Convert specs to tests

test/fixtures/bank_statements.yml

@@ -0,0 +1,3 @@
+one:
+  bank_code: '1234'
+  iban: GB33BUKB20201555555555

test/models/bank_statement_test.rb

@@ -0,0 +1,25 @@
+require 'test_helper'
+
+class BankStatementTest < ActiveSupport::TestCase
+  def test_valid_bank_statement_fixture_is_valid
+    assert valid_bank_statement.valid?, proc { valid_bank_statement.errors.full_messages }
+  end
+
+  def test_invalid_without_bank_code
+    bank_statement = valid_bank_statement
+    bank_statement.bank_code = ''
+    assert bank_statement.invalid?
+  end
+
+  def test_invalid_without_iban
+    bank_statement = valid_bank_statement
+    bank_statement.iban = ''
+    assert bank_statement.invalid?
+  end
+
+  private
+
+  def valid_bank_statement
+    bank_statements(:one)
+  end
+end