Issue stubbing with RSpec - ruby

Question

I am trying to understand why the result of these tests, the first test claims the method is not stubbed, however, the 2nd one is.
class Roll
def initialize
install if !installed?
end
def install; puts 'install'; end
end
describe Roll do
before do
class RollTestClass < Roll; end
RollTestClass.any_instance.stub(:install)
end
let(:roll_class) { RollTestClass }
let(:roll) { RollTestClass.new }
context 'when installed is true' do
before do
roll_class.any_instance.stub(:installed?).and_return(true)
end
it 'should not call install' do
expect(roll).to_not have_received(:install)
end
end
context 'when installed is false' do
before do
roll_class.any_instance.stub(:installed?).and_return(false)
end
it 'should call install' do
expect(roll).to have_received(:install)
end
end
end
It's also strange the error says expected to have received install, but I think that is likely just faulty feedback from the RSpec DSL. But maybe worth noting.
1) Roll when installed is true should not call install
Failure/Error: expect(roll).to_not have_received(:install)
#<RollTestClass:0x10f69ef78> expected to have received install, but that method has not been stubbed.

Answer 1

The "spy pattern" of RSpec requires that the objects have been previously stubbed. However, any_instance.stub doesn't actually stub the methods "for real" unless/until the method is invoked on a particular object. As such, the methods appears as being "unstubbed" and you get the error you're getting. Here's some code that demonstrates the change in definition:
class Foo
end
describe "" do
it "" do
Foo.any_instance.stub(:bar)
foo1 = Foo.new
foo2 = Foo.new
print_bars = -> (context) {puts "#{context}, foo1#bar is #{foo1.method(:bar)}, foo2#bar is #{foo2.method(:bar)}"}
print_bars['before call']
foo1.bar
print_bars['after call']
end
end
which produces the following output:
before call, foo1#bar is #<Method: Foo#bar>, foo2#bar is #<Method: Foo#bar>
after call, foo1#bar is #<Method: #<Foo:0x007fc0c3842ef8>.bar>, foo2#bar is #<Method: Foo#bar>
I reported this an issue on RSpec's github site and got this acknowledgement/response.
You can use the following alternative approach, which depends on the recently introduced expect_any_instance_of method.
class Roll
def initialize
install if !installed?
end
def install; puts 'install'; end
end
describe Roll do
before do
class RollTestClass < Roll; end
end
let(:roll_class) { RollTestClass }
let(:roll) { RollTestClass.new }
context 'when installed is true' do
before do
roll_class.any_instance.stub(:installed?).and_return(true)
end
it 'should not call install' do
expect_any_instance_of(roll_class).to_not receive(:install)
roll
end
end
context 'when installed is false' do
before do
roll_class.any_instance.stub(:installed?).and_return(false)
end
it 'should call install' do
expect_any_instance_of(roll_class).to receive(:install)
roll
end
end
end