diff --git a/app/models/concerns/model/jbuilder.rb b/app/models/concerns/model/jbuilder.rb
index c468018b..f4584c47 100644
--- a/app/models/concerns/model/jbuilder.rb
+++ b/app/models/concerns/model/jbuilder.rb
@@ -5,15 +5,98 @@
 module Model::Jbuilder
 	extend ActiveSupport::Concern
 	class_methods do
-		def add_builder_expansion(*args, **kwargs)
-			builder_expansions.add_builder_expansion(*args, **kwargs)
+		#
+		# Builder expansions address a common issue when using Jbuilder for generated JSON for object events work with `#init_builder`
+		# In some situations, a model may reference another object but, depending on the situation, may not want to expand that object
+		# 
+		# As an example, consider an hypothetical Supporter class with a reference to a Nonprofit
+		#
+		# class Supporter < ApplicationRecord
+		#		belongs_to :nonprofit
+		#   belongs_to :group
+		# 	def to_builder(*expand)
+		#			 init_builder(*expand) do 
+		#      # build you JBuilder object
+		#			 end
+		#   end
+		# end
+		#
+		# When generating the the Jbuilder object, you may want to expand the nonprofit object or in other situations not expand it. To handle this
+		# you would need to write the following code:
+		# `
+		#	if expand.include? :nonprofit
+		#		json.nonprofit nonprofit.to_builder.attributes!
+		#	else
+		#		json.nonprofit nonprofit.to_id
+		#	end
+		#  `
+		# You would have to write the same code for `group`. As your number of expandable attributes increase, your code gets filled with boilerplate code.
+		# 
+		# `add_builder_expansion` addresses this by autocreating this code in to_builder.
+		# For example, if you want nonprofit to be expandable as in the nonprofit json attribute, and group into the group json attribute. You only need to write:
+		# `add_builder_expansion :nonprofit, :group`
+		# You can put as many expandable attributes there as you'd like.
+		#
+		# On the other hand, let's say you want to make group expandable BUT you want to assign it to the "supporter_group" json attribute. To do that, you
+		# pass in the attribute you want to be expandable along with the "json_attribute" method key set to 'supporter_group': 
+		# `add_builder_expansion :group, json_attribute: 'supporter_group'`
+		#
+		# For enumerable attributes (like a has_many or an array), there are two ways you may want to include them into your json output. If it's a set of simple values 
+		# like, an array of strings or numbers, you may want to want to the array output as-is. For example, let's say you have a array of tags which are strings. You may want
+		# it to be output like so:
+		# ````
+		# tags: [ 'founders circle', 'large donor']
+		# ```
+		# We call these `:flat` enumerable attribtes. Assuming the supporter class before has a tags attribute, you would add the tags builder_expansion using:
+		# ```
+		# add_builder_expansion :tags, enum_type: :flat
+		# ```
+		#
+		# On the other hand, you may want to have an array of other Jbuilder created objects. Let's say your supporter has many groups. You may want these attributes expanded in
+		# one of two ways: expanded or unexpanded.
+		# 
+		# For expanded, you would receive have something like this in your output:
+		# 
+		# {
+		#		# ... some other parts of the supporter json
+		# 	groups: [{ id: 546, name: 'group name 1'}, {id: 235, name: 'group name 2'}]
+		# }
+		# 
+		# However, for unexpanded, you'd just want the ids:
+		# 
+		# {
+		#		# ... some other parts of the supporter json
+		# 	groups: [546, 235]
+		# }
+		#
+		# For this type of builder expansion, you would use:
+		# ```
+		# add_builder expansion :groups, enum_type: :expandable
+		# ```
+		#
+		# @param [Symbol] *attributes the attributes you'd like to make expandable. If you want to set options, there should only be a single attribute here.
+		# @param  **options options for configuring the builder expansion. The options right now are:
+		# - `json_attribute`: the json attribute name in the outputted Jbuilder. Defaults to the attribute name.
+		# - `enum_type`: the type of enumerable for the attribute. pass :flat if the enumerable attribute is flat, or :expandable if it's expandable. ANy other value 
+		# including the default of nil, means the attribute is not enumerable.
+		#
+		def add_builder_expansion(*attributes, **options)
+			builder_expansions.add_builder_expansion(*attributes, **options)
 		end
 
