How to set class-scope constants in ruby?

Question

Super-beginner easy points ruby question. I'm trying to learn some ruby by programming the Project Euler problems. So I have a test

class ProjectEuler_tests < Test::Unit::TestCase
  @solution = 123456 # Not the answer so as not to be a spoiler
  def test_problem_1
    assert_equal(@solution, ProjectEuler1.new.solve)
  end
end

But this doesn't work, @solution is nil when the test runs. What is the proper way to assign it at the class scope?

Answer 1

Class constants in ruby start with an uppercase char:

class ProjectEuler_tests < Test::Unit::TestCase
  SOLUTION = 123456 # Not the answer so as not to be a spoiler
  def test_problem_1
    assert_equal(SOLUTION, ProjectEuler1.new.solve)
  end
end

Answer 2

Class variables in ruby are designated by "@@"

class ProjectEuler_tests < Test::Unit::TestCase
  @@solution = 123456 # Not the answer so as not to be a spoiler
  def test_problem_1
    assert_equal(@@solution, ProjectEuler1.new.solve)
  end
end

Edit: I missed the "constant" in the title