diff --git a/app/models/expense.rb b/app/models/expense.rb
index 32f486f..6da98af 100644
--- a/app/models/expense.rb
+++ b/app/models/expense.rb
@@ -12,4 +12,11 @@
 #  updated_at   :datetime         not null
 #
 class Expense < ApplicationRecord
+  enum :pricing_type,
+       fixed: 'fixed',
+       per_person: 'per_person'
+
+  validates :name, presence: true
+  validates :amount, presence: true, numericality: { greater_than: 0 }
+  validates :pricing_type, presence: true
 end
diff --git a/spec/models/expense_spec.rb b/spec/models/expense_spec.rb
index a6592fe..973ccf2 100644
--- a/spec/models/expense_spec.rb
+++ b/spec/models/expense_spec.rb
@@ -3,5 +3,10 @@
 require 'rails_helper'
 
 RSpec.describe Expense, type: :model do
-  pending "add some examples to (or delete) #{__FILE__}"
+  describe 'validations' do
+    it { should validate_presence_of(:name) }
+    it { should validate_presence_of(:amount) }
+    it { should validate_numericality_of(:amount).is_greater_than(0) }
+    it { should validate_presence_of(:pricing_type) }
+  end
 end
diff --git a/spec/requests/expenses_spec.rb b/spec/requests/expenses_spec.rb
new file mode 100644
index 0000000..c96b5cf
--- /dev/null
+++ b/spec/requests/expenses_spec.rb
@@ -0,0 +1,49 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+require 'swagger_helper'
+
+RSpec.describe 'expenses', type: :request do
+  path '/expenses' do
+    get('list expenses') do
+      tags 'Expenses'
+      produces 'application/json'
+      response(200, 'successful') do
+        schema type: :array,
+               items: {
+                 type: :object,
+                 required: %i[id name amount pricing_type],
+                 properties: {
+                   id: { type: :string, format: :uuid },
+                   name: { type: :string },
+                   amount: { type: :number },
+                   pricing_type: { type: :string, enum: Expense.pricing_types.keys }
+                 }
+               }
+
+        xit
+      end
+    end
+  end
+
+  path '/expenses/{id}' do
+
+    patch('update expense') do
+      tags 'Expenses'
+      consumes 'application/json'
+      produces 'application/json'
+      parameter name: 'id', in: :path, type: :string, format: :uuid, description: 'id'
+      parameter name: :body, in: :body, schema: {
+        type: :object,
+        properties: {
+          name: { type: :string },
+          amount: { type: :number, minimum: 0 },
+          pricing_type: { type: :string, enum: Expense.pricing_types.keys }
+        }
+      }
+
+      response_empty_200
+      response_422
+      response_404
+    end
+  end
+end
diff --git a/spec/requests/guests_spec.rb b/spec/requests/guests_spec.rb
index fedbce1..9a92de9 100644
--- a/spec/requests/guests_spec.rb
+++ b/spec/requests/guests_spec.rb
@@ -22,14 +22,7 @@ RSpec.describe 'guests', type: :request do
           }
         }
       }
-      let(:body) do
-        {
-          guest_ids: [SecureRandom.uuid, SecureRandom.uuid],
-          properties: {
-            status: 'confirmed'
-          }
-        }
-      end
+
       response_empty_200
       response_422
     end