Question

我现在正在学习一些Ruby，我决定从在线教程（http://www.sitepoint.com/design-patterns-in-ruby-observer-singleton/）中重新教授一些设计模式。所以我有两个类文件：

汽车

require_relative 'Notifier'
require 'observer'

class Car
include Observable
attr_reader :mileage, :service

def initialize(mileage = 0, service = 3000)
    @mileage, @service = mileage, service
    add_observer(Notifier.new)
end

def log(miles)
    @mileage += miles
    changed
    notify_observers(self, miles)
end
end

通知者：

class Notifier
def update(car, miles)
    puts "The car has logged #{miles} miles, totalling #{car.mileage} miles traveled."
    puts "The car needs to be taken in for a service!" if car.service <= car.mileage
end

端

这是我的测试：

require_relative 'car'
require "test/unit"

class CarTest <
Test::Unit::TestCase

def test_simple
    assert_equal("The car has logged 100 miles, totaling 2400 miles traveled.", Car.new(2300, 3000).log(100))
end

end

但每当我运行测试时，我都会收到此失败消息，想知道是否有人知道为什么会发生这种情况？

[1/1] CarTest#test_simpleThe car has logged 100 miles, totalling 2400 miles traveled.
= 0.00 s
1) Failure:
test_simple(CarTest) [car_test.rb:8]:
<"The car has logged 100 miles, totaling 2400 miles traveled."> expected but was
<false>.

Answer 1

puts打印到stdout。但是您的测试需要Car#log的返回值。这就是它失败的原因。

在同一个说明中，为什么要在Notifier的测试中测试Car的内部结构？

更好的方法是确保观察者得到正确的信息而不关心它的副作用（当然，对于观察者有一个专门的规范，这将测试副作用和诸如此类的东西）

def test_simple
  # sorry, RSpec lingo here, I'm not a minitest guy
  expect_any_instance_of(::Notifier).to receive(:update).with(car, 2400)

  Car.new(2300, 3000).log(100)
end

为什么这个测试失败了？

1 个答案: