rspec/shoulda validate only positive values (numericality)

validate_positive.md

for something like this in rails model

...  
validates :points, :numericality => {:greater_than_or_equal_to => 0}, :allow_nil => true
...

test can be :

it { should validate_numericality_of(:points) }
it { should_not allow_value(-1).for(:points) }
it { should allow_value(0).for(:points) }