```ruby
require 'spec_helper'

describe 'Settings in rake tasks' do
  it '#set should work' do
    rake { set :domain, 'localhost' }

    rake.domain.should == 'localhost'
    rake.settings.domain.should == 'localhost'
  end

  it '#settings ||= should work' do
    rake {
      set :version, '2'
      settings.version ||= '3'
    }

    rake.settings.version.should == '2'
    rake.version.should == '2'
  end

  it '#settings with lambdas should work' do
    rake {
      set :version, '42'
      set :path, lambda { "/var/www/#{version}" }
    }

    rake.path.should == "/var/www/42"
    rake.path?.should be_true
  end

  it '#settings with a bang should work' do
    begin
      rake {
        set :path, lambda { "/var/www/#{version!}" }
      }
      rake.path
      1.should == 2
    rescue Mina::Error => e
      e.message.should include "version"
    end
  end
end
```

Use raise_error in rake settings spec.
user
```ruby
require 'spec_helper'

describe 'Settings in rake tasks' do
  it '#set should work' do
    rake { set :domain, 'localhost' }

    rake.domain.should == 'localhost'
    rake.settings.domain.should == 'localhost'
  end

  it '#settings ||= should work' do
    rake {
      set :version, '2'
      settings.version ||= '3'
    }

    rake.settings.version.should == '2'
    rake.version.should == '2'
  end

  it '#settings with lambdas should work' do
    rake {
      set :version, '42'
      set :path, lambda { "/var/www/#{version}" }
    }

    rake.path.should == "/var/www/42"
    rake.path?.should be_true
  end

  it '#settings with a bang should work' do
    expect {
      rake {
        set :path, lambda { "/var/www/#{version!}" }
      }
      rake.path
    }.to raise_error(Mina::Error, /version/)
  end
end
```
assistant