Add EveryPay payments

* Refactor BankLink into Payments::BankLink, add Payments::EveryPay
* Write tests for existing invoice views
* Write basic tests for Payments module

test/models/payments_test.rb

@@ -0,0 +1,58 @@
+require 'test_helper'
+
+class PaymentTest < ActiveSupport::TestCase
+  def setup
+    super
+
+    @original_methods = ENV['payment_methods']
+    @original_seb_URL = ENV['seb_payment_url']
+    ENV['payment_methods'] = 'seb, swed, credit_card'
+    ENV['seb_payment_url'] = nil
+    @not_implemented_payment = Payments::Base.new(
+      'not_implemented', Invoice.new
+    )
+  end
+
+  def teardown
+    super
+
+    ENV['payment_methods'] = @original_methods
+    ENV['seb_payment_url'] = @original_seb_URL
+  end
+
+  def test_variable_assignment
+    assert_equal 'not_implemented', @not_implemented_payment.type
+    assert_nil @not_implemented_payment.response_url
+    assert_nil @not_implemented_payment.return_url
+    assert_nil @not_implemented_payment.form_url
+  end
+
+  def test_that_errors_are_raised_on_not_implemented_methods
+    assert_raise NotImplementedError do
+      @not_implemented_payment.valid_response?
+    end
+
+    assert_raise NotImplementedError do
+      @not_implemented_payment.settled_payment?
+    end
+
+    assert_raise NotImplementedError do
+      @not_implemented_payment.form_fields
+    end
+
+    assert_raise NotImplementedError do
+      @not_implemented_payment.complete_transaction
+    end
+  end
+
+  def test_that_create_with_type_raises_argument_error
+    assert_raise ArgumentError do
+      Payments.create_with_type("not_implemented", Invoice.new)
+    end
+  end
+
+  def test_create_with_correct_subclass
+    payment = Payments.create_with_type('seb', Invoice.new)
+    assert_equal Payments::BankLink, payment.class
+  end
+end