Add expression => self mutation

Also reorganizes parts of meta to align filenames to node name better.

Closes #191

lib/mutant.rb

@@ -159,6 +159,8 @@ require 'mutant/mutator/node/named_value/variable_assignment'
 require 'mutant/mutator/node/loop_control'
 require 'mutant/mutator/node/noop'
 require 'mutant/mutator/node/or_asgn'
+require 'mutant/mutator/node/and_asgn'
+require 'mutant/mutator/node/defined'
 require 'mutant/mutator/node/op_asgn'
 require 'mutant/mutator/node/conditional_loop'
 require 'mutant/mutator/node/yield'

lib/mutant/meta/example/dsl.rb

@@ -74,6 +74,17 @@ module Mutant
           self
         end
 
+        # Add singleotn mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def singleton_mutations
+          mutation 'nil'
+          mutation 'self'
+        end
+
         # Helper method to coerce input to node
         #
         # @param [String,Parser::AST::Node] input

lib/mutant/mutator/node.rb

@@ -23,8 +23,8 @@ module Mutant
           children.at(index)
         end
 
-        define_method("emit_#{name}_mutations") do
+        define_method("emit_#{name}_mutations") do |&block|
-          mutate_child(index)
+          mutate_child(index, &block)
         end
 
         define_method("emit_#{name}") do |node|
@@ -118,12 +118,15 @@ module Mutant
       #
       # @api private
       #
-      def mutate_child(index, mutator = Mutator)
+      def mutate_child(index, mutator = Mutator, &block)
+        block ||= lambda { |_node| true }
         child = children.at(index)
         mutator.each(child, self) do |mutation|
+          if block.call(mutation)
             emit_child_update(index, mutation)
           end
         end
+      end
 
       # Emit delete child mutation
       #
@@ -166,7 +169,28 @@ module Mutant
         emit(new_self(*children))
       end
 
-      # Emit a new AST node with NilLiteral class
+      # Emit singleton literals
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def emit_singletons
+        emit_nil
+        emit_self
+      end
+
+      # Emit a literal self
+      #
+      # @return [undefined]
+      #
+      # @api private
+      #
+      def emit_self
+        emit(N_SELF)
+      end
+
+      # Emit a literal nil
       #
       # @return [undefined]
       #

lib/mutant/mutator/node/and_asgn.rb

@@ -0,0 +1,34 @@
+# encoding: utf-8
+
+module Mutant
+  class Mutator
+    class Node
+
+      # OpAsgn mutator
+      class AndAsgn < self
+
+        handle(:and_asgn)
+
+        children :left, :right
+
+      private
+
+        # Emit mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def dispatch
+          emit_singletons
+          emit_left_mutations do |mutation|
+            !mutation.type.equal?(:self)
+          end
+          emit_right_mutations
+        end
+
+      end # OrAsgn
+    end # Node
+  end # Mutator
+end # Mutant
+

lib/mutant/mutator/node/binary.rb

@@ -24,7 +24,7 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil
+          emit_singletons
           emit(left)
           emit(right)
           mutate_operator

lib/mutant/mutator/node/block.rb

@@ -19,6 +19,7 @@ module Mutant
         # @api private
         #
         def dispatch
+          emit_singletons
           emit(send)
           emit_arguments_mutations
           if body
@@ -26,7 +27,6 @@ module Mutant
           end
           emit_body(nil)
           emit_body(RAISE)
-          emit_nil
         end
 
       end # Block

lib/mutant/mutator/node/case.rb

@@ -20,10 +20,10 @@ module Mutant
         # @api private
         #
         def dispatch
+          emit_singletons
           emit_condition_mutations if condition
           emit_when_mutations
           emit_else_mutations
-          emit_nil
         end
 
