我可以在自定义匹配器中使用内置 RSpec 匹配器吗？

Question

我对功能规范有以下期望（相当低级但仍然必要）：

expect(Addressable::URI.parse(current_url).query_values).to include(
  'some => 'value',
  'some_other' => String
)

请注意，第二个查询值是模糊匹配，因为我只想确保它存在，但我无法对其进行更具体的说明。

我想将其提取到自定义匹配器中。我开始于：

RSpec::Matchers.define :have_query_params do |expected_params|
  match do |url|
    Addressable::URI.parse(url).query_values == expected_params
  end
end

但这意味着我不能在那里传递 {'some_other' => String}。要继续使用模糊匹配，我必须在我的自定义匹配器中使用 include 匹配器。

但是，RSpec::Matchers::BuiltIn 中的任何内容都被标记为私有 API，而 Include 特别是 documented 为：

# Provides the implementation for `include`.
# Not intended to be instantiated directly.

所以，我的问题是：是否在 RSpec 支持的自定义匹配器中使用内置匹配器？ 我该怎么做？

Answer 1

RSpec::Matchers appears to be a supported API (its rdoc doesn't say otherwise), so you can write your matcher in Ruby instead of in the matcher DSL (which is supported; see the second paragraph of the custom matcher documentation) 并像这样使用 RSpec::Matchers#include：

spec/support/matchers.rb

module My
  module Matchers
    def have_query_params(expected)
      HasQueryParams.new expected
    end

    class HasQueryParams
      include RSpec::Matchers

      def initialize(expected)
        @expected = expected
      end

      def matches?(url)
        actual = Addressable::URI.parse(url).query_values
        @matcher = include @expected
        @matcher.matches? actual
      end

      def failure_message
        @matcher.failure_message
      end

    end
  end
end

spec/support/matcher_spec.rb

include My::Matchers

describe My::Matchers::HasQueryParams do
  it "matches" do
    expect("http://example.com?a=1&b=2").to have_query_params('a' => '1', 'b' => '2')
  end
end

Answer 2

是的，您可以从自定义匹配器中调用内置 rspec 匹配器。换句话说，您可以在编写匹配器时使用普通的 Rspec DSL 而不是纯 Ruby。查看 this gist（不是我的要点，但对我有帮助！）。

我有一个非常复杂的控制器，它有一个选项卡式界面，其中定义和选择的选项卡取决于模型实例的状态。我需要在 :new、:create、:edit 和 :update 操作的每个状态下测试选项卡设置。所以我写了这些匹配器：

require "rspec/expectations"

RSpec::Matchers.define :define_the_review_tabs do
  match do
    expect(assigns(:roles         )).to be_a_kind_of(Array)
    expect(assigns(:creators      )).to be_a_kind_of(ActiveRecord::Relation)
    expect(assigns(:works         )).to be_a_kind_of(Array)

    expect(assigns(:available_tabs)).to include("post-new-work")
    expect(assigns(:available_tabs)).to include("post-choose-work")
  end

  match_when_negated do
    expect(assigns(:roles         )).to_not be_a_kind_of(Array)
    expect(assigns(:creators      )).to_not be_a_kind_of(ActiveRecord::Relation)
    expect(assigns(:works         )).to_not be_a_kind_of(Array)

    expect(assigns(:available_tabs)).to_not include("post-new-work")
    expect(assigns(:available_tabs)).to_not include("post-choose-work")
  end

  failure_message do
    "expected to set up the review tabs, but did not"
  end

  failure_message_when_negated do
    "expected not to set up review tabs, but they did"
  end
end

RSpec::Matchers.define :define_the_standalone_tab do
  match do
    expect(assigns(:available_tabs)).to include("post-standalone")
  end

  match_when_negated do
    expect(assigns(:available_tabs)).to_not include("post-standalone")
  end

  failure_message do
    "expected to set up the standalone tab, but did not"
  end

  failure_message_when_negated do
    "expected not to set up standalone tab, but they did"
  end
end

RSpec::Matchers.define :define_only_the_review_tabs do
  match do
    expect(assigns).to     define_the_review_tabs
    expect(assigns).to_not define_the_standalone_tab
    expect(assigns(:selected_tab)).to eq(@selected) if @selected
  end

  chain :and_select do |selected|
    @selected = selected
  end

  failure_message do
    if @selected
      "expected to set up only the review tabs and select #{@selected}, but did not"
    else
      "expected to set up only the review tabs, but did not"
    end
  end
end

RSpec::Matchers.define :define_only_the_standalone_tab do
  match do
    expect(assigns).to     define_the_standalone_tab
    expect(assigns).to_not define_the_review_tabs
    expect(assigns(:selected_tab)).to eq("post-standalone")
  end

  failure_message do
    "expected to set up only the standalone tab, but did not"
  end
end

RSpec::Matchers.define :define_all_tabs do
  match do
    expect(assigns).to define_the_review_tabs
    expect(assigns).to define_the_standalone_tab
    expect(assigns(:selected_tab)).to eq(@selected) if @selected
  end

  chain :and_select do |selected|
    @selected = selected
  end

  failure_message do
    if @selected
      "expected to set up all three tabs and select #{@selected}, but did not"
    else
      "expected to set up all three tabs, but did not"
    end
  end
end

我是这样使用它们的：

should define_all_tabs.and_select("post-choose-work")
should define_all_tabs.and_select("post-standalone")
should define_only_the_standalone_tab
should define_only_the_review_tabs.and_select("post-choose-work")
should define_only_the_review_tabs.and_select("post-new-work")

能够将几块重复的期望并将它们汇总到一组自定义匹配器中，而无需在纯 Ruby.

中编写匹配器，真是太棒了

这为我节省了几十行代码，使我的测试更具表现力，并且允许我在填充这些选项卡的逻辑发生变化时在一处进行更改。

另请注意，您可以在自定义匹配器中访问 methods/variables，例如 assigns 和 controller，因此您无需显式传递它们。

最后，我可以在规范中内联定义这些匹配器，但我选择将它们放在 spec/support/matchers/controllers/posts_controller_matchers.rb

中

Answer 3

您可以使用匹配器 DSL 而不是自己编写 Matcher class。比较简单

RSpec::Matchers.define :have_query_params do |expected|
  match do |actual|
    # your code
    RSpec::Matchers::BuiltIn::Include.new(expected).matches?(actual)
  end
end

我可以在自定义匹配器中使用内置 RSpec 匹配器吗？

Can I use a built-in RSpec matcher in a custom matcher?

ruby

rspec

rspec-expectations