Rspec 3.0 How to mock a method replacing the parameter but with no return value?

user3060126 picture user3060126 · Apr 18, 2014 · Viewed 19.8k times · Source

I've searched a lot and just cannot figure this out although it seems basic. Here's a way simplified example of what I want to do.

Create a simple method that does something but doesn't return anything, such as:

class Test
  def test_method(param)
    puts param
  end
  test_method("hello")
end

But in my rspec test I need to pass a different parameter, such as "goodbye" instead of "hello." I know this has to do with stubs and mocks, and I've looking over the documentation but can't figure it out: https://relishapp.com/rspec/rspec-mocks/v/3-0/docs/method-stubs

If I do:

@test = Test.new
allow(@test).to_receive(:test_method).with("goodbye")

it tells me to stub out a default value but I can't figure out how to do it correctly.

Error message:

received :test_method with unexpected arguments
  expected: ("hello")
  got: ("goodbye")
Please stub a default value first if message might be received with other args as well.     

I am using rspec 3.0, and calling something like

@test.stub(:test_method)

is not allowed.

Answer

Jignesh Gohel picture Jignesh Gohel · Mar 30, 2017

How to set a default value that is explained at

and_call_original can configure a default response that can be overriden for specific args

require 'calculator'

RSpec.describe "and_call_original" do
  it "can be overriden for specific arguments using #with" do
    allow(Calculator).to receive(:add).and_call_original
    allow(Calculator).to receive(:add).with(2, 3).and_return(-5)

    expect(Calculator.add(2, 2)).to eq(4)
    expect(Calculator.add(2, 3)).to eq(-5)
  end
end

Source where I came to know about that can be found at https://makandracards.com/makandra/30543-rspec-only-stub-a-method-when-a-particular-argument-is-passed