         # Emit when mutations

lib/mutant/mutator/node/conditional_loop.rb

@@ -20,11 +20,11 @@ module Mutant
         # @api private
         #
         def dispatch
+          emit_singletons
           emit_condition_mutations
           emit_body_mutations if body
           emit_body(nil)
           emit_body(RAISE)
-          emit_nil
         end
 
       end # While

lib/mutant/mutator/node/const.rb

@@ -18,7 +18,7 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil unless parent_type == :const
+          emit_singletons unless parent_type == :const
           emit_type(nil, *children.drop(1))
           children.each_with_index do |child, index|
             mutate_child(index) if child.kind_of?(Parser::AST::Node)

lib/mutant/mutator/node/defined.rb

@@ -0,0 +1,30 @@
+# encoding: utf-8
+
+module Mutant
+  class Mutator
+    class Node
+      # Namespace for define mutations
+      class Defined < self
+
+        handle(:defined?)
+
+        children :expression
+
+      private
+
+        # Emit mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def dispatch
+          emit_expression_mutations do |node|
+            !node.type.equal?(:self)
+          end
+        end
+
+      end # Defined
+    end # Node
+  end # Mutator
+end # Mutant

lib/mutant/mutator/node/dstr.rb

@@ -19,7 +19,7 @@ module Mutant
         #
         def dispatch
           super
-          emit_nil
+          emit_singletons
         end
 
       end # Dstr

lib/mutant/mutator/node/dsym.rb

@@ -19,7 +19,7 @@ module Mutant
         #
         def dispatch
           super
-          emit_nil
+          emit_singletons
         end
 
       end # Dsym

lib/mutant/mutator/node/generic.rb

@@ -10,7 +10,7 @@ module Mutant
         # These nodes still need a dedicated mutator,
         # your contribution is that close!
         handle(
-          :ensure, :redo, :defined?, :regopt, :retry, :arg_expr,
+          :ensure, :redo, :regopt, :retry, :arg_expr,
           :kwrestarg, :kwoptarg, :kwarg, :undef, :module, :empty,
           :alias, :for, :xstr, :back_ref, :class,
           :sclass, :match_with_lvasgn, :while_post,

lib/mutant/mutator/node/if.rb

@@ -19,10 +19,10 @@ module Mutant
         # @api private
         #
         def dispatch
+          emit_singletons
           mutate_condition
           mutate_if_branch
           mutate_else_branch
-          emit_nil
         end
 
         # Emit conditon mutations
@@ -32,7 +32,9 @@ module Mutant
         # @api private
         #
         def mutate_condition
-          emit_condition_mutations
+          emit_condition_mutations do |condition|
+            !condition.type.eql?(:self)
+          end
           emit_type(n_not(condition), if_branch, else_branch) unless condition.type == :match_current_line
           emit_type(N_TRUE,  if_branch, else_branch)
           emit_type(N_FALSE, if_branch, else_branch)

lib/mutant/mutator/node/kwbegin.rb

@@ -19,7 +19,7 @@ module Mutant
         #
         def dispatch
           super
-          emit_nil
+          emit_singletons
         end
 
       end # Kwbegin

lib/mutant/mutator/node/literal/array.rb

@@ -18,7 +18,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
             emit_type
             mutate_body
             if children.one?

lib/mutant/mutator/node/literal/fixnum.rb

@@ -18,7 +18,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
             emit_values(values)
           end
 

lib/mutant/mutator/node/literal/float.rb

@@ -18,7 +18,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
             emit_values(values)
             emit_special_cases
           end

lib/mutant/mutator/node/literal/hash.rb

@@ -18,7 +18,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
             emit_type
             mutate_body
           end

lib/mutant/mutator/node/literal/range.rb

@@ -26,7 +26,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
             emit_inverse
             emit_lower_bound_mutations
             emit_upper_bound_mutations

lib/mutant/mutator/node/literal/regex.rb

@@ -31,7 +31,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil unless parent_type == :match_current_line
+            emit_singletons unless parent_type == :match_current_line
             children.each_with_index do |child, index|
               mutate_child(index) unless child.type == :str
             end

lib/mutant/mutator/node/literal/string.rb

@@ -18,7 +18,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
           end
 
         end # String

lib/mutant/mutator/node/literal/symbol.rb

@@ -22,7 +22,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
             Mutator::Util::Symbol.each(value, self) do |value|
               emit_type(value)
             end

lib/mutant/mutator/node/loop_control.rb

@@ -24,9 +24,9 @@ module Mutant
         #
         def dispatch
           super
+          emit_singletons
           children.each_index(&method(:delete_child))
           emit(s(INVERSE.fetch(node.type), *children))
-          emit_nil
         end
 
       end # Next

lib/mutant/mutator/node/masgn.rb

@@ -20,7 +20,7 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil
+          emit_singletons
         end
 
