How do I stub a method to raise an error using Ruby MiniTest?

Question

I'm trying to test a Rails controller branch that is triggered when the model method raises an error.

def my_controller_method   @my_object = MyObject.find(params[:id])    begin     result = @my_object.my_model_method(params)   rescue Exceptions::CustomError => e     flash.now[:error] = e.message            redirect_to my_object_path(@my_object) and return   end    # ... rest irrelevant end 

How can I get a Minitest stub to raise this Error?

it 'should show redirect on custom error' do   my_object = FactoryGirl.create(:my_object)    # stub my_model_method to raise Exceptions::CustomError here    post :my_controller_method, :id => my_object.to_param   assert_response :redirect   assert_redirected_to my_object_path(my_object)   flash[:error].wont_be_nil end 

Answer 1

require "minitest/autorun"  class MyModel   def my_method; end end  class TestRaiseException < MiniTest::Unit::TestCase   def test_raise_exception     model = MyModel.new     raises_exception = -> { raise ArgumentError.new }     model.stub :my_method, raises_exception do       assert_raises(ArgumentError) { model.my_method }     end   end end 

Answer 2

One way to do this is to use Mocha, which Rails loads by default.

it 'should show redirect on custom error' do   my_object = FactoryGirl.create(:my_object)    # stub my_model_method to raise Exceptions::CustomError here   MyObject.any_instance.expects(:my_model_method).raises(Exceptions::CustomError)    post :my_controller_method, :id => my_object.to_param   assert_response :redirect   assert_redirected_to my_object_path(my_object)   flash[:error].wont_be_nil end