-		def builder_expansions
+		#
+		# A set of all the builder expansions configured for a class
+		#
+		# @return [Array] the builder expansions
+		#
+		def builder_expansions 
 			@builder_expansions ||= BuilderExpansionSet.new
 		end
 	end
 
+	def to_id
+		id
+	end
 
 	class BuilderExpansionSet < Set
 		def add_builder_expansion(*args, **kwargs)
@@ -44,37 +127,59 @@ module Model::Jbuilder
 
 	class BuilderExpansion
 		include ActiveModel::AttributeAssignment
-		attr_accessor :key, :json_attrib, :to_id,
-			:to_expand, :if, :unless, :on_else, :to_attrib
+		attr_accessor :key, :json_attribute, :enum_type
 
 		def initialize(new_attributes)
 			assign_attributes(new_attributes)
 		end
+		def enumerable?
+			expandable_enum? || flat_enum?
+		end
 
-		def json_attrib
-			@json_attrib || key
+		def expandable_enum?
+			enum_type == :expandable
+		end
+
+		def flat_enum?
+			enum_type == :flat
+		end
+
+		def json_attribute
+			(@json_attribute || key).to_s
 		end
 
 		def to_id
-			if @to_id
-				return @to_id
-			elsif @to_attrib
-				return -> (model, be=self) { to_attrib.(model).id }
-			else
-				return ->(model,be=self) { model.send(be.key).id}
-			end
+			return ->(model,be=self) {	
+				value = be.get_attribute_value model
+				if be.expandable_enum?
+					value&.map{|i| i&.to_id}
+				elsif be.flat_enum?
+					value
+				else
+					value&.to_id	
+				end
+			}	
 		end
 
-		def to_expand
-			if @to_expand
-				return @to_expand
-			elsif @to_attrib
-				return -> (model, be=self) {	to_attrib.(model).to_builder }
-			else
-				return ->(model,be=self) { model.send(be.key).to_builder}
-			end
+		def to_builder
+			return ->(model,be=self) { 
+				value = be.get_attribute_value model
+				if be.expandable_enum?
+					value&.map{|i| i&.to_builder}
+				elsif be.flat_enum?
+					value
+				else
+					value&.to_builder
+				end
+			}
+		end
 
-			
+		def get_attribute_value(model)
+			if model.respond_to? key
+				model.send(key)
+			else
+				raise ActiveModel::MissingAttributeError, "missing attribute: #{key}"
+			end
 		end
 	end
 
@@ -86,9 +191,9 @@ module Model::Jbuilder
 			json.object self.class.name.underscore
 			builder_expansions.keys.each do |k|
 				if expand.include? k
-					json.set! builder_expansions.get_by_key(k).json_attrib, builder_expansions.get_by_key(k).to_expand.(self)
+					json.set! builder_expansions.get_by_key(k).json_attribute, builder_expansions.get_by_key(k).to_builder.(self)
 				else
-					json.set! builder_expansions.get_by_key(k).json_attrib, builder_expansions.get_by_key(k).to_id.(self)
+					json.set! builder_expansions.get_by_key(k).json_attribute, builder_expansions.get_by_key(k).to_id.(self)
 				end
 			end
 			yield(json)
diff --git a/app/models/concerns/model/trx_assignable.rb b/app/models/concerns/model/trx_assignable.rb
index 4e4761c6..ba6dd3c3 100644
--- a/app/models/concerns/model/trx_assignable.rb
+++ b/app/models/concerns/model/trx_assignable.rb
@@ -13,7 +13,7 @@ module Model::TrxAssignable
 		add_builder_expansion :nonprofit, :supporter
 
 		add_builder_expansion :trx, 
-			json_attrib: :transaction
+			json_attribute: :transaction
 
 		has_one :transaction_assignment, as: :assignable
 		has_one :trx, through: :transaction_assignment
diff --git a/app/models/modern_campaign_gift.rb b/app/models/modern_campaign_gift.rb
index 5c78b808..a2d7a194 100644
--- a/app/models/modern_campaign_gift.rb
+++ b/app/models/modern_campaign_gift.rb
@@ -10,7 +10,7 @@ class ModernCampaignGift < ApplicationRecord
 	
