Using instance_variable_set in testing

[Rachel Moser]

In #ruby-testing I have been told to use instance_variable_set and I have been told that it is a code smell. Is it a code smell when used only in testing?

An an example, is it better to add guess as a parameter, so that one can create a new instance of game for tests subject(:game) { described_class.new(0, 9, 4) }

def initialize(min, max, guess = nil)
  @min = min
  @max = max
  @guess = guess
end

Or is it better to have two arguments and to use game.instance_variable_set(:@guess, 4) in the tests that require a value for @guess?

def initialize(min, max)
  @min = min
  @max = max
  @guess = nil
end