Prevent infinite loop when interpolating a null double as an integer …

…into a string.

Closes rspec#154.

Changelog.md

@@ -15,6 +15,8 @@ Bug fixes
 * Infinite loop generated by using `any_instance` and `dup`. (Sidu Ponnappa @kaiwren)
 * `double.should_receive(:foo).at_least(:once).and_return(a)` always returns a
   even if `:foo` is already stubbed.
+* Prevent infinite loop when interpolating a null double into a string
+  as an integer (`"%i" % double.as_null_object`). (Myron Marston)
 
 ### 2.10.1 / 2012-05-05
 [full changelog](http://github.com/rspec/rspec-mocks/compare/v2.10.0...v2.10.1)

lib/rspec/mocks/test_double.rb

@@ -64,8 +64,10 @@ def __initialize_as_test_double(name=nil, stubs_and_options={})
       end
 
       def method_missing(message, *args, &block)
-          raise NoMethodError if message == :to_ary
+        raise NoMethodError if message == :to_ary
+        return 0 if message == :to_int && __mock_proxy.null_object?
         __mock_proxy.record_message_received(message, *args, &block)
+
         begin
           __mock_proxy.null_object? ? self : super
         rescue NameError

spec/rspec/mocks/null_object_mock_spec.rb

@@ -15,6 +15,14 @@ module Mocks
         @double.stub(:foo)
         @double.should respond_to(:foo)
       end
+
+      it "raises an error when interpolated in a string as an integer" do
+        expected_error = RUBY_VERSION =~ /1.8/ ?
+                         TypeError :
+                         RSpec::Mocks::MockExpectationError
+
+        expect { "%i" % @double }.to raise_error(expected_error)
+      end
     end
 
     describe "a double acting as a null object" do
@@ -59,6 +67,14 @@ module Mocks
         @double.message(:expected_arg)
         @double.message(:unexpected_arg)
       end
+
+      it "can be interpolated in a string as an integer" do
+        # This form of string interpolation calls
+        # @double.to_int.to_int.to_int...etc until it gets an integer,
+        # and thus gets stuck in an infinite loop unless our double
+        # returns an int value from #to_int.
+        ("%i" % @double).should eq("0")
+      end
     end
 
     describe "#as_null_object" do