The advertisement somehow worked in our team from the third attempt, so I am to share it here, too.

https://hexdocs.pm/estructura/Estructura.User.html

Elixir structs with coercion, validation, access, and data generation for property tests.

iex|%_{}|1 ▶ Estructura.User.__generator__ |> Enum.take(1)
[
%Estructura.User{
address: %Estructura.User.Address{
city: "4",
street: %Estructura.User.Address.Street{house: "a", name: []}
},
data: %Estructura.User.Data{age: -0.0},
name: "y"
}
]