       end # MultipleAssignment

lib/mutant/mutator/node/match_current_line.rb

@@ -17,7 +17,7 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil
+          emit_singletons
           emit_regexp_mutations
         end
 

lib/mutant/mutator/node/named_value/access.rb

@@ -19,7 +19,7 @@ module Mutant
           # @api private
           #
           def dispatch
-            emit_nil
+            emit_singletons
           end
 
         end # Access

lib/mutant/mutator/node/named_value/variable_assignment.rb

@@ -32,9 +32,9 @@ module Mutant
           # @api private
           #
           def dispatch
+            emit_singletons
             mutate_name
             emit_value_mutations if value # mlhs!
-            emit_nil
           end
 
           # Emit name mutations

lib/mutant/mutator/node/op_asgn.rb

@@ -5,9 +5,11 @@ module Mutant
     class Node
 
       # OpAsgn mutator
-      class OpAsgn < Generic
+      class OpAsgn < self
 
-        handle(:op_asgn, :and_asgn)
+        handle(:op_asgn)
+
+        children :left, :operation, :right
 
       private
 
@@ -18,8 +20,11 @@ module Mutant
         # @api private
         #
         def dispatch
-          super
+          emit_singletons
-          emit_nil
+          emit_left_mutations do |mutation|
+            !mutation.type.equal?(:self)
+          end
+          emit_right_mutations
         end
 
       end # OpAsgn

lib/mutant/mutator/node/or_asgn.rb

@@ -20,8 +20,12 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil
+          emit_singletons
-          emit_left_mutations unless left.type.equal?(:ivasgn)
+          unless left.type.equal?(:ivasgn)
+            emit_left_mutations do |mutation|
+              !mutation.type.equal?(:self)
+            end
+          end
           emit_right_mutations
         end
 

lib/mutant/mutator/node/return.rb

@@ -19,11 +19,11 @@ module Mutant
         # @api private
         #
         def dispatch
+          emit_singletons
           if value
             emit(value)
             emit_value_mutations
           end
-          emit_nil
         end
 
       end # Return

lib/mutant/mutator/node/send.rb

@@ -34,7 +34,7 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil
+          emit_singletons
           case selector
           when INDEX_REFERENCE
             run(Index::Reference)

lib/mutant/mutator/node/splat.rb

@@ -19,7 +19,7 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil
+          emit_singletons
           emit_expression_mutations
           emit(expression)
         end

lib/mutant/mutator/node/super.rb

@@ -21,13 +21,13 @@ module Mutant
         # @api private
         #
         def dispatch
+          emit_singletons
           emit(Z_SUPER)
           emit(EMPTY_SUPER)
           children.each_index do |index|
             mutate_child(index)
             delete_child(index)
           end
-          emit_nil
         end
 
       end # Super

lib/mutant/mutator/node/yield.rb

@@ -19,8 +19,8 @@ module Mutant
         #
         def dispatch
           super
+          emit_singletons
           children.each_index(&method(:delete_child))
-          emit_nil
         end
 
       end # Yield

lib/mutant/mutator/node/zsuper.rb

@@ -18,7 +18,7 @@ module Mutant
         # @api private
         #
         def dispatch
-          emit_nil
+          emit_singletons
         end
 
       end # ZSuper

lib/mutant/node_helpers.rb

@@ -30,6 +30,7 @@ module Mutant
     N_FALSE = s(:false)
     N_NIL   = s(:nil)
     N_EMPTY = s(:empty)
+    N_SELF  = s(:self)
 
     # Build a negated boolean node
     #

meta/and.rb

@@ -3,7 +3,7 @@
 Mutant::Meta::Example.add do
   source 'true and false'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'true'
   mutation 'false'
   mutation 'true or false'

meta/and_asgn.rb

@@ -3,10 +3,12 @@
 Mutant::Meta::Example.add do
   source 'a &&= 1'
 
+  singleton_mutations
+
   mutation 'a__mutant__ &&= 1'
   mutation 'a &&= nil'
   mutation 'a &&= 0'
   mutation 'a &&= -1'
   mutation 'a &&= 2'
-  mutation 'nil'
+  mutation 'a &&= self'
 end

meta/array.rb

@@ -3,7 +3,7 @@
 Mutant::Meta::Example.add do
   source '[true]'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'true'
   mutation '[false]'
   mutation '[nil]'
@@ -13,7 +13,7 @@ end
 Mutant::Meta::Example.add do
   source '[true, false]'
 