 	add_builder_expansion :nonprofit, :supporter, :campaign, :campaign_gift_option, :campaign_gift_purchase
   add_builder_expansion :trx, 
-		json_attrib: :transaction
+		json_attribute: :transaction
 
 	belongs_to :campaign_gift_purchase
 	belongs_to :legacy_campaign_gift,  class_name: 'CampaignGift', foreign_key: :campaign_gift_id, inverse_of: :modern_campaign_gift
diff --git a/app/models/supporter_note.rb b/app/models/supporter_note.rb
index 6bbfaf51..a955f7b2 100644
--- a/app/models/supporter_note.rb
+++ b/app/models/supporter_note.rb
@@ -18,10 +18,7 @@ class SupporterNote < ApplicationRecord
   validates :supporter_id, presence: true
   # TODO replace with Discard gem
 
-  add_builder_expansion :supporter, :nonprofit
-  add_builder_expansion :user, 
-    to_id: ->(model) { model.user&.id},
-    to_expand: ->(model) { model.user&.to_builder}
+  add_builder_expansion :supporter, :nonprofit, :user
 
   define_model_callbacks :discard
 
diff --git a/app/models/ticket_purchase.rb b/app/models/ticket_purchase.rb
index ed9df611..cf2dae7a 100644
--- a/app/models/ticket_purchase.rb
+++ b/app/models/ticket_purchase.rb
@@ -6,11 +6,8 @@ class TicketPurchase < ApplicationRecord
   include Model::TrxAssignable
   setup_houid :tktpur
 
-  add_builder_expansion :event
+  add_builder_expansion :event, :event_discount
   
-  add_builder_expansion :event_discount,
-    to_id: -> (model) { model.event_discount&.id },
-    to_expand: -> (model) { model.event_discount&.to_builder }
   
   before_create :set_original_discount
 
diff --git a/app/models/ticket_to_legacy_ticket.rb b/app/models/ticket_to_legacy_ticket.rb
index ad65d438..c8cb8f0d 100644
--- a/app/models/ticket_to_legacy_ticket.rb
+++ b/app/models/ticket_to_legacy_ticket.rb
@@ -21,11 +21,7 @@ class TicketToLegacyTicket < ApplicationRecord
   
   setup_houid :tkt
 
-  add_builder_expansion :ticket_purchase, :ticket_level, :supporter, :event, :nonprofit
-
-  add_builder_expansion :event_discount,
-    to_id: -> (model) { model.event_discount&.id},
-    to_expand: -> (model) { model.event_discount&.to_builder}
+  add_builder_expansion :ticket_purchase, :ticket_level, :supporter, :event, :nonprofit, :event_discount
 
