dry2.rb

require 'dry-struct'

module Types
  include Dry::Types.module
end

class Bar < Dry::Struct
  constructor_type :strict_with_defaults
  attribute :baz, Types::Strict::Int
  attribute :bam, Types::Strict::Int.optional.default(nil)
end

describe Bar do
  specify { expect { Bar.new() }.to raise_error }
  specify { expect { Bar.new(baz: 342) }.not_to raise_error }
end