```ruby
module Motion
  def default_movement
    "walking"
    end
  end
end

```
        

```ruby
RSpec.describe "Ruby composition methods" do
  describe "extend" do
    context "when a class extends a module" do
      it "adds the module methods to the class's class methods" do
        expect(Person.default_movement).to eq("walking")
      end

      it "does not add the module methods to the class's instance methods" do
        person = Person.new

        expect { person.default_movement }.to raise_error(NoMethodError)
      end
    end

    context "when an object extends a module" do
      it "gains the modules methods" do
        cat = Cat.new

        cat.extend(Speech)
        expect(cat.greet).to eq("Hello World")
      end
    end
  end
end
```