hello.rb

class Hello
  def greeting(name)
    "Hello, #{name}!"
  end
end

hello_spec.rb

require_relative 'hello'

describe Hello do
  describe "#greeting" do
    it "returns a greeting" do
      expect(Hello.new.greeting("Test")).to eq("Hello, Test!")
    end

    it "returns another greeting" do
      expect(Hello.new.greeting("Kristin")).to eq("Hello, Kristin")
    end
  end
end