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引数のマッチング

with を使用して、期待される引数を指定します。with で制約を設けた メッセージの期待値 は、 マッチする引数で呼び出された場合にのみ満たされます。許可されたメッセージ のための事前準備された応答は、引数が一致する場合にのみ使用されます。

  | To match...                                         | ...use an expression like:         | ...which matches calls like:                        |
  |-----------------------------------------------------|------------------------------------|-----------------------------------------------------|
  | Literal arguments                                   | `with(1, true)`                    | `foo(1, true)`                                      |
  | Literal arguments where one is a hash               | `with(1, {x: 1, y: 2})`            | `foo(1, x: 1, y: 2) (where last argument is a hash) |
  | Keyword arguments                                   | `with(x: 1, y: 2)`                 | `foo(x: 1, y: 2)` (where x and y are keywords)      |
  | Anything that supports case equality (`===`)        | `with(/bar/)`                      | `foo("barn")`                                       |
  | Any list of args                                    | `with(any_args)`                   | `foo()`</br>`foo(1)`</br>`foo(:bar, 2)`               |
  | Any sublist of args (like an arg splat)             | `with(1, any_args)`                | `foo(1)`</br>`foo(1, :bar, :bazz)`                   |
  | An empty list of args                               | `with(no_args)`                    | `foo()`                                             |
  | Anything for a given positional arg                 | `with(3, anything)`                | `foo(3, nil)`</br>`foo(3, :bar)`                     |
  | Against an interface                                | `with(duck_type(:each))`           | `foo([])`                                           |
  | A boolean                                           | `with(3, boolean)`                 | `foo(3, true)`</br>`foo(3, false)`                   |
  | A subset of a hash                                  | `with(hash_including(:a => 1))`    | `foo(:a => 1, :b => 2)`                             |
  | An excluded subset of a hash                        | `with(hash_excluding(:a => 1))`    | `foo(:b => 2)`                                      |
  | A subset of an array                                | `with(array_including(:a, :b))`    | `foo([:a, :b, :c])`                                 |
  | An excluded subset of an array                      | `with(array_excluding(:a, :b))`    | `foo([:c, :d])`                                     |
  | An instance of a specific class                     | `with(instance_of(Integer))`       | `foo(3)`                                            |
  | An object with a given module in its ancestors list | `with(kind_of(Numeric))`           | `foo(3)`                                            |
  | An object with matching attributes                  | `with(having_attributes(:a => 1))` | `foo(:a => 1, :b => 2)`                             |
  | Any RSpec matcher                                   | `with(<matcher>)`                  | `foo(<object that matches>)`                        |

基本的な例​

次の内容で "basic_example_spec.rb" という名前のファイルがあるとします:

RSpec.describe "Constraining a message expectation using with" do
  let(:dbl) { double }
  before { expect(dbl).to receive(:foo).with(1, anything, /bar/) }

  it "passes when the args match" do
    dbl.foo(1, nil, "barn")
  end

  it "fails when the args do not match" do
    dbl.foo(1, nil, "other")
  end
end

rspec basic_example_spec.rb を実行すると、

次の出力で失敗するはずです:

| 2 examples, 1 failure                                         |
|                                                               |
| Failure/Error: dbl.foo(1, nil, "other")                       |
| #<Double (anonymous)> received :foo with unexpected arguments |
| expected: (1, anything, /bar/)                                |
| got: (1, nil, "other")                                        |

キーワード引数の使用​

次の内容で "keyword_example_spec.rb" という名前のファイルがあるとします:

class WithKeywords
  def foo(bar: "")
  end
end

RSpec.describe "Constraining a message expectation using with" do
  let(:dbl) { instance_double(WithKeywords) }
  before { expect(dbl).to receive(:foo).with(bar: "baz") }

  it "passes when the args match" do
    dbl.foo(bar: "baz")
  end

  it "fails when the args do not match" do
    dbl.foo(bar: "incorrect")
  end
end

rspec keyword_example_spec.rb を実行すると、

次の出力で失敗するはずです:

| 2 examples, 1 failure                                                               |
|                                                                                     |
| Failure/Error: dbl.foo(bar: "incorrect")                                            |
| #<InstanceDouble(WithKeywords) (anonymous)> received :foo with unexpected arguments |
| expected: ({:bar=>"baz"})                                                           |
| got: ({:bar=>"incorrect"})                                                          |