-  mutation 'nil'
+  singleton_mutations
 
   # Mutation of each element in array
   mutation '[nil, false]'

meta/block.rb

@@ -3,19 +3,22 @@
 Mutant::Meta::Example.add do
   source 'foo() { a; b }'
 
+  singleton_mutations
   mutation 'foo { a }'
   mutation 'foo { b }'
   mutation 'foo {}'
   mutation 'foo { raise }'
   mutation 'foo { a; nil }'
+  mutation 'foo { a; self }'
   mutation 'foo { nil; b }'
+  mutation 'foo { self; b }'
   mutation 'foo'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'foo { |a, b| }'
 
+  singleton_mutations
   mutation 'foo'
   mutation 'foo { |a, b| raise }'
   mutation 'foo { |a, b__mutant__| }'
@@ -23,13 +26,12 @@ Mutant::Meta::Example.add do
   mutation 'foo { |a| }'
   mutation 'foo { |b| }'
   mutation 'foo { || }'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'foo { |(a, b), c| }'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'foo { || }'
   mutation 'foo { |a, b, c| }'
   mutation 'foo { |(a, b), c| raise }'
@@ -46,10 +48,10 @@ end
 Mutant::Meta::Example.add do
   source 'foo { |(a)| }'
 
+  singleton_mutations
   mutation 'foo { || }'
   mutation 'foo { |a| }'
   mutation 'foo { |(a)| raise }'
   mutation 'foo { |(a__mutant__)| }'
   mutation 'foo'
-  mutation 'nil'
 end

meta/block_pass.rb

@@ -3,6 +3,6 @@
 Mutant::Meta::Example.add do
   source 'foo(&bar)'
 
+  singleton_mutations
   mutation 'foo'
-  mutation 'nil'
 end

meta/blockarg.rb

@@ -3,8 +3,8 @@
 Mutant::Meta::Example.add do
   source 'foo { |&bar| }'
 
+  singleton_mutations
   mutation 'foo { |&bar| raise }'
   mutation 'foo {}'
   mutation 'foo'
-  mutation 'nil'
 end

meta/break.rb

@@ -3,9 +3,9 @@
 Mutant::Meta::Example.add do
   source 'break true'
 
+  singleton_mutations
   mutation 'break false'
   mutation 'break nil'
   mutation 'break'
-  mutation 'nil'
   mutation 'next true'
 end

meta/case.rb

@@ -8,7 +8,7 @@ Mutant::Meta::Example.add do
     end
   RUBY
 
-  mutation 'nil'
+  singleton_mutations
 
   mutation <<-RUBY
     case
@@ -33,271 +33,192 @@ end
 
 Mutant::Meta::Example.add do
   source <<-RUBY
-    case :condition
+    case condition
-    when :foo
+    when A
-    when :bar, :baz
+    when B, C
-      :barbaz
+      C
     else
-      :else
+      D
     end
   RUBY
 
-  # Presence of branches
+  singleton_mutations
-  mutation <<-RUBY
-    case :condition
-    when :bar, :baz
-      :barbaz
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar, :baz
-      :barbaz
-    end
-  RUBY
 
-  # Mutations of condition
   mutation <<-RUBY
     case nil
-    when :foo
+    when A
-    when :bar, :baz
+    when B, C
-      :barbaz
+      C
     else
-      :else
+      D
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition__mutant__
-    when :foo
-    when :bar, :baz
-      :barbaz
-    else
-      :else
     end
   RUBY
 
-  # Mutations of branch bodies
   mutation <<-RUBY
-    case :condition
+    case self
-    when :foo
+    when A
+    when B, C
+      C
+    else
+      D
+    end
+  RUBY
+
+  mutation <<-RUBY
+    case condition
+    when A
       raise
-    when :bar, :baz
+    when B, C
-      :barbaz
+      C
     else
-      :else
+      D
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar, :baz
-      :barbaz__mutant__
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar, :baz
-      nil
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar, :baz
-      :barbaz
-    else
-      :else__mutant__
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar, :baz
-      :barbaz
-    else
-      nil
     end
   RUBY
 
