From: Leigh Daniels <lcdpublic@...>
Date: 2011-07-04T02:32:58+09:00
Subject: Ruby Koan Exception Testing Question

Hi all,

First, thanks to Jeremy for the Ruby Koans link.

Now I'm puzzled, Sensei!

I'm trying to write the code for the cases on lines 12 & 13 (see below) and I don't understand why they should be expected to raise exceptions. They appear to be isosceles triangles and pass the isosceles test.

Am I missing something subtle? Or something obvious?

**Leigh

"Things are not as they appear; nor are they otherwise."

---------------

The Master says:
  You have not yet reached enlightenment.
  I sense frustration. Do not be afraid to ask for help.

The answers you seek...
  TriangleError expected but nothing was raised.

Please meditate on the following code:
  /Users/leigh/koans/about_triangle_project_2.rb:12:in `test_illegal_triangles_throw_exceptions'

  def test_illegal_triangles_throw_exceptions
    assert_raise(TriangleError) do triangle(0, 0, 0) end
    assert_raise(TriangleError) do triangle(3, 4, -5) end
    assert_raise(TriangleError) do triangle(1, 1, 3) end  # line 12
    assert_raise(TriangleError) do triangle(2, 4, 2) end  # line 13
 end

These tests all pass, including two from the illegal exceptions test:

  def test_isosceles_triangles_have_exactly_two_sides_equal
    assert_equal :isosceles, triangle(3, 4, 4)  
    assert_equal :isosceles, triangle(4, 3, 4)
    assert_equal :isosceles, triangle(4, 4, 3)
    assert_equal :isosceles, triangle(10, 10, 2)
    
    assert_equal :isosceles, triangle(1, 1, 3) # these two are from
    assert_equal :isosceles, triangle(2, 4, 2) # test_illegal_triangles_throw_exceptions
  end

Here's the triangle method:

def triangle(a, b, c)
  if (a <= 0) || (b <= 0) || (c <= 0)
    raise TriangleError
  end
  case
  when (a == b) && (a == c) && (b == c)
    return :equilateral
  when (b == c) || (a == c) || (a == b) 
    return :isosceles
  when !(a == b) && !(a == c) && !(b == c)
    return :scalene
  else 
    return :oops!
  end
end