gistfile2.txt

$ ruby setter-return.rb
Loaded suite setter-return
Started
F
Finished in 0.008396 seconds.

  1) Failure:
test_return_value_of_setter(TestFoo) [setter-return.rb:17]:
<4> expected but was
<2>.

1 tests, 1 assertions, 1 failures, 0 errors
$

setter-return.rb

require 'test/unit'

class Foo
  attr_reader :bar

  def bar=(baz)
    @bar = baz * 2
  end
end

class TestFoo < Test::Unit::TestCase
  def setup
    @foo = Foo.new
  end

  def test_return_value_of_setter
    assert_equal 4, @foo.bar = 2
  end
end