Climate Control RSpec helper https://github.com/thoughtbot/climate_control

climate_control_helpers.rb

module ClimateControlHelpers
  # Usage:
  #
  #    describe Foo do
  #      stub_envs(
  #        FOO: "bar",
  #      )
  #
  #      it "uses the ENVs"
  #    end
  #
  # Note that the hash values are evaluated at file-loading time.
  # If it needs to be dynamic, use a block:
  #
  #    describe Foo do
  #      let(:bar) { Time.now }
  #
  #      stub_envs do
  #        {
  #          FOO: bar,
  #        }
  #      end
  #
  #      it "uses the ENVs"
  #    end
  #
  def stub_envs(hash = {}, &)
    # This uses https://github.com/thoughtbot/climate_control.
    # When we used `allow(ENV)` we got intermittent errors, perhaps due to threading issues.
    around do |example|
      hash = block_given? ? instance_eval(&) : hash

      ClimateControl.modify(hash) { example.run }
    end
  end
end

RSpec.configure do |config|
  config.extend(ClimateControlHelpers)
end