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

ruby unit-testing testing rspec

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, :changeexpect { eat(what: nil) }  .to raise_error  .and avoid_changing(cat, :status)

Inspired by this comment.

ruby unit-testing testing rspec

You could use the "rescue nil" idiom to shorten what you already have:

it { expect { eat(what: nil) rescue nil }.not_to change(cat, :status) }

ruby unit-testing testing rspec

In RSpec 3 you can chain the two tests into one. I find this to be more readable than the rescue nil approach.

it { expect { eat(what: nil) }.to raise_error.and not_to change(cat, :status)}

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