Add shared spec integer_ceil_precision

This spec can be shared between Integer#ceil and Float#ceil and
improves coverage of cases where precision is passed in.

core/float/ceil_spec.rb

@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
+require_relative '../integer/shared/integer_ceil_precision'
 
 describe "Float#ceil" do
+  context "with precision" do
+    it_behaves_like :integer_ceil_precision, :Float
+  end
+
   it "returns the smallest Integer greater than or equal to self" do
     -1.2.ceil.should eql( -1)
     -1.0.ceil.should eql( -1)

core/integer/ceil_spec.rb

@@ -1,11 +1,16 @@
 require_relative '../../spec_helper'
 require_relative 'shared/to_i'
 require_relative 'shared/integer_rounding'
+require_relative 'shared/integer_ceil_precision'
 
 describe "Integer#ceil" do
   it_behaves_like :integer_to_i, :ceil
   it_behaves_like :integer_rounding_positive_precision, :ceil
 
+  context "with precision" do
+    it_behaves_like :integer_ceil_precision, :Integer
+  end
+
   context "precision argument specified as part of the ceil method is negative" do
     it "returns the smallest integer greater than self with at least precision.abs trailing zeros" do
       18.ceil(-1).should eql(20)

core/integer/shared/integer_ceil_precision.rb

@@ -0,0 +1,36 @@
+describe :integer_ceil_precision, shared: true do
+  context "precision is zero" do
+    it "returns integer self" do
+      send(@method, 0).ceil(0).should.eql?(0)
+      send(@method, 123).ceil(0).should.eql?(123)
+      send(@method, -123).ceil(0).should.eql?(-123)
+    end
+  end
+
+  context "precision is positive" do
+    it "returns self" do
+      send(@method, 0).ceil(1).should.eql?(send(@method, 0))
+      send(@method, 0).ceil(10).should.eql?(send(@method, 0))
+
+      send(@method, 123).ceil(10).should.eql?(send(@method, 123))
+      send(@method, -123).ceil(10).should.eql?(send(@method, -123))
+    end
+  end
+
+  context "precision is negative" do
+    it "always returns 0 when self is 0" do
+      send(@method, 0).ceil(-1).should.eql?(0)
+      send(@method, 0).ceil(-10).should.eql?(0)
+    end
+
+    it "returns largest integer less than self with at least precision.abs trailing zeros" do
+      send(@method, 123).ceil(-1).should.eql?(130)
+      send(@method, 123).ceil(-2).should.eql?(200)
+      send(@method, 123).ceil(-3).should.eql?(1000)
+
+      send(@method, -123).ceil(-1).should.eql?(-120)
+      send(@method, -123).ceil(-2).should.eql?(-100)
+      send(@method, -123).ceil(-3).should.eql?(0)
+    end
+  end
+end