模块：RSpec::Core::MemoizedHelpers::ClassMethods

包含于
ExampleGroup
定义于
lib/rspec/core/memoized_helpers.rb

概述

此模块扩展到 ExampleGroup，使这些方法可以在示例组块中调用。您可以将其视为类似于类宏。

实例方法摘要 折叠

实例方法详细信息

#let(name, &block) ⇒void

注意

let 可以在任何给定的示例组中适度使用（1、2 或可能 3 个声明）时提高可读性，但过度使用会导致可读性迅速下降。YMMV。

注意

let 可以配置为线程安全或不安全。如果它是线程安全的，访问该值的时间会更长。如果它不是线程安全的，它可能会在生成单独线程的示例中以令人惊讶的方式表现。在 RSpec.configure 上指定此选项。

注意

因为 let 旨在创建在每个示例之间重置的状态，而 before(:context) 旨在设置在示例组中的所有示例之间共享的状态，所以 let 不打算在 before(:context) 钩子中使用。

生成一个方法，该方法的返回值在第一次调用后被记忆。这对于减少在示例之间分配相同局部变量的值的重复很有用。

示例


RSpec.describe Thing do
  let(:thing) { Thing.new }
  it "does something" do
    # First invocation, executes block, memoizes and returns result.
    thing.do_something
    # Second invocation, returns the memoized value.
    thing.should be_something
  end
end
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# File 'lib/rspec/core/memoized_helpers.rb', line 306
def let(name, &block)
  # We have to pass the block directly to `define_method` to
  # allow it to use method constructs like `super` and `return`.
  raise "#let or #subject called without a block" if block.nil?
  # A list of reserved words that can't be used as a name for a memoized helper
  # Matches for both symbols and passed strings
  if [:initialize, :to_s].include?(name.to_sym)
    raise ArgumentError, "#let or #subject called with reserved name `#{name}`"
  end
  our_module = MemoizedHelpers.module_for(self)
  # If we have a module clash in our helper module
  # then we need to remove it to prevent a warning.
  #
  # Note we do not check ancestor modules (see: `instance_methods(false)`)
  # as we can override them.
  if our_module.instance_methods(false).include?(name)
    our_module.__send__(:remove_method, name)
  end
  our_module.__send__(:define_method, name, &block)
  # If we have a module clash in the example module
  # then we need to remove it to prevent a warning.
  #
  # Note we do not check ancestor modules (see: `instance_methods(false)`)
  # as we can override them.
  if instance_methods(false).include?(name)
    remove_method(name)
  end
  # Apply the memoization. The method has been defined in an ancestor
  # module so we can use `super` here to get the value.
  if block.arity == 1
    define_method(name) { __memoized.fetch_or_store(name) { super(RSpec.current_example, &nil) } }
  else
    define_method(name) { __memoized.fetch_or_store(name) { super(&nil) } }
  end
end

#let!(name, &block) ⇒void

与 let 相同，只是块由一个隐式的 before 钩子调用。这具有设置状态和提供对该状态的记忆引用的双重目的。

示例


class Thing
  def self.count
    @count ||= 0
  end
  def self.count=(val)
    @count += val
  end
  def self.reset_count
    @count = 0
  end
  def initialize
    self.class.count += 1
  end
end
RSpec.describe Thing do
  after(:example) { Thing.reset_count }
  context "using let" do
    let(:thing) { Thing.new }
    it "is not invoked implicitly" do
      Thing.count.should eq(0)
    end
    it "can be invoked explicitly" do
      thing
      Thing.count.should eq(1)
    end
  end
  context "using let!" do
    let!(:thing) { Thing.new }
    it "is invoked implicitly" do
      Thing.count.should eq(1)
    end
    it "returns memoized version on first invocation" do
      thing
      Thing.count.should eq(1)
    end
  end
end
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# File 'lib/rspec/core/memoized_helpers.rb', line 400
def let!(name, &block)
  let(name, &block)
  before { __send__(name) }
end

#subject(name = nil, &block) ⇒void

注意

subject 可以配置为线程安全或不安全。如果它是线程安全的，访问该值的时间会更长。如果它不是线程安全的，它可能会在生成单独线程的示例中以令人惊讶的方式表现。在 RSpec.configure 上指定此选项。

为一个示例组声明一个 subject，然后可以使用 expect 和 is_expected 包裹它，使其成为在一个简洁的单行示例中进行期望的目标。

给定一个 name，定义一个具有该名称的方法，该方法返回 subject。这允许您声明一次主题，并在单行代码中隐式地访问它，以及使用揭示意图的名称显式地访问它。

当给定一个 name 时，在块中调用 super 不受支持。

示例


RSpec.describe CheckingAccount, "with $50" do
  subject { CheckingAccount.new(Money.new(50, :USD)) }
  it { is_expected.to have_a_balance_of(Money.new(50, :USD)) }
  it { is_expected.not_to be_overdrawn }
end
RSpec.describe CheckingAccount, "with a non-zero starting balance" do
  subject(:account) { CheckingAccount.new(Money.new(50, :USD)) }
  it { is_expected.not_to be_overdrawn }
  it "has a balance equal to the starting balance" do
    .balance.should eq(Money.new(50, :USD))
  end
end

参数

  • name (String, Symbol) (默认值为: nil) —

    用于定义一个具有揭示意图的名称的访问器

  • block —

    定义示例中 subject 返回的值

参见

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# File 'lib/rspec/core/memoized_helpers.rb', line 444
def subject(name=nil, &block)
  if name
    let(name, &block)
    alias_method :subject, name
    self::NamedSubjectPreventSuper.__send__(:define_method, name) do
      raise NotImplementedError, "`super` in named subjects is not supported"
    end
  else
    let(:subject, &block)
  end
end

#subject!(name = nil, &block) ⇒void

与 subject 相同，只是块由一个隐式的 before 钩子调用。这具有设置状态和提供对该状态的记忆引用的双重目的。

示例


class Thing
  def self.count
    @count ||= 0
  end
  def self.count=(val)
    @count += val
  end
  def self.reset_count
    @count = 0
  end
  def initialize
    self.class.count += 1
  end
end
RSpec.describe Thing do
  after(:example) { Thing.reset_count }
  context "using subject" do
    subject { Thing.new }
    it "is not invoked implicitly" do
      Thing.count.should eq(0)
    end
    it "can be invoked explicitly" do
      subject
      Thing.count.should eq(1)
    end
  end
  context "using subject!" do
    subject!(:thing) { Thing.new }
    it "is invoked implicitly" do
      Thing.count.should eq(1)
    end
    it "returns memoized version on first invocation" do
      subject
      Thing.count.should eq(1)
    end
  end
end
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# File 'lib/rspec/core/memoized_helpers.rb', line 510
def subject!(name=nil, &block)
  subject(name, &block)
  before { subject }
end