pboling/rspec-stubbed_env

# frozen_string_literal: true

#
# ENV stubbing is opt-in, via a shared context, rather than global
#
# Usage:
#
# describe 'my stubbed test' do
#   include_context 'with stubbed env'
#   before do
#     stub_env('FOO' => 'is bar')
#     # or, equivalently:
#     stub_env(FOO: 'is bar')
#     # or, equivalently:
#     stub_env('FOO', 'is bar')
#     # or, equivalently:
#     stub_env(FOO: 'is bar')
#   end
#   it 'does a thing' do
#     expect(ENV['FOO']).to eq('is bar')
#   end
# end
#
# NOTE: This file was originally written by Liam Bennet (https://github.com/ljkbennett)
#       as part of the stub_env library (https://github.com/ljkbennett/stub_env).
#       It has evolved since then.
module RSpec
  module StubbedEnv
    # Helpers to unobtrusively stub ENV
    module TestHelpers
      # Can be called with all key value pairs to be stubbed as a hash:
      #
      #     stub_env('A' => 'B', 'C' => 'D', 'E' => 'F')
      #
      # Alternatively can be called one per ENV key-value pair to stub:
      #
      #     stub_env('A', 'B')
      #     stub_env('C', 'D')
      #     stub_env('E', 'F')
      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)
        key = key.to_s # Support symbols by forcing to string
        allow_brackets(key, value)
        allow_fetch(key, value)
        allow_values_at
      end

      def allow_brackets(key, value)
        allow(ENV).to(receive(:[]).with(key).and_return(value))
      end

      def allow_fetch(key, 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

      # Rides on the fetch stub!
      def allow_values_at
        allow(ENV).to(receive(:values_at)) do |*args|
          args.map { |arg| ENV.fetch(arg, nil) }
        end
      end

      def env_stubbed?
        ENV.fetch(STUBBED_KEY, nil)
      end

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