PostModel>(_keyOnPost, post);
+  }
+}