-  # Mutations of when conditions
   mutation <<-RUBY
-    case :condition
+    case condition
-    when :foo__mutant__
-    when :bar, :baz
-      :barbaz
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
     when nil
-    when :bar, :baz
+    when B, C
-      :barbaz
+      C
     else
-      :else
+      D
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar__mutant__, :baz
-      :barbaz
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when nil, :baz
-      :barbaz
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar, nil
-      :barbaz
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar, :baz__mutant__
-      :barbaz
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :baz
-      :barbaz
-    else
-      :else
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when :foo
-    when :bar
-      :barbaz
-    else
-      :else
     end
   RUBY
 
-  mutation 'nil'
+  mutation <<-RUBY
-end
+    case condition
-
+    when self
-Mutant::Meta::Example.add do
+    when B, C
-  source <<-RUBY
+      C
-    case :condition
-    when :foo
-      :foo
     else
-      :else
+      D
     end
   RUBY
 
-  # Presence of branches
   mutation <<-RUBY
-    case :condition
+    case condition
-    when :foo
+    when B, C
-      :foo
+      C
-    end
-  RUBY
-
-  # Mutations of condition
-  mutation <<-RUBY
-    case nil
-    when :foo
-      :foo
     else
-      :else
+      D
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition__mutant__
-    when :foo
-      :foo
-    else
-      :else
     end
   RUBY
 
-  # Mutations of branch bodies
   mutation <<-RUBY
-    case :condition
+    case condition
-    when :foo
+    when A
+    when B, C
       nil
     else
-      :else
+      D
     end
   RUBY
+
   mutation <<-RUBY
-    case :condition
+    case condition
-    when :foo
+    when A
-      :foo__mutant__
+    when B, C
+      self
     else
-      :else
+      D
     end
   RUBY
+
   mutation <<-RUBY
-    case :condition
+    case condition
-    when :foo
+    when A
-      :foo
+    when C
+      C
     else
-      :else__mutant__
+      D
     end
   RUBY
+
   mutation <<-RUBY
-    case :condition
+    case condition
-    when :foo
+    when A
-      :foo
+    when nil, C
+      C
+    else
+      D
+    end
+  RUBY
+
+  mutation <<-RUBY
+    case condition
+    when A
+    when self, C
+      C
+    else
+      D
+    end
+  RUBY
+
+  mutation <<-RUBY
+    case condition
+    when A
+    when B
+      C
+    else
+      D
+    end
+  RUBY
+
+  mutation <<-RUBY
+    case condition
+    when A
+    when B, nil
+      C
+    else
+      D
+    end
+  RUBY
+
+  mutation <<-RUBY
+    case condition
+    when A
+    when B, self
+      C
+    else
+      D
+    end
+  RUBY
+
+  mutation <<-RUBY
+    case condition
+    when A
+    else
+      D
+    end
+  RUBY
+
+  mutation <<-RUBY
+    case condition
+    when A
+    when B, C
+      C
     else
       nil
     end
   RUBY
 
-  # Mutations of when conditions
   mutation <<-RUBY
-    case :condition
+    case condition
-    when :foo__mutant__
+    when A
-      :foo
+    when B, C
+      C
     else
-      :else
+      self
-    end
-  RUBY
-  mutation <<-RUBY
-    case :condition
-    when nil
-      :foo
-    else
-      :else
     end
   RUBY
 
-  mutation 'nil'
+  mutation <<-RUBY
+    case condition
+    when A
+    when B, C
+      C
     end
+  RUBY
+end
+
+

meta/cbase.rb

@@ -3,6 +3,6 @@
 Mutant::Meta::Example.add do
   source '::A'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'A'
 end

meta/const.rb

@@ -3,7 +3,7 @@
 Mutant::Meta::Example.add do
   source 'A::B::C'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'B::C'
   mutation 'C'
 end

meta/cvar.rb

@@ -3,5 +3,5 @@
 Mutant::Meta::Example.add do
   source '@@a'
 
-  mutation 'nil'
+  singleton_mutations
 end

meta/cvasgn.rb

@@ -3,8 +3,8 @@
 Mutant::Meta::Example.add do
   source '@@a = true'
 
