Rails 6 ActionController::TestCase stub a controller method

Question

I am new with Ruby/Rails and the testing frameworks within Ruby/Rails. I have a pre-validation method (external API) that validates the incoming request. For all test cases, I want to stub that call and test the remaining functionalities.

I am knowledgeable about testing and mocks/stubs/spies (mostly Mockito/Powermockito stuffs), but do not know my way around Rails testing. I tried looking into RSpec / MiniTest stuffs, but it is getting overwhelming.

I have a controller method like this:

def handler
      # validate
      request_validated = validate_request
      unless request_validated
        head :unauthorized
        return
      end

      #... remaining codes
end

def validate_request
     # validation with external API
end

I have controller tests set up using ActionController::TestCase. Prior to adding the validation stuffs, all my test cases have tested out. But I cannot stub around the validation check.

I would want to have something like

controller.stub(validate_request).then_and_return(true)   # need something of this sort

post :handler, as: :json, params: completed_service_parameters
assert_response :no_content

I'm open to using any library, though would prefer to use any Rails in-built, if there's anything. Thanks.

Answer 1

I ended up using 'minitest/stub_any_instance'

require 'minitest/stub_any_instance'

...
test 'test stub' do
      ...
      Controller.stub_any_instance(:function, return-value) do
        # perform the call within the stubbed block
        post :function, as: :json, params: { :param1 => 'random' }
      end
      ...
end