如何设置在方法测试中使用的私有实例变量？ [英] How to set private instance variable used within a method test?

问题描述

给出一个带有几个实例变量和一些方法的类。可以通过 attr_reader 和 attr_accessor 设置一些实例变量的访问权限。

一些私有实例变量在一个实例方法中设置并在另一个方法中读取/利用。

Given a class with a couple of instance variables and some methods. Some instance variables are set accessible via attr_reader and attr_accessor. Thus the others are private.
Some of the private instance variables get set within one of the instance methods and read/utilized within another method.

为了进行测试，我使用了RSpec。由于我还是Ruby的新手，并且想让所有事情都做对，因此我定义了相当精细的测试。因此，对于每个实例方法，我都有一个 describe 块，它们本身被划分为 context s的子集， it s。一般环境先决条件用 before 定义。

For testing I'm using RSpec. As I'm still new to Ruby and want to get all things right, I defined my tests being rather fine-grained. Thus I've got one describe block for each instance method, which themselves are partitioned into a subset of contexts and its. General environmental preconditions are defined with before.

但是，当测试其中一种方法时，该方法正在使用但未使用设置一个私有变量，我需要调用另一个方法，即设置此变量。对我来说，这似乎超重了，而且不是模块化的。

However, when testing one of the methods, which is utilizing but not setting one of the private variables, I need to call the other method, which is setting this variable. This seems rather overweight and not modular for me.

有没有一种方法可以将私有实例变量强制为某个值。类似于 提取，使用 Object :: instance_eval（：var）的私有实例变量的值。

Is there a way of forcing a private instance variable to a certain value. Similar to "ripping out" the value of a private instance variable with Object::instance_eval(:var).

推荐答案

在回答问题时，设置实例变量的最简单方法是使用 instance_eval 方法：

As you answered in your question the easiest way to set instance variable is with instance_eval method:

obj.instance_eval('@a = 1')

另一种方法是使用instance_variable_set：

Another way is to use instance_variable_set:

obj.instance_variable_set(:@a, 1)

但是我不建议您这样做。规范全部涉及测试对象的行为以及通过使用 instance_eval 破坏类封装来测试行为，这将使您的测试更加脆弱且依赖于实现。

But I would not recommend to do this in your specs. Specs are all about testing behavior of an object and testing behaviour by breaking class encapsulation with instance_eval will make your tests more fragile and implementation dependent.

对象状态隔离的另一种方法是存根访问器方法：

Alternative approach to object state isolation is to stub accessor methods:

class UnderTest
  attr_accessor :a

  def test_this
    do_something if a == 1
  end
end

#in your test
under_test = UnderTest.new
under_test.stub(:a).and_return(1)

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