ハッシュとキーワード引数を区別する Rubies でのキーワード引数の使用​

次の内容で "keyword_example_spec.rb" という名前のファイルがあるとします:

class WithKeywords
  def foo(bar: "")
  end
end

RSpec.describe "Constraining a message expectation using with" do
  let(:dbl) { instance_double(WithKeywords) }
  before { expect(dbl).to receive(:foo).with(bar: "baz") }

  it "fails when the args do not match due to a hash" do
    dbl.foo({bar: "also incorrect"})
  end
end

rspec keyword_example_spec.rb を実行すると、

次の出力で失敗するはずです:

| 1 example, 1 failure                                                                |
|                                                                                     |
| Failure/Error: dbl.foo({bar: "also incorrect"})                                     |
| #<InstanceDouble(WithKeywords) (anonymous)> received :foo with unexpected arguments |
| expected: ({:bar=>"baz"}) (keyword arguments)                                       |
| got: ({:bar=>"also incorrect"}) (options hash)                                      |

RSpec マッチャの使用​

次の内容で "rspec_matcher_spec.rb" という名前のファイルがあるとします:

RSpec.describe "Using a RSpec matcher" do
  let(:dbl) { double }
  before { expect(dbl).to receive(:foo).with(a_collection_containing_exactly(1, 2)) }

  it "passes when the args match" do
    dbl.foo([2, 1])
  end

  it "fails when the args do not match" do
    dbl.foo([1, 3])
  end
end

rspec rspec_matcher_spec.rb を実行すると、

次の出力で失敗するはずです:

| 2 examples, 1 failure                                         |
|                                                               |
| Failure/Error: dbl.foo([1, 3])                                |
| #<Double (anonymous)> received :foo with unexpected arguments |
| expected: (a collection containing exactly 1 and 2)           |
| got: ([1, 3])                                                 |

カスタムマッチャの使用​

次の内容で "custom_matcher_spec.rb" という名前のファイルがあるとします:

RSpec::Matchers.define :a_multiple_of do |x|
  match { |actual| (actual % x).zero? }
end

RSpec.describe "Using a custom matcher" do
  let(:dbl) { double }
  before { expect(dbl).to receive(:foo).with(a_multiple_of(3)) }

  it "passes when the args match" do
    dbl.foo(12)
  end

  it "fails when the args do not match" do
    dbl.foo(13)
  end
end

rspec custom_matcher_spec.rb を実行すると、

次の出力で失敗するはずです:

| 2 examples, 1 failure                                         |
|                                                               |
| Failure/Error: dbl.foo(13)                                    |
| #<Double (anonymous)> received :foo with unexpected arguments |
| expected: (a multiple of 3)                                   |
| got: (13)                                                     |

引数に基づいて異なる応答を返す​

次の内容で "responding_differently_spec.rb" という名前のファイルがあるとします:

RSpec.describe "Using #with to constrain responses" do
  specify "its response depends on the arguments" do
    dbl = double

    # Set a default for any unmatched args
    allow(dbl).to receive(:foo).and_return(:default)

    allow(dbl).to receive(:foo).with(1).and_return(1)
    allow(dbl).to receive(:foo).with(2).and_return(2)

    expect(dbl.foo(0)).to eq(:default)
    expect(dbl.foo(1)).to eq(1)
    expect(dbl.foo(2)).to eq(2)
  end
end

rspec responding_differently_spec.rb を実行すると、

すべての例がパスするはずです。