Output

Stevens-MacBook-Air:invoicing_app srbaker$ maglev-ruby test_invoice.rb 
Run options: --seed 18641

# Running tests:

during at_exit handler 1: error , a ArgumentError occurred (error 2718), too few arguments
Stevens-MacBook-Air:invoicing_app srbaker$ 

test_invoice.rb

require 'minitest/autorun'

class TestInvoice < MiniTest::Unit::TestCase
  def test_new_invoice
    invoice = Invoice.new Money.new(12345), '123456789', '98765'

    assert_equal Money.new(12345), invoice.amount
    assert_equal '123456789', invoice.number
    assert_equal '98765', invoice.customer_number
  end
end