+  singleton_mutations
   mutation '@@a__mutant__ = true'
   mutation '@@a = false'
   mutation '@@a = nil'
-  mutation 'nil'
 end

meta/def.rb

@@ -7,10 +7,11 @@ Mutant::Meta::Example.add do
 end
 
 Mutant::Meta::Example.add do
-  source "def foo\nfoo\nrescue\nend"
+  source 'def foo; foo; rescue; end'
 
   mutation 'def foo; raise; end'
   mutation 'def foo; nil; rescue; end'
+  mutation 'def foo; self; rescue; end'
   mutation 'def foo; end'
 end
 

meta/dstr.rb

@@ -3,8 +3,11 @@
 Mutant::Meta::Example.add do
   source '"foo#{bar}baz"'
 
-  mutation 'nil'
+  singleton_mutations
   mutation '"#{nil}#{bar}baz"'
+  mutation '"#{self}#{bar}baz"'
   mutation '"foo#{bar}#{nil}"'
+  mutation '"foo#{bar}#{self}"'
   mutation '"foo#{nil}baz"'
+  mutation '"foo#{self}baz"'
 end

meta/dsym.rb

@@ -1,11 +1,13 @@
 # encoding: utf-8
 
 Mutant::Meta::Example.add do
-
   source ':"foo#{bar}baz"'
 
+  singleton_mutations
   mutation ':"#{nil}#{bar}baz"'
+  mutation ':"#{self}#{bar}baz"'
   mutation ':"foo#{bar}#{nil}"'
+  mutation ':"foo#{bar}#{self}"'
   mutation ':"foo#{nil}baz"'
-  mutation 'nil'
+  mutation ':"foo#{self}baz"'
 end

meta/ensure.rb

@@ -3,7 +3,7 @@
 Mutant::Meta::Example.add do
   source 'begin; rescue; ensure; true; end'
 
+  singleton_mutations
   mutation 'begin; rescue; ensure; false; end'
   mutation 'begin; rescue; ensure; nil; end'
-  mutation 'nil'
 end

meta/false.rb

@@ -0,0 +1,8 @@
+# encoding: utf-8
+
+Mutant::Meta::Example.add do
+  source 'false'
+
+  mutation 'nil'
+  mutation 'true'
+end

meta/float.rb

@@ -3,8 +3,7 @@
 Mutant::Meta::Example.add do
   source '10.0'
 
-  # generic
+  singleton_mutations
-  mutation 'nil'
 
   # edge cases
   mutation '0.0'
@@ -20,7 +19,7 @@ end
 Mutant::Meta::Example.add do
   source '0.0'
 
-  mutation 'nil'
+  singleton_mutations
   mutation '1.0'
   mutation '(0.0 / 0.0)'
   mutation '(1.0 / 0.0)'
@@ -30,7 +29,7 @@ end
 Mutant::Meta::Example.add do
   source '-0.0'
 
-  mutation 'nil'
+  singleton_mutations
   mutation '1.0'
   mutation '(0.0 / 0.0)'
   mutation '(1.0 / 0.0)'

meta/gvar.rb

@@ -3,5 +3,5 @@
 Mutant::Meta::Example.add do
   source '$a'
 
-  mutation 'nil'
+  singleton_mutations
 end

meta/gvasgn.rb

@@ -3,8 +3,8 @@
 Mutant::Meta::Example.add do
   source '$a = true'
 
+  singleton_mutations
   mutation '$a__mutant__ = true'
   mutation '$a = false'
   mutation '$a = nil'
-  mutation 'nil'
 end

meta/hash.rb

@@ -3,8 +3,7 @@
 Mutant::Meta::Example.add do
   source '{true => true, false => false}'
 
-  # Literal replaced with nil
+  singleton_mutations
-  mutation 'nil'
 
   # Mutation of each key and value in hash
   mutation '{ false => true  ,  false => false }'

meta/if.rb

@@ -1,57 +1,55 @@
 # encoding: utf-8
 
 Mutant::Meta::Example.add do
-  source 'if :condition; true; else false; end'
+  source 'if condition; true; else false; end'
+
+  singleton_mutations
 
   # mutation of condition
-  mutation 'if :condition__mutant__; true; else false; end'
+  mutation 'if !condition; true; else false; end'
-  mutation 'if !:condition;          true; else false; end'
   mutation 'if nil;        true; else false; end'
   mutation 'if true;       true; else false; end'
   mutation 'if false;      true; else false; end'
 
