```ruby
require 'spec_helper'

describe DisableEmailInterceptor do
  before do
    ActionMailer::Base.register_interceptor(DisableEmailInterceptor)
  end

  it 'should not send emails' do
    Gitlab.config.gitlab.stub(:email_enabled).and_return(false)
    expect {
      deliver_mail
    }.not_to change(ActionMailer::Base.deliveries, :count)
  end

  after do
    Mail.class_variable_set(:@@delivery_interceptors, [])
  end

  def deliver_mail
    key = create :personal_key
    Notify.new_ssh_key_email(key.id)
  end
end
```

Add a comment in interceptor spec.
user
```ruby
require 'spec_helper'

describe DisableEmailInterceptor do
  before do
    ActionMailer::Base.register_interceptor(DisableEmailInterceptor)
  end

  it 'should not send emails' do
    Gitlab.config.gitlab.stub(:email_enabled).and_return(false)
    expect {
      deliver_mail
    }.not_to change(ActionMailer::Base.deliveries, :count)
  end

  after do
    # Removing interceptor from the list because unregister_interceptor is
    # implemented in later version of mail gem
    # See: https://github.com/mikel/mail/pull/705
    Mail.class_variable_set(:@@delivery_interceptors, [])
  end

  def deliver_mail
    key = create :personal_key
    Notify.new_ssh_key_email(key.id)
  end
end
```
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