Add warning expecatation filter for undef initialize

* Closes #175

Changelog.md

@@ -1,4 +1,4 @@
-# v0.5.11 2014-04-xx
+# v0.5.11 2014-04-21
 
 Changes:
 
@@ -6,6 +6,8 @@ Changes:
 * Better require highjack based zombifier
 * Do not mutate nthref $1 to gvar $0
 * Use faster duplicate guarding hashing AST::Node intances
+* Fix lots of shadowed invalid ASTs
+* Fix undefine initialize warnings, Closes #175
 
 # v0.5.10 2014-04-06
 

lib/mutant/mutation.rb

@@ -43,7 +43,9 @@ module Mutant
     #
     def insert
       subject.public?
-      Loader::Eval.call(root, subject)
+      subject.warning_expectation.execute do
+        Loader::Eval.call(root, subject)
+      end
       self
     end
 

lib/mutant/subject/method/instance.rb

@@ -31,7 +31,15 @@ module Mutant
         # @api private
         #
         def prepare
-          scope.send(:undef_method, name)
+          expected_warnings =
+            if name.equal?(:initialize)
+              ["#{__FILE__}:#{__LINE__ + 5}: warning: undefining `initialize' may cause serious problems\n"]
+            else
+              []
+            end
+          WarningExpectation.new(expected_warnings).execute do
+            scope.send(:undef_method, name)
+          end
           self
         end
 

spec/unit/mutant/subject/method/instance_spec.rb

@@ -20,6 +20,12 @@ describe Mutant::Subject::Method::Instance do
 
     let(:scope) do
       Class.new do
+        attr_reader :bar
+
+        def initialize
+          @bar = :boo
+        end
+
         def foo
         end
       end
@@ -27,11 +33,36 @@ describe Mutant::Subject::Method::Instance do
 
     subject { object.prepare }
 
-    it 'undefines method on scope' do
-      expect { subject }.to change { scope.instance_methods.include?(:foo) }.from(true).to(false)
+    context 'on non initialize methods' do
+
+      it 'undefines method on scope' do
+        expect { subject }.to change { scope.instance_methods.include?(:foo) }.from(true).to(false)
+      end
+
+      it_should_behave_like 'a command method'
+
     end
 
-    it_should_behave_like 'a command method'
+    context 'on initialize method' do
+
+      let(:node) do
+        s(:def, :initialize, s(:args))
+      end
+
+      it 'does not write warnings' do
+        warnings = Mutant::WarningFilter.use do
+          subject
+        end
+        expect(warnings).to eql([])
+      end
+
+      it 'undefines method on scope' do
+        subject
+        expect { scope.new }.to raise_error(NoMethodError)
+      end
+
+      it_should_behave_like 'a command method'
+    end
   end
 
   describe '#source' do