public async Task UserLeft_UserNull()
        {
            //assemble
            var queryContext        = AssembleMocks.GetQueryContext();
            var commandContext      = AssembleMocks.GetCommandContext();
            var userSummaryRepo     = new UserSummaryRepository(queryContext.Object);
            var conversationRepo    = new ConversationRepository(queryContext.Object, commandContext.Object);
            var messageRepo         = new MessageRepository(queryContext.Object, commandContext.Object);
            var conversationContext = new ConversationBoundedContext(conversationRepo, userSummaryRepo, messageRepo);
            var conversation        = await conversationContext.GetById(4);

            var userSummary = await userSummaryRepo.GetById(1);

            var userSummaryTest = await userSummaryRepo.GetById(5);

            conversation.UserJoined(userSummary); //workaround since can't seem to mock a working Include()
            Assert.IsTrue(conversation.ActiveUsers.Count() == 1);

            //act
            conversation.UserLeft(userSummaryTest);

            //assert
            Assert.IsNull(userSummaryTest);
            Assert.IsTrue(conversation.ActiveUsers.Count() == 1);
        }
        public async Task UserJoined_UserNull()
        {
            //assemble
            var queryContext        = AssembleMocks.GetQueryContext();
            var commandContext      = AssembleMocks.GetCommandContext();
            var userSummaryRepo     = new UserSummaryRepository(queryContext.Object);
            var conversationRepo    = new ConversationRepository(queryContext.Object, commandContext.Object);
            var messageRepo         = new MessageRepository(queryContext.Object, commandContext.Object);
            var conversationContext = new ConversationBoundedContext(conversationRepo, userSummaryRepo, messageRepo);
            var conversation        = await conversationContext.GetById(5);

            var userSummary = await userSummaryRepo.GetById(5);

            //act
            conversation.UserJoined(userSummary);

            //assert
            Assert.IsNull(userSummary);
            Assert.IsTrue(conversation.ActiveUsers.Count() == 0);
        }