I’ve been working on rewriting some legacy feature tests that have been unmaintained for several years as system tests. One of the most convenient methods I have found while creating these tests is have_attributes.

The RSpec documentation I linked to above is a great overview of the matcher. I have found that it’s useful to matching the result of a service object, processor or even a controller action when we expect the resulting model, or models to have particular attributes set, but do not need to match on the entire object.

Here’s a simple example of have_attributes in action:

class WidgetCreator 
  def create
    Widget.create(status: :enqueued)

RSpec.describe WidgetCreator do
  describe ".create" do
    subject { WidgetCreator.new.create }

    it "creates the widget" do
      expect { subject }.to change(Widget, :count).by(1) 

    it "marks the widget as enqueued" do
      expect(subject).to have_attributes(status: :enqueued)

have_attributes accepts a single attribute key-value pair, or multiple. If multiple attributes are provided, then all keys and values must match. This matcher also seems to function against any other object which exposes attributes using simple setter and getter methods - like ActiveModel::Model, Struct and OpenStruct. This is based on the implementation using __send__ to read each attribute key from the actual object before comparing the value.