How to test exception raising in Rails/RSpec?

Question

There is the following code:

def index
    @car_types = car_brand.car_types
end

def car_brand
    CarBrand.find(params[:car_brand_id])
rescue ActiveRecord::RecordNotFound
    raise Errors::CarBrandNotFound.new 
end

I want to test it through RSpec. My code is:

it 'raises CarBrandNotFound exception' do
    get :index, car_brand_id: 0
    expect(response).to raise_error(Errors::CarBrandNotFound)
end

CarBrand with id equaling 0 doesn't exist, therefore my controller code raises Errors::CarBrandNotFound, but my test code tells me that nothing was raised. How can I fix it? What do I wrong?

score 177 · Answer 1 · edited Jan 12 '21 at 11:56

177

Use expect{} instead of expect().

Example:

it do 
  expect { response }.to raise_error(Errors::CarBrandNotFound)
end

edited Jan 12 '21 at 11:56

Greg

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answered Sep 18 '14 at 09:37

kaleb4eg

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It's worth pointing out that this solves the issue because the {} syntax creates a block to monitor for the given exception to be raised. MiniTest has similar syntax requirements when checking that a block of code raises an exception. – Argus9 May 15 '17 at 18:34
5

I can't believe it. 1 hour of trying and it's just turning `( )` into `{ }`! Thank you so much – Simon Franzen Feb 12 '19 at 12:20
1

I wasn't able to get this method working in Rails 7 – Paul Danelli Jan 30 '22 at 13:00

score 153 · Answer 2 · edited Mar 29 '23 at 17:24

153

In order to spec error handling, your expectations need to be set on a block; evaluating an object cannot raise an error.

So you want to do something like this:

expect {
  get :index, car_brand_id: 0
}.to raise_error(Errors::CarBrandNotFound)

I am a bit surprised that you don't get any exception bubbling up to your spec results, though.

edited Mar 29 '23 at 17:24

aarona

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answered Mar 03 '14 at 08:21

Jakob S

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@jakob-s the expect error behaviour that you're using here doesn't work on controller requests. The `get :index, car_brand_id: 0` itself doesn't raise an error. – rikas Mar 11 '15 at 18:00
@RicardoOtero Things might have changed, but for what it's worth, it does for me: https://gist.github.com/koppen/0e1d0894a908a3768847. But certainly, something in the stack might be handling the error before it bubbles up to the spec runner. – Jakob S Mar 13 '15 at 09:41
This is the right answer for current rspec versions ans should be voted up – Neil Woods Mar 20 '15 at 22:34
That is correct. The correct form to to test exceptions is using {} instead of () on except method. – Luiz Henrique Jan 12 '17 at 04:23

score 18 · Answer 3 · answered Mar 03 '14 at 09:33

18

get :index will never raise an exception - it will rather set response to be an 500 error some way as a real server would do.

Instead try:

it 'raises CarBrandNotFound exception' do
  controller.params[:car_brand_id] = 0
  expect{ controller.car_brand }.to raise_error(Errors::CarBrandNotFound)
end

answered Mar 03 '14 at 09:33

BroiSatse

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I'm glad that someone mentioned this! :) Jakob tried to educate them that it will never raise an exception in the most upvoted answer but he was faced with some incorrect resistance. – Tarek N. Elsamni Jan 21 '19 at 13:09

score 4 · Answer 4 · answered Mar 29 '23 at 17:28

4

If you want to test the message that comes along with the exception, you can also do something like this:

it do 
  expect { response }.to raise_error(Errors::CarBrandNotFound, "Ford not found")
end

answered Mar 29 '23 at 17:28

aarona

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How to test exception raising in Rails/RSpec?

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