Use Estonian reference number format instead of ISO 11649

test/models/billing/reference_no/base_test.rb

@@ -0,0 +1,29 @@
+require 'test_helper'
+
+# https://www.pangaliit.ee/settlements-and-standards/reference-number-of-the-invoice
+class ReferenceNoBaseTest < ActiveSupport::TestCase
+  def test_generates_random_base
+    assert_not_equal Billing::ReferenceNo::Base.generate, Billing::ReferenceNo::Base.generate
+  end
+
+  def test_randomly_generated_base_conforms_to_standard
+    base = Billing::ReferenceNo::Base.generate
+    format = /\A\d{1,19}\z/
+    assert_match format, base.to_s
+  end
+
+  def test_generates_check_digit_for_a_given_base
+    assert_equal 3, Billing::ReferenceNo::Base.new('1').check_digit
+    assert_equal 7, Billing::ReferenceNo::Base.new('1234567891234567891').check_digit
+  end
+
+  def test_returns_string_representation
+    base = Billing::ReferenceNo::Base.new('1')
+    assert_equal '1', base.to_s
+  end
+
+  def test_normalizes_non_string_values
+    base = Billing::ReferenceNo::Base.new(1)
+    assert_equal '1', base.to_s
+  end
+end