collatz-conjecture: New exercise with test generator

config.json

@@ -593,6 +593,18 @@
       "topics": [
 
       ]
+    },
+    {
+      "slug": "collatz-conjecture",
+      "difficulty": 1,
+      "topics": [
+        "Control-flow (loops)",
+        "Control-flow (conditionals)",
+        "Recursion",
+        "Integers",
+        "Algorithms",
+        "Mathematics"
+      ]
     }
   ],
   "deprecated": [

exercises/collatz-conjecture/.meta/.version

@@ -0,0 +1 @@
+1

exercises/collatz-conjecture/.meta/generator/collatz_conjecture_case.rb

@@ -0,0 +1,31 @@
+require 'generator/exercise_case'
+
+class CollatzConjectureCase < Generator::ExerciseCase
+  using Generator::Underscore
+
+  def workload
+    case expected
+    when Fixnum
+      standard_assertion
+    when Hash
+      error_assertion
+    end
+  end
+
+  def standard_assertion
+    assert_equal { subject_of_test }
+  end
+
+  def error_assertion
+    "assert_raises(ArgumentError) { #{subject_of_test} }"
+  end
+
+  def subject_of_test
+    "CollatzConjecture.steps(#{input})"
+  end
+
+  def input
+    number.underscore
+  end
+end
+

exercises/collatz-conjecture/.meta/solutions/collatz_conjecture.rb

@@ -0,0 +1,22 @@
+module BookKeeping
+  VERSION = 1
+end
+
+module CollatzConjecture
+  def self.steps(num)
+    raise ArgumentError if num < 1
+    n = num
+    steps = 0
+    until n == 1
+      steps += 1
+      if n.even?
+        n /= 2
+      else
+        n = 3 * n + 1
+      end
+    end
+    steps
+  end
+end
+
+

exercises/collatz-conjecture/collatz_conjecture_test.rb

@@ -0,0 +1,58 @@
+#!/usr/bin/env ruby
+require 'minitest/autorun'
+require_relative 'collatz_conjecture'
+
+# Common test data version: 1.1.1 25c4479
+class CollatzConjectureTest < Minitest::Test
+  def test_zero_steps_for_one
+    # skip
+    assert_equal 0, CollatzConjecture.steps(1)
+  end
+
+  def test_divide_if_even
+    skip
+    assert_equal 4, CollatzConjecture.steps(16)
+  end
+
+  def test_even_and_odd_steps
+    skip
+    assert_equal 9, CollatzConjecture.steps(12)
+  end
+
+  def test_large_number_of_even_and_odd_steps
+    skip
+    assert_equal 152, CollatzConjecture.steps(1_000_000)
+  end
+
+  def test_zero_is_an_error
+    skip
+    assert_raises(ArgumentError) { CollatzConjecture.steps(0) }
+  end
+
+  def test_negative_value_is_an_error
+    skip
+    assert_raises(ArgumentError) { CollatzConjecture.steps(-15) }
+  end
+
+  # Problems in exercism evolve over time, as we find better ways to ask
+  # questions.
+  # The version number refers to the version of the problem you solved,
+  # not your solution.
+  #
+  # Define a constant named VERSION inside of the top level BookKeeping
+  # module, which may be placed near the end of your file.
+  #
+  # In your file, it will look like this:
+  #
+  # module BookKeeping
+  #   VERSION = 1 # Where the version number matches the one in the test.
+  # end
+  #
+  # If you are curious, read more about constants on RubyDoc:
+  # http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html
+
+  def test_bookkeeping
+    skip
+    assert_equal 1, BookKeeping::VERSION
+  end
+end