littleowllabs/stub_env

module StubEnv
  module Helpers
    def stub_env(key_or_hash, value = nil)
      init_stub unless env_stubbed?
      if key_or_hash.is_a? Hash
        key_or_hash.each { |k, v| add_stubbed_value(k, v) }
      else
        add_stubbed_value key_or_hash, value
      end
    end

    private

    STUBBED_KEY = '__STUBBED__'

    def add_stubbed_value(key, value)
      allow(ENV).to receive(:[]).with(key).and_return(value)
      allow(ENV).to receive(:fetch).with(key).and_return(value)
      allow(ENV).to receive(:fetch).with(key, anything()) do |_, default_val|
        value || default_val
      end
    end

    def env_stubbed?
      ENV[STUBBED_KEY]
    end

    def init_stub
      allow(ENV).to receive(:[]).and_call_original
      allow(ENV).to receive(:fetch).and_call_original
      add_stubbed_value(STUBBED_KEY, true)
    end
  end
end