Rails test helper for stubbing a constant

When Googling for how to mock or stub a constant in your Rails test suite, I found out about RSpec's stub_const method. I don't use RSpec though, so I wrote this.

The way I use it is to include it in ActiveSupport::TestCase somewhere in test/test_helper.rb.

class ActiveSupport::TestCase
  include WithStubbedConst
  ...
end

	module WithStubbedConst
	def with_stubbed_const(consts, scope=self.class)
	stash = {}
	consts.each_pair do |key, val|
	stash[key] = scope.send(:remove_const, key)
	scope.send(:const_set, key, val)
	end
	begin
	yield
	ensure
	consts.each_pair do |key, val|
	scope.send(:remove_const, key)
	scope.send(:const_set, key, stash[key])
	end
	end
	end
	end

view raw with_stubbed_const.rb hosted with ❤ by GitHub

	require 'test/unit'
	require 'test_helper/with_stubbed_const'
	class TestWithStubbedConst < Test::Unit::TestCase
	include WithStubbedConst
	module Bar
	BAZ = 10
	end
	FOO = "foo"
	def test_default_scope
	assert_equal "foo", FOO
	with_stubbed_const(:FOO => "changed!") { assert_equal "changed!", FOO }
	assert_equal "foo", FOO
	end
	def test_specified_scope
	assert_equal 10, Bar::BAZ
	with_stubbed_const({:BAZ => 20}, Bar) { assert_equal 20, Bar::BAZ }
	assert_equal 10, Bar::BAZ
	end
	def test_block_raises
	assert_equal "foo", FOO
	with_stubbed_const(:FOO => 99) { assert_equal 99, FOO; raise "boom" } rescue nil
	assert_equal "foo", FOO
	end
	end

view raw with_stubbed_const_test.rb hosted with ❤ by GitHub