Testing after_create with rspec - ruby

Question

I have code in my model.
class Foo < ActiveRecord::Base
after_create :create_node_for_foo
def create_node_for_user
FooBar.create(id: self.id)
end
end
and have code in rspec of Foo model
describe Foo do
let (:foo) {FactoryGirl.create(:foo)}
subject { foo }
it { should respond_to(:email) }
it { should respond_to(:fullname) }
it "have mass assignable attributes" do
foo.should allow_mass_assignment_of :email
foo.should allow_mass_assignment_of :fullname
end
it "create node in graph database" do
foo1 = FactoryGirl.create(:foo)
FooBar.should_receive(:create).with(id: foo1.id)
end
end
but my test is failing with message
Failures:
1) Foo create node in graph database on
Failure/Error: FooBar.should_receive(:create).with(id: foo1.id)
(<FooBar (class)>).create({:id=>18})
expected: 1 time
received: 0 times
What might be wrong?

Answer 1

Okay got around with problem
changed this
it "create node in graph database" do
foo1 = FactoryGirl.create(:foo)
FooBar.should_receive(:create).with(id: foo1.id)
end
to
it "create node in graph database" do
foo1 = FactoryGirl.build(:foo)
FooBar.should_receive(:create).with(id: foo1.id)
foo1.save
end

Answer 2

A bit late to the party but actually the above won't work. You can create a custom matcher to do it:
class EventualValueMatcher
def initialize(&block)
#block = block
end
def ==(value)
#block.call == value
end
end
def eventual_value(&block)
EventualValueMatcher.new(&block)
end
Then in your spec do:
it "create node in graph database" do
foo1 = FactoryGirl.build(:foo)
FooBar.should_receive(:create).with(eventual_value { { id: foo1.id } })
foo1.save
end
This means that the mock will not evaluate the block until after the fact and it has actually been set.

Answer 3

In case it helps someone, an updated version of Dan Draper solution to use a custom matcher with a block, would be like this:
# spec/support/eventual_value_matcher.rb
RSpec::Matchers.define :eventual_value do |expected|
match do |actual|
actual == expected.call
end
end
And usage:
require "support/eventual_value_matcher" # or you can do a global require on the rails_helper.rb file
it "xxx" do
foo1 = FactoryGirl.build(:foo)
expect(FooBar).to receive(:create).with(eventual_value(proc { foo1.id }))
foo.save!
end