   # Deleted else branch
-  mutation 'if :condition; true end'
+  mutation 'if condition; true end'
 
   # Deleted if branch resuting in unless rendering
-  mutation 'unless :condition; false; end'
+  mutation 'unless condition; false; end'
 
   # Deleted if branch with promoting else branch to if branch
-  mutation 'if :condition; false end'
+  mutation 'if condition; false end'
 
   # mutation of if body
-  mutation 'if :condition; false; else false; end'
+  mutation 'if condition; false; else false; end'
-  mutation 'if :condition; nil;   else false; end'
+  mutation 'if condition; nil;   else false; end'
 
   # mutation of else body
-  mutation 'if :condition; true;  else true;  end'
+  mutation 'if condition; true;  else true;  end'
-  mutation 'if :condition; true;  else nil;   end'
+  mutation 'if condition; true;  else nil;   end'
-
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'if condition; true; end'
 
+  singleton_mutations
   mutation 'if !condition; true;  end'
   mutation 'if condition;  false; end'
   mutation 'if condition;  nil;   end'
   mutation 'if true;       true;  end'
   mutation 'if false;      true;  end'
   mutation 'if nil;        true;  end'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
-  source 'unless :condition; true; end'
+  source 'unless condition; true; end'
 
-  mutation 'unless !:condition;          true;  end'
+  singleton_mutations
-  mutation 'unless :condition__mutant__; true;  end'
+  mutation 'unless !condition; true;  end'
   mutation 'unless nil;        true;  end'
-  mutation 'unless :condition;           false; end'
-  mutation 'unless :condition;           nil;   end'
   mutation 'unless true;       true;  end'
   mutation 'unless false;      true;  end'
-  mutation 'if     :condition;           true;  end'
+  mutation 'unless condition;  false; end'
-  mutation 'nil'
+  mutation 'unless condition;  nil;   end'
+  mutation 'if     condition;  true;  end'
 end

meta/int.rb

@@ -3,8 +3,7 @@
 Mutant::Meta::Example.add do
   source '10'
 
-  # generic
+  singleton_mutations
-  mutation 'nil'
 
   # edge cases
   mutation '0'

meta/ivasgn.rb

@@ -3,8 +3,8 @@
 Mutant::Meta::Example.add do
   source '@a = true'
 
+  singleton_mutations
   mutation '@a__mutant__ = true'
   mutation '@a = false'
   mutation '@a = nil'
-  mutation 'nil'
 end

meta/kwbegin.rb

@@ -3,7 +3,7 @@
 Mutant::Meta::Example.add do
   source 'begin; true; end'
 
+  singleton_mutations
   mutation 'begin; false; end'
   mutation 'begin; nil; end'
-  mutation 'nil'
 end

meta/lvar.rb

@@ -4,11 +4,13 @@ Mutant::Meta::Example.add do
   source 'a = nil; a'
 
   mutation 'a = nil; nil'
+  mutation 'a = nil; self'
   mutation 'a = nil'
   # TODO: fix invalid AST
   #   These ASTs are not valid and should NOT be emitted
   #   Mutations of lvarasgn need to be special cased to avoid this.
   mutation s(:begin, s(:lvasgn, :a__mutant__, s(:nil)), s(:lvar, :a))
   mutation s(:begin, s(:nil), s(:lvar, :a))
+  mutation s(:begin, s(:self), s(:lvar, :a))
   mutation s(:lvar, :a)
 end

meta/lvasgn.rb

@@ -3,8 +3,8 @@
 Mutant::Meta::Example.add do
   source 'a = true'
 
+  singleton_mutations
   mutation 'a__mutant__ = true'
   mutation 'a = false'
   mutation 'a = nil'
-  mutation 'nil'
 end

meta/masgn.rb

@@ -3,5 +3,5 @@
 Mutant::Meta::Example.add do
   source 'a, b = c, d'
 
-  mutation 'nil'
+  singleton_mutations
 end

meta/match_current_line.rb

@@ -3,6 +3,7 @@
 Mutant::Meta::Example.add do
   source 'true if /foo/'
 
