Rspec negated change matcher

negated_change_matcher.rb

# This should be in rspec core, but add it here so we can chain negative change expectations, like
# expect { do_thing }.to change {a}.and not_change {b}.and change {b}
RSpec::Matchers.define_negated_matcher :not_change, :change

When expecting multiple things to happen given some code block, sometimes you want some things not to change. This is annoying with the default matchers in rspec, so define this in an rspec initializer.

expect { something }
    .to change { a }.from(this).to(that)
    .and not_change { b }
    .and change { c } # etc