RSpec: stubbing Kernel::sleep?

If you are calling sleep within the context of an object, you should stub it on the object, like so:

class Foo  def self.some_method    sleep 5  endendit "should call sleep" do  Foo.stub!(:sleep)  Foo.should_receive(:sleep).with(5)  Foo.some_methodend

The key is, to stub sleep on whatever "self" is in the context where sleep is called.

When the call to sleep is not within an object (while testing a rake task for example), you can add the following in a before block (rspec 3 syntax)

allow_any_instance_of(Object).to receive(:sleep)

If you're using Mocha, then something like this will work:

def setup  Kernel.stubs(:sleep)enddef test_my_sleepy_method  my_object.take_cat_nap!  Kernel.assert_received(:sleep).with(1800) #should take a half-hour paower-napend

Or if you're using rr:

def setup  stub(Kernel).sleependdef test_my_sleepy_method  my_object.take_cat_nap!  assert_received(Kernel) { |k| k.sleep(1800) }end

You probably shouldn't be testing more complex threading issues with unit tests. On integration tests, however, use the real Kernel.sleep, which will help you ferret out complex threading issues.