Verifying doubles in RSpec 3
RSpec 3 has verifying doubles. This breed of mock objects check that any methods being stubbed are present on an instance of a given class. They also check methods aren't called with the wrong number of arguments.
This dual approach allows you to move very quickly and test components in isolation, while
giving you confidence that your doubles are not a complete fiction.
You should always prefer using a verifying double to using an old-school
Using verifying doubles
class User def login ... end end user = instance_double(User) # instead of double(User, login: 'u123') expect(user).to receive(:login).and_return('u123') # works expect(user).to receive(:screen_name).and_return('u123') # raises "User does not implement: screen_name"
I strongly recommend to instantiate the
instance_double using the class objects (
User) instead of the class name string (
"User") as you see in the examples. If you use a non-existing class name, verifying doubles fail silently.
There is also an option
verify_doubled_constant_names which you can set in your
spec_helper.rb, but this one requires you to eager-load your entire model tree before running specs.
Verifying partial doubles
Verifying doubles in RSpec 2
For older RSpecs there is rspec-fire.