Move spec/rubyspec to spec/ruby for consistency

* Other ruby implementations use the spec/ruby directory.
  [Misc #13792] [ruby-core:82287]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59979 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/ruby/library/mathn/integer/from_prime_division_spec.rb

@@ -0,0 +1,11 @@
+require File.expand_path('../../../../spec_helper', __FILE__)
+
+ruby_version_is ''...'2.5' do
+  require 'mathn'
+
+  describe "Integer.from_prime_division" do
+    it "reverses a prime factorization of an integer" do
+      Integer.from_prime_division([[2, 1], [3, 2], [7, 1]]).should == 126
+    end
+  end
+end

spec/ruby/library/mathn/integer/prime_division_spec.rb

@@ -0,0 +1,21 @@
+require File.expand_path('../../../../spec_helper', __FILE__)
+
+ruby_version_is ''...'2.5' do
+  require 'mathn'
+
+  describe "Integer#prime_division" do
+    it "performs a prime factorization of a positive integer" do
+      100.prime_division.should == [[2, 2], [5, 2]]
+    end
+
+    # Proper handling of negative integers has been added to MRI trunk
+    # in revision 24091. Prior to that, all versions of MRI returned nonsense.
+    it "performs a prime factorization of a negative integer" do
+      -26.prime_division.should == [[-1, 1], [2, 1], [13, 1]]
+    end
+
+    it "raises a ZeroDivisionError when is called on zero" do
+      lambda { 0.prime_division }.should raise_error(ZeroDivisionError)
+    end
+  end
+end