validator contract

validator.rb

module Validator
  include Contracts::Core
  class InvalidTypeError < StandardError; end

  Contract Contracts::Num => Contracts::Num
  def self.decimal(value)
    raise InvalidTypeError.new("Not allowed nil type") if value.nil?
    return value if value.is_a?(Integer)
    return value if value.is_a?(BigDecimal)

    value
  end

  Contract ::String => Contracts::Num
  def self.decimal(value)
    return BigDecimal.new(value)
  rescue ArgumentError => e
    raise InvalidTypeError.new("Invalid string for decimal conversion")
  end
end

validator_test.rb

require 'test_helper'

class ValidatorTest < ActiveSupport::TestCase
  test ".decimal validate decimal" do
    assert_equal 1.7.to_d, Validator.decimal(1.7)
  end

  test ".decimal validate integer" do
    assert_equal 1.to_d, Validator.decimal(1)
  end

  test ".decimal validate valid string" do
    assert_equal 1.7.to_d, Validator.decimal("1.7")
  end

  test ".decimal exception for nil" do
    err = assert_raises(ContractError) { Validator.decimal(nil) }
    assert_match(/Expected: String,\n\s+Actual: nil\n/, err.message)
  end

  test ".decimal exception invalid string" do
    err = assert_raises(Validator::InvalidTypeError) { Validator.decimal("a") }
    assert_match(/Invalid string for decimal conversion/, err.message)
  end
end