public async Task WhenGetConversationsGetsCalled() { Setup(); var fixture = new Fixture(); _conversationParticipants = fixture.CreateMany <ConversationParticipant>().ToList(); _expectedConversations = fixture.CreateMany <Conversation>().ToList(); ConversationsRepository.Setup(repository => repository.GetConversationParticipantsByUserId(It.IsAny <Guid>())) .ReturnsAsync(_conversationParticipants); ConversationsRepository.Setup(repository => repository.GetConversationsByIds(It.IsAny <IList <Guid> >())) .ReturnsAsync(_expectedConversations).Callback <IList <Guid> >(ids => _usedConversationIds = ids); _conversations = await ConversationsService.GetConversations(_userId); }