Update VAT

#623

test/models/invoice_test.rb

@@ -1,9 +1,34 @@
 require 'test_helper'
 
 class InvoiceTest < ActiveSupport::TestCase
+  def setup
+    @invoice = invoices(:valid)
+  end
+
+  def test_valid
+    assert @invoice.valid?
+  end
+
   def test_invalid_without_vat_rate
-    invoice = Invoice.new(vat_rate: nil)
-    invoice.validate
-    assert invoice.errors.added?(:vat_rate, :blank)
+    @invoice.vat_rate = nil
+    assert @invoice.invalid?
+  end
+
+  def test_allows_absent_vat_rate
+    @invoice.vat_rate = nil
+    @invoice.validate
+    assert @invoice.valid?
+  end
+
+  def test_rejects_negative_vat_rate
+    @invoice.vat_rate = -1
+    @invoice.validate
+    assert @invoice.invalid?
+  end
+
+  def test_rejects_vat_rate_greater_than_max
+    @invoice.vat_rate = 100
+    @invoice.validate
+    assert @invoice.invalid?
   end
 end