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プロファイリングの例 (--profile)

--profile コマンドラインオプション（RSpec.configure から利用可能な #profile_examples）を設定すると、RSpec は最も遅い例のリストを出力します。デフォルトでは、最も遅い10個の例が表示されますが、表示する遅い例の数を変更することもできます。--profile と --fail-fast オプションを一緒に使用し、失敗がある場合は遅い例は表示されません。

背景​

spec/spec_helper.rb という名前のファイルがあるとします。


_And_ a file named "spec/example_spec.rb" with:

```ruby
require "spec_helper"

RSpec.describe "something" do
  it "0.1秒スリープする（例1）" do
    sleep 0.1
    expect(1).to eq(1)
  end

  it "0秒スリープする（例2）" do
    expect(2).to eq(2)
  end

  it "0.15秒スリープする（例3）" do
    sleep 0.15
    expect(3).to eq(3)
  end

  it "0.05秒スリープする（例4）" do
    sleep 0.05
    expect(4).to eq(4)
  end

  it "0.05秒スリープする（例5）" do
    sleep 0.05
    expect(5).to eq(5)
  end

  it "0.05秒スリープする（例6）" do
    sleep 0.05
    expect(6).to eq(6)
  end

  it "0.05秒スリープする（例7）" do
    sleep 0.05
    expect(7).to eq(7)
  end

  it "0.05秒スリープする（例8）" do
    sleep 0.05
    expect(8).to eq(8)
  end

  it "0.05秒スリープする（例9）" do
    sleep 0.05
    expect(9).to eq(9)
  end

  it "0.05秒スリープする（例10）" do
    sleep 0.05
    expect(10).to eq(10)
  end

  it "0.05秒スリープする（例11）" do
    sleep 0.05
    expect(11).to eq(11)
  end
end

## By default does not show profile

_When_ I run `rspec spec`

_Then_ the examples should all pass

_And_ the output should not contain "example 1"

_And_ the output should not contain "example 2"

_And_ the output should not contain "example 3"

_And_ the output should not contain "example 4"

_And_ the output should not contain "example 5"

_And_ the output should not contain "example 6"

_And_ the output should not contain "example 7"

_And_ the output should not contain "example 8"

_And_ the output should not contain "example 9"

_And_ the output should not contain "example 10"

_And_ the output should not contain "example 11".

## Setting `profile_examples` to true shows 10 examples

_Given_ a file named "spec/spec_helper.rb" with:

```ruby
RSpec.configure { |c| c.profile_examples = true }

_When_ I run `rspec spec`

_Then_ the examples should all pass

_And_ the output should contain "Top 10 slowest examples"

_And_ the output should contain "example 1"

_And_ the output should not contain "example 2"

_And_ the output should contain "example 3"

_And_ the output should contain "example 4"

_And_ the output should contain "example 5"

_And_ the output should contain "example 6"

_And_ the output should contain "example 7"

_And_ the output should contain "example 8"

_And_ the output should contain "example 9"

_And_ the output should contain "example 10"

_And_ the output should contain "example 11".

## Setting `profile_examples` to 2 shows 2 examples

_Given_ a file named "spec/spec_helper.rb" with:

```ruby
RSpec.configure { |c| c.profile_examples = 2 }

_When_ I run `rspec spec`

_Then_ the examples should all pass

_And_ the output should contain "Top 2 slowest examples"

_And_ the output should contain "example 1"

_And_ the output should not contain "example 2"

_And_ the output should contain "example 3"

_And_ the output should not contain "example 4"

_And_ the output should not contain "example 5"

_And_ the output should not contain "example 6"

_And_ the output should not contain "example 7"

_And_ the output should not contain "example 8"

_And_ the output should not contain "example 9"

_And_ the output should not contain "example 10"

_And_ the output should not contain "example 11".

## Setting profile examples through CLI using `--profile`

_When_ I run `rspec spec --profile 2`

_Then_ the examples should all pass

_And_ the output should contain "Top 2 slowest examples"

_And_ the output should contain "example 1"

_And_ the output should not contain "example 2"

_And_ the output should contain "example 3"

_And_ the output should not contain "example 4"

_And_ the output should not contain "example 5"

_And_ the output should not contain "example 6"

_And_ the output should not contain "example 7"

_And_ the output should not contain "example 8"

_And_ the output should not contain "example 9"

_And_ the output should not contain "example 10"

_And_ the output should not contain "example 11".

## Using `--no-profile` overrules config options

_Given_ a file named "spec/spec_helper.rb" with:

```ruby
RSpec.configure { |c| c.profile_examples = true }

_When_ I run `rspec spec --no-profile`

_Then_ the examples should all pass

_And_ the output should not contain "example 1"

_And_ the output should not contain "example 2"

_And_ the output should not contain "example 3"

_And_ the output should not contain "example 4"

_And_ the output should not contain "example 5"

_And_ the output should not contain "example 6"

_And_ the output should not contain "example 7"

_And_ the output should not contain "example 8"

_And_ the output should not contain "example 9"

_And_ the output should not contain "example 10"

_And_ the output should not contain "example 11".

## Using `--profile` with `--fail-fast` shows slow examples if everything passes

_When_ I run `rspec spec --fail-fast --profile`

_Then_ the examples should all pass

_And_ the output should contain "Top 10 slowest examples"

_And_ the output should contain "example 1"

_And_ the output should not contain "example 2"

_And_ the output should contain "example 3"

_And_ the output should contain "example 4"

_And_ the output should contain "example 5"

_And_ the output should contain "example 6"

_And_ the output should contain "example 7"

_And_ the output should contain "example 8"

_And_ the output should contain "example 9"

_And_ the output should contain "example 10"

_And_ the output should contain "example 11".

## Using `--profile` shows slow examples even in case of failures

_Given_ a file named "spec/example_spec.rb" with:

```ruby
require "spec_helper"

RSpec.describe "something" do
  it "0.1秒スリープする（例1）" do
    sleep 0.1
    expect(1).to eq(1)
  end

  it "失敗する" do
    fail
  end
end

_When_ I run `rspec spec --profile`

_Then_ the output should contain "2 examples, 1 failure"

_And_ the output should contain "Top 2 slowest examples"

_And_ the output should contain "example 1".

## Using `--profile` with `--fail-fast` doesn't show slow examples in case of failures

_Given_ a file named "spec/example_spec.rb" with:

```ruby
require "spec_helper"

RSpec.describe "something" do
  it "0.1秒間スリープする（例1）" do
    sleep 0.1
    expect(1).to eq(1)
  end

  it "失敗する" do
    fail
  end
end

_When_ I run `rspec spec --fail-fast --profile`

_Then_ the output should not contain "Top 2 slowest examples"

_And_ the output should not contain "example 1".

## Using `--profile` with slow before hooks includes hook execution time

_Given_ a file named "spec/example_spec.rb" with:

```ruby
RSpec.describe "slow before context hook" do
  before(:context) do
    sleep 0.2
  end

  context "ネストしたコンテキスト" do
    it "例" do
      expect(10).to eq(10)
    end
  end
end

RSpec.describe "slow example" do
  it "遅い例" do
    sleep 0.1
    expect(10).to eq(10)
  end
end

もし rspec spec --profile 1 を実行した場合

ならば 出力は「slow before context hook」を最も遅い例として報告する必要があります。