public void EditMessageByAdmin_MessageChangeText()
        {
            StubUser admin = new StubUser(Guid.NewGuid());

            StubUser[] admins = new StubUser[] { admin };
            StubUser   user   = new StubUser(Guid.NewGuid());

            StubUser[] users = new StubUser[] { user };
            GroupChat  chat  = new GroupChat(
                Guid.NewGuid(),
                new List <Message>(),
                new List <IUser>(users),
                new List <IUser>(admins));
            Message message = new Message(Guid.NewGuid(), user, "hello");
            string  newText = "NewHello";

            chat.EditMessage(message.Id, admin, newText);

            foreach (Message mes in chat.Messages)
            {
                Assert.IsTrue(mes.Text == newText);
            }
        }