[SOLVED] RSpec test to expect only certain properties of an ActiveRecord model to change

RSpec test to expect only certain properties of an ActiveRecord model to change

I am successfully testing whether certain properties of an ActiveRecord model are updated. I also want to test that ONLY those properties have changed. I was hoping I could hook into the model's .changes or .previous_changes methods to verify the properties I expect to change are the only ones being changed.

UPDATE

Looking for something equivalent to the following (which doesn't work):

it "only changes specific properties" do
  model.do_change
  expect(model.changed - ["name", "age", "address"]).to eq([])
end

Solution

Try something like this

expect { model.method_that_changes_attributes }
  .to change(model, :attribute_one).from(nil).to(1)
  .and change(model, :attribute_two)

If the changes are not attributes, but relations you might need to reload the model:

# Assuming that model has_one :foo
expect { model.method_that_changes_relation }
  .to change { model.reload.foo.id }.from(1).to(5)

EDIT:

After some clarification from the OP comment:

You can do this then

# Assuming, that :foo and :bar can be changed, and rest can not

(described_class.attribute_names - %w[foo bar]).each |attribute|
  specify "does not change #{attribute}" do
    expect { model.method_that_changes_attributes }
      .not_to change(model, attribute.to_sym)
    end
  end
end

This is essentially what you need.

This solution has one issue though: it will call method_that_changes_attributes for each attribute, and this can be inefficient. If that's the case - you may want to make your own matcher that accepts an array of methods. Start here