How do I `expect` something which raises exception in RSpec?

Question

I have a method which performs some actions on Cat model and in case of incorrect input raises an exception:

context "hungry cat" do   it { expect { eat(what: nil) }.to raise_error }  end 

What I want to do is to check whether this method change cats status, like that:

context "hungry cat" do   it { expect { eat(what: nil) }.to raise_error }    it { expect { eat(what: nil) }.not_to change(cat, :status) }  end 

The problem is that since eat(what: nil) will raise an exception the second it will fail no matter what. So, is it possible to ignore exception and check some condition?

I know that it's possible to do something like:

it do    expect do     begin       eat(what: nil)     rescue     end   end.not_to change(cat, :status) end 

But it's way too ugly.

Answer 1

You can chain positive assertions with and. If you want to mix in a negated one in the chain, RSpec 3.1 introduced define_negated_matcher.

You could do something like:

RSpec::Matchers.define_negated_matcher :avoid_changing, :change  expect { eat(what: nil) }   .to raise_error   .and avoid_changing(cat, :status) 

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