Add spec for ObjectSpace#memsize_of

Author: eregon

spec/ruby/library/objectspace/memsize_of_spec.rb

@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+require 'objspace'
+
+describe "ObjectSpace.memsize_of" do
+  it "returns 0 for true, false and nil" do
+    ObjectSpace.memsize_of(true).should == 0
+    ObjectSpace.memsize_of(false).should == 0
+    ObjectSpace.memsize_of(nil).should == 0
+  end
+
+  it "returns 0 for small Integers" do
+    ObjectSpace.memsize_of(42).should == 0
+  end
+
+  it "returns an Integer for an Object" do
+    obj = Object.new
+    ObjectSpace.memsize_of(obj).should be_kind_of(Integer)
+    ObjectSpace.memsize_of(obj).should > 0
+  end
+
+  it "is larger if the Object has more instance variables" do
+    obj = Object.new
+    before = ObjectSpace.memsize_of(obj)
+    100.times do |i|
+      obj.instance_variable_set(:"@foo#{i}", nil)
+    end
+    after = ObjectSpace.memsize_of(obj)
+    after.should > before
+  end
+end