RSpec and stubbing parameters for a named scope

I'm try to write a spec for a named scope which is date dependent.

The spec:

it "should return 6 months of documents" do
    Date.stub!(:today).and_return(Date.new(2005, 03, 03))
    doc_1 = Factory.create(:document, :date => '2005-01-01')
    Document.past_six_months.should == [doc_1]
end

The named scope in the Document model:

named_scope :past_six_months,
  :conditions => ['date > ? AND date < ?', Date.today - 6.months, Date.today]

The spec fails with an empty array, and the query in test.log shows why:

SELECT * FROM "documents" WHERE (date > '2009-11-11' AND date < '2010-05-11')

i.e. it appears to be ignoring my stubbed Date method.

However, if I use a class method instead of a named scope then it passes:

def self.past_six_months
    find(:all, :conditions => ['date > ? AND date < ?', Date.today - 6.months, Date.today])
end

I would rather use the named scope approach but I don't understand why it isn't working.

===

In reply to @speicher:

Thanks, but Timecop doesn't seem to help here.

it "should return 6 months of documents" do
    d = Date.new(2005, 03, 01)
    Timecop.travel(开发者_如何学编程d)
    doc_1 = Factory.create(:document, :date => '2005-01-01')
    Document.past_six_months.should == [doc_1]
end

Still passes for the class method approach but not for the named scope.

I suspect that named_scope is doing some kind of manipulation on the passed conditions before actually evaluating them, meaning that Date.today is never called directly.

I think the problem is that Date.today is not being computed at run-time, but when the model is first read by rails. Try enclosing it in a lambda:

named_scope :past_six_months, lambda { {:conditions => ['date > ? AND date < ?', Date.today - 6.months, Date.today] } }

Save yourself some headaches and use the Timecop gem to fake a date or time.