   def to_builder(*expand)
     init_builder(*expand) do |json|
diff --git a/spec/models/concerns/model/jbuilder_spec.rb b/spec/models/concerns/model/jbuilder_spec.rb
new file mode 100644
index 00000000..c5f4bb26
--- /dev/null
+++ b/spec/models/concerns/model/jbuilder_spec.rb
@@ -0,0 +1,150 @@
+# frozen_string_literal: true
+
+# License: AGPL-3.0-or-later WITH WTO-AP-3.0-or-later
+# Full license explanation at https://github.com/houdiniproject/houdini/blob/master/LICENSE
+require 'rails_helper'
+
+RSpec.describe Model::Jbuilder do
+	describe Model::Jbuilder::BuilderExpansion do
+		let(:model) do
+			stub_const('HasToBuilderAndToId', Struct.new(:to_id, :to_builder))
+
+			stub_const('ModelClass', Struct.new(:filled, :unfilled, :enumerable))
+
+			ModelClass.new(
+				HasToBuilderAndToId.new('id_result', 'builder_result'),
+				nil,
+				[
+					HasToBuilderAndToId.new('enumerable_id_result_1', 'enumerable_builder_result_1'),
+					HasToBuilderAndToId.new('enumerable_id_result_2', 'enumerable_builder_result_2')
+				]
+			)
+		end
+		let(:filled_expansion) { described_class.new(key: :filled, json_attribute: 'filled_attrib') }
+		let(:unfilled_expansion) { described_class.new(key: :unfilled) }
+		let(:nonexistent_expansion) { described_class.new(key: :nonexistent) }
+		let(:expandable_expansion) { described_class.new(key: :enumerable, enum_type: :expandable) }
+		let(:flat_expansion) { described_class.new(key: :enumerable, enum_type: :flat) }
+
+		describe 'expansion where the attribute is filled' do
+			subject { filled_expansion }
+
+			it {
+				is_expected.to have_attributes(
+					json_attribute: 'filled_attrib',
+					enumerable?: false,
+					flat_enum?: false,
+					expandable_enum?: false
+				)
+			}
+
+			describe '#to_id' do
+				subject { filled_expansion.to_id.call(model) }
+
+				it { is_expected.to eq 'id_result' }
+			end
+
+			describe '#to_builder' do
+				subject { filled_expansion.to_builder.call(model) }
+
+				it { is_expected.to eq 'builder_result' }
+			end
+		end
+
+		describe 'expansion where the attribute is unfilled' do
+			subject { unfilled_expansion }
+
+			it {
+				is_expected.to have_attributes(
+					json_attribute: 'unfilled',
+					enumerable?: false,
+					flat_enum?: false,
+					expandable_enum?: false
+				)
+			}
+
+			describe '#to_id' do
+				subject { unfilled_expansion.to_id.call(model) }
+
+				it { is_expected.to eq nil }
+			end
+
+			describe '#to_builder' do
+				subject { unfilled_expansion.to_builder.call(model) }
+
+				it { is_expected.to eq nil }
+			end
+		end
+
+		describe 'expansion where the attribute is nonexistent' do
+			subject { nonexistent_expansion }
+
+			it {
+				is_expected.to have_attributes(
+					json_attribute: 'nonexistent',
+					enumerable?: false,
+					flat_enum?: false,
+					expandable_enum?: false
+				)
+			}
+
+			it '.to_id raises error' do
+				expect { nonexistent_expansion.to_id.call(model) }.to raise_error ActiveModel::MissingAttributeError
+			end
+
+			it '.to_builder raises error' do
+				expect { nonexistent_expansion.to_builder.call(model) }.to raise_error ActiveModel::MissingAttributeError
+			end
+		end
+
+		describe 'expansion of expandable enumerable returns an enumerable' do
+			subject { expandable_expansion }
+
+			it {
+				is_expected.to have_attributes(
+					json_attribute: 'enumerable',
+					enumerable?: true,
+					flat_enum?: false,
+					expandable_enum?: true
+				)
+			}
+
+			describe '#to_id' do
+				subject { expandable_expansion.to_id.call(model) }
+
+				it { is_expected.to match(%w[enumerable_id_result_1 enumerable_id_result_2]) }
+			end
+
+			describe '#to_builder' do
+				subject { expandable_expansion.to_builder.call(model) }
+
+				it { is_expected.to match(%w[enumerable_builder_result_1 enumerable_builder_result_2]) }
+			end
+		end
+
+		describe 'expansion of flat enumerable returns an enumerable' do
+			subject { flat_expansion }
+
+			it {
+				is_expected.to have_attributes(
+					json_attribute: 'enumerable',
+					enumerable?: true,
+					flat_enum?: true,
+					expandable_enum?: false
+				)
+			}
+
+			describe '#to_id' do
+				subject { expandable_expansion.to_id.call(model) }
+
+				it { is_expected.to match(%w[enumerable_id_result_1 enumerable_id_result_2]) }
+			end
+
+			describe '#to_builder' do
+				subject { expandable_expansion.to_builder.call(model) }
+
+				it { is_expected.to match(%w[enumerable_builder_result_1 enumerable_builder_result_2]) }
+			end
+		end
+	end
+end
diff --git a/spec/models/transaction_spec.rb b/spec/models/transaction_spec.rb
index 3e4590e7..b8fe5b34 100644
--- a/spec/models/transaction_spec.rb
+++ b/spec/models/transaction_spec.rb
@@ -10,7 +10,7 @@ RSpec.describe Transaction, type: :model do
   describe 'to_builder' do 
     subject { supporter.transactions.create(amount: 1000).to_builder.attributes!}
     it 'will create a proper builder result' do 
-      expect(subject).to match({
+      is_expected.to match({
         'id' => match('trx_[a-zA-Z0-9]{22}'),
         'nonprofit' => nonprofit.id,
         'supporter' => supporter.id,