Example of switching positive/negative in compound expectations

example.rb

describe 'some destructive method' do
  it 'destroys only relevant things' do
    expect { do_something_destructive }.to change { things_to_destroy.reload.count }.to(0)
                               .and.not_to change { things_not_to_destroy.reload.count }
                                 # ^^^^^^^ This is what I want to do and just a fictional syntax.
  end
end

Here's what you can do that works:

RSpec::Matchers.define_negated_matcher :avoid_changing, :change

describe 'some destructive method' do
  it 'destroys only relevant things' do
    expect {
      do_something_destructive
    }.to change { things_to_destroy.reload.count }.to(0)
     .and avoid_changing { things_not_to_destroy.reload.count }
  end
end