PostActionTransformation.cs

        public class PostActionTransformation<T> : ISpecimenBuilderTransformation
        {
            private readonly List<ISpecimenCommand> _commands = new List<ISpecimenCommand>();

            public ISpecimenBuilder Transform(ISpecimenBuilder builder)
            {
                return new Postprocessor(
                    builder,
                    new CompositeSpecimenCommand(_commands),
                    new IsAssignableToTypeSpecification(typeof(T)));
            }

            public PostActionTransformation<T> With<TProperty>(Expression<Func<T, TProperty>> propertyPicker,
                TProperty value)
            {
                _commands.Add(new BindingCommand<T, TProperty>(propertyPicker, value));

                return this;
            }

            public PostActionTransformation<T> Do(Action<T, ISpecimenContext> func)
            {
                _commands.Add(new ActionSpecimenCommand<T>(func));
                return this;
            }
        }