Testing class which uses refinements with RSpec - ruby-on-rails

Question

Let's say I've got refinement
module RefinedString
refine String do
def remove_latin_letters
#code code code code
end
end
end
and I use it inside my class Speech:
class Speech
using RefinedString
def initialize(text)
#content = text.remove_latin_letters
end
end
I've written tests for refinement in RSpec and now I'm testing Speech class
describe Speech
let(:text) { "ąńńóyińg" }
it 'should call my refinement' do
expect(text).to receive(:remove_latin_letters)
Speech.new(text)
end
end
but I get RSpec::Mocks::MockExpectationError: "ąńńóyińg" does not implement: remove_latin_letter
I don't think mocking it is a good solution (but I may be wrong! Is mocking the solution here?)
so I tried
let(:text) { described_class::String.new("ąńńóyińg") }
but the result is the same.
I don't want to explicitly call using RefinedString inside my RSpec (it should figure it out on its own, right?)
How to make RSpec aware of my refined methods?

Answer 1

We always want to test behavior, rather than implementation. To my mind, refinements change the behavior of other classes by virtue of being included, rather than having their own behavior. To use a somewhat clumsy analogy, if we were to test the reproductive behavior of a virus, we would have to introduce it into a host cell. We are interested in what happens to the host when the virus takes over (so to speak).
One approach is to build test classes with and without the refinement, e.g.:
class TestClass
attr_reader :content
def initialize(text)
#content = text.remove_latin_letters
end
end
describe "when not using RefinedString" do
it "raises an exception" do
expect { TestClass.new("ąńńóyińg") }.to raise_error(NoMethodError)
end
end
class RefinedTestClass
using RefinedString
attr_reader :content
def initialize(text)
#content = text.remove_latin_letters
end
end
describe "when using RefinedString" do
it "removes latin letters" do
expect(RefinedTestClass.new("ąńńóyińg").content).to eq "ńńóń"
end
end