diff --git a/Gemfile b/Gemfile
index 14ef20ad..5a1cae6e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -225,6 +225,8 @@ group :test do
   gem 'timecop'
   # for mocking external requests
   gem 'webmock'
+  # for mocking Stripe responses in tests
+  gem 'stripe-ruby-mock'
 end
 
 group :development, :test do
diff --git a/Gemfile.lock b/Gemfile.lock
index 770dcf66..98196af8 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -141,6 +141,7 @@ GEM
       safe_yaml (~> 1.0.0)
     currencies (0.4.2)
     daemons (1.1.9)
+    dante (0.2.0)
     database_cleaner (1.3.0)
     debug_inspector (0.0.2)
     debugger-linecache (1.2.0)
@@ -483,6 +484,10 @@ GEM
     sqlite3 (1.3.9)
     stripe (1.43.0)
       rest-client (~> 1.4)
+    stripe-ruby-mock (2.3.0)
+      dante (>= 0.2.0)
+      multi_json (>= 1.0.0)
+      stripe (>= 1.31.0, <= 1.43)
     term-ansicolor (1.3.2)
       tins (~> 1.0)
     thor (0.19.1)
@@ -618,6 +623,7 @@ DEPENDENCIES
   spring-commands-rspec
   sqlite3
   stripe
+  stripe-ruby-mock
   timecop
   transitions
   turbolinks
diff --git a/app/models/payment.rb b/app/models/payment.rb
index 4ad4df85..9cab6592 100644
--- a/app/models/payment.rb
+++ b/app/models/payment.rb
@@ -27,6 +27,7 @@ class Payment < ActiveRecord::Base
                                              amount: amount_to_pay,
                                              currency: conference.tickets.first.price_currency
 
+    self.amount = gateway_response[:amount]
     self.last4 = gateway_response[:source][:last4]
     self.authorization_code = gateway_response[:id]
     self.status = 'success'
diff --git a/spec/factories/payments.rb b/spec/factories/payments.rb
index f0829c5c..4d4d3c39 100644
--- a/spec/factories/payments.rb
+++ b/spec/factories/payments.rb
@@ -3,6 +3,5 @@ FactoryGirl.define do
     user
     conference
     status 'unpaid'
-    amount 1000
   end
 end
diff --git a/spec/models/payment_spec.rb b/spec/models/payment_spec.rb
index 4512fe80..1a2be88b 100644
--- a/spec/models/payment_spec.rb
+++ b/spec/models/payment_spec.rb
@@ -1,4 +1,5 @@
 require 'spec_helper'
+require 'stripe_mock'
 
 describe Payment do
 
@@ -32,4 +33,61 @@ describe Payment do
       expect(payment.amount_to_pay).to eq(8000)
     end
   end
+
+  describe '#purchase' do
+    let!(:user) { create(:user) }
+    let!(:conference) { create(:conference) }
+    let!(:ticket_1) { create(:ticket, price: 10, price_currency: 'USD', conference: conference) }
+    let!(:tickets) { {ticket_1.id.to_s => '2'} }
+    let(:stripe_helper) { StripeMock.create_test_helper }
+
+    before { StripeMock.start }
+    after { StripeMock.stop }
+
+    before { TicketPurchase.purchase(conference, user, tickets) }
+    let!(:payment) { create(:payment, user: user, conference: conference, stripe_customer_token: stripe_helper.generate_card_token, stripe_customer_email: user.email) }
+
+    context 'when the payment is successful' do
+      before { payment.purchase }
+
+      it 'assigns amount' do
+        expect(payment.amount).to eq(2000)
+      end
+
+      it 'assigns last4' do
+        expect(payment.last4).to eq('4242')
+      end
+
+      it "assigns 'success' to payment.status" do
+        expect(payment.status).to eq('success')
+      end
+
+      it 'assigns authorization_code' do
+        expect(payment.authorization_code).to eq('test_ch_3')
+      end
+    end
+
+    context 'if the payment is not successful' do
+      before { StripeMock.prepare_card_error(:invalid_number) }
+
+      let(:payment) { create(:payment, user: user, conference: conference, stripe_customer_token: 'bogus_card_token', stripe_customer_email: user.email) }
+
+      before { payment.purchase }
+
+      context 'when the card is invalid' do
+        it 'returns false' do
+          payment_result = payment.purchase
+          expect(payment_result).to eq false
+        end
+
+        it 'assigns "failure" to payment.status' do
+          expect(payment.status).to eq('failure')
+        end
+
+        it 'adds errors' do
+          expect(payment.errors[:base].count).to eq(1)
+        end
+      end
+    end
+  end
 end