ruby - Rspec it{} 评估使用最后一个变量值

Question

我正在使用 Rspec 为我的程序做一些测试。在规范中，我将类实例化一次，并使用describes 和contexts 对其执行测试。我遇到了一些有趣的事情，如果 its 似乎在上下文的末尾被评估。例如，给定以下类及其相关规范:

class Tmp
  def initialize
    @values = {}
  end

  def modify(new_value1, new_value2)
    @values = {:a => new_value1, :b => new_value2}
  end

  def get_values
    return @values
  end
end

---

describe Tmp do
  tmp = Tmp.new()

  describe "testing something" do
    context "change value" do

      # First evaluation
      tmp.modify("hi", "bye")
      it {tmp.get_values.should == {:a => "hi", :b => "bye"}}

      # Second evaluation
      tmp.modify("bye", "hi")
      it {tmp.get_values.should == {:a => "bye", :b => "hi"}}
    end
  end
end

---

使用提供的类和规范，结果如下:

F.

Failures:

  1) Tmp testing something change value 
     Failure/Error: it {tmp.get_values.should == {:a => "hi", :b => "bye"}}
       expected: {:a=>"hi", :b=>"bye"}
            got: {:a=>"bye", :b=>"hi"} (using ==)
       Diff:
       @@ -1,3 +1,3 @@
       -:a => "hi",
       -:b => "bye"
       +:a => "bye",
       +:b => "hi"
     # ./spec/tmp_spec.rb:11:in `block (4 levels) in <top (required)>'

Finished in 0.00211 seconds
2 examples, 1 failure

这很有趣，因为 Rspec 似乎使用 tmp 中的值评估第一个 it，因为它位于上下文的末尾。即使在上下文中 tmp 正在改变它的值并且应该通过，Rspec 也会根据变量在结束(我什至在 context 中用局部原始变量尝试过这个并且有类似的经历)。

有没有办法解决这个问题并按顺序评估its？或者至少让以下测试通过？我知道我可以使用不同的变量并且它会起作用，但必须有办法解决这个问题。我还想知道这是否是 Rspec 的预期效果。

更新菲利普的回答

通过在单个 it block 中进行更改，规范通过:

describe Tmp do
  describe "do something" do
    let(:instance) {Tmp.new}

    it 'should be modifiable' do
      instance.modify('hi', 'bye')
      instance.values.should == {a: 'hi', b: 'bye'}
      instance.modify('bye', 'hi')
      instance.values.should == {a: 'bye', b: 'hi'}
    end
  end
end

但如果我使用主题，它似乎会返回并在第一个应该上失败

describe Tmp do
  describe "do something" do
    let(:instance) {Tmp.new}
    subject{instance.values}

    it 'should be modifiable' do
      instance.modify('hi', 'bye')
      should == {a: 'hi', b: 'bye'}
      instance.modify('bye', 'hi')
      should == {a: 'bye', b: 'hi'}
    end
  end
end

不知道为什么会这样。至少我看到更改应该在 it block 中以更好地反射(reflect)我们正在测试的更改。

Answer 1

您不应该在 it、specify、before、let 之外创建实例和操作它们和 subject block 。否则主题和其他变量不会在测试后重置。

下面我使用几种不同的样式重写了您的规范。请参阅内联注释以获取解释。

class Tmp
  # Exposes the @values ivar through #values
  attr_reader :values

  def initialize
    @values = {}
  end

  def modify(new_value1, new_value2)
    @values = {a: new_value1, b: new_value2}
  end
end

describe Tmp do
  #`let` makes the return value of the block available as a variable named `instance` (technically it is a method named instance, but let's call it a variable).
  let(:instance) { described_class.new }

  # Inside an it block you can access the variables defined through let.
  it 'should be modifiable' do
    instance.modify('hi', 'bye')
    instance.values.should == {a: 'hi', b: 'bye'}
  end

  # or

  # `specify` is like `it` but it takes no argument:
  specify do
    instance.modify('hi', 'bye')
    instance.values.should == {a: 'hi', b: 'bye'}
  end

  # or

  # This is another common way of defining specs, one describe per method.
  describe '#modify' do
    let(:instance) { described_class.new }
    # Here we define the subject which is used implicitly when calling `#should` directly.
    subject { instance.values }
    before { instance.modify('hi', 'bye') }
    it { should == {a: 'hi', b: 'bye' } # Equivalent to calling `subject.should == ...`
  end

  # or

  # When we don't specify a subject, it will be an instance of the top level described object (Tmp).
  describe '#modify' do
    before { subject.modify('hi', 'bye') }
    its(:values) { should == {a: 'hi', b: 'bye' }
  end
end