public void cannot_add_duplicate()
        {
            // Arrange
            var training    = new Training();
            var participant = new Participant
            {
                Id        = _fixture.Create <int>(),
                Email     = _fixture.Create <string>(),
                FirstName = _fixture.Create <string>(),
                LastName  = _fixture.Create <string>(),
            };

            training.AddParticipant(participant);

            // Act
            training.AddParticipant(participant);

            // Assert
            var result = training
                         .Participants
                         .Count(i => i.Id == participant.Id);

            result
            .Should()
            .Be(1);
        }
        public void if_added_can_be_retrieved_from_collection()
        {
            // Arrange
            var training    = new Training();
            var participant = new Participant
            {
                Id        = _fixture.Create <int>(),
                Email     = _fixture.Create <string>(),
                FirstName = _fixture.Create <string>(),
                LastName  = _fixture.Create <string>(),
            };

            var p = new Participant();

            p.Id    = 1;
            p.Email = "@";

            // Act
            training.AddParticipant(participant);

            // Assert
            training
            .Participants
            .FirstOrDefault(i => i.Id == participant.Id)
            .Should()
            .NotBeNull();
        }