+  singleton_mutations
   mutation 'false if /foo/'
   mutation 'true if //'
   mutation 'nil if /foo/'
@@ -10,5 +11,4 @@ Mutant::Meta::Example.add do
   mutation 'true if false'
   mutation 'true if nil'
   mutation 'true if /a\A/'
-  mutation 'nil'
 end

meta/next.rb

@@ -3,9 +3,9 @@
 Mutant::Meta::Example.add do
   source 'next true'
 
+  singleton_mutations
   mutation 'next false'
   mutation 'next nil'
   mutation 'next'
-  mutation 'nil'
   mutation 'break true'
 end

meta/op_assgn.rb

@@ -3,12 +3,14 @@
 Mutant::Meta::Example.add do
   source '@a.b += 1'
 
+  singleton_mutations
   mutation '@a.b += -1'
   mutation '@a.b += 2'
   mutation '@a.b += 0'
   mutation '@a.b += nil'
+  mutation '@a.b += self'
   mutation 'nil.b += 1'
-  mutation 'nil'
+  mutation 'self.b += 1'
   # TODO: fix invalid AST
   #   This should not get emitted as invalid AST with valid unparsed source
   mutation s(:op_asgn, s(:ivar, :@a), :+, s(:int, 1))

meta/or.rb

@@ -3,7 +3,7 @@
 Mutant::Meta::Example.add do
   source 'true or false'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'true'
   mutation 'false'
   mutation 'true and false'

meta/or_asgn.rb

@@ -3,20 +3,22 @@
 Mutant::Meta::Example.add do
   source 'a ||= 1'
 
+  singleton_mutations
   mutation 'a__mutant__ ||= 1'
   mutation 'a ||= nil'
+  mutation 'a ||= self'
   mutation 'a ||= 0'
   mutation 'a ||= -1'
   mutation 'a ||= 2'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source '@a ||= 1'
 
+  singleton_mutations
   mutation '@a ||= nil'
+  mutation '@a ||= self'
   mutation '@a ||= 0'
   mutation '@a ||= -1'
   mutation '@a ||= 2'
-  mutation 'nil'
 end

meta/range.rb

@@ -3,7 +3,7 @@
 Mutant::Meta::Example.add do
   source '1..100'
 
-  mutation 'nil'
+  singleton_mutations
   mutation '1...100'
   mutation '(0.0 / 0.0)..100'
   mutation '1..(1.0 / 0.0)'
@@ -12,7 +12,9 @@ Mutant::Meta::Example.add do
   mutation '0..100'
   mutation '2..100'
   mutation 'nil..100'
+  mutation 'self..100'
   mutation '1..nil'
+  mutation '1..self'
   mutation '1..0'
   mutation '1..1'
   mutation '1..99'
@@ -23,7 +25,7 @@ end
 Mutant::Meta::Example.add do
   source '1...100'
 
-  mutation 'nil'
+  singleton_mutations
   mutation '1..100'
   mutation '(0.0 / 0.0)...100'
   mutation '1...(1.0 / 0.0)'
@@ -32,7 +34,9 @@ Mutant::Meta::Example.add do
   mutation '0...100'
   mutation '2...100'
   mutation 'nil...100'
+  mutation 'self...100'
   mutation '1...nil'
+  mutation '1...self'
   mutation '1...0'
   mutation '1...1'
   mutation '1...99'

meta/regex.rb

@@ -3,18 +3,20 @@
 Mutant::Meta::Example.add do
   source '/foo/'
 
+  singleton_mutations
   mutation '//'    # match all
   mutation '/a\A/' # match nothing
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source '/#{foo.bar}n/'
 
+  singleton_mutations
   mutation '//' # match all
   mutation '/#{foo}n/'
   mutation '/a\A/'         # match nothing
   mutation '/#{nil.bar}n/'
+  mutation '/#{self.bar}n/'
   mutation '/#{nil}n/'
-  mutation 'nil'
+  mutation '/#{self}n/'
 end

meta/rescue.rb

@@ -3,8 +3,10 @@
 Mutant::Meta::Example.add do
   source 'begin; rescue ExceptionA, ExceptionB => error; true; end'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'begin; rescue ExceptionA, ExceptionB; true; end'
+  mutation 'begin; rescue self, ExceptionB => error; true; end'
+  mutation 'begin; rescue ExceptionA, self => error; true; end'
   mutation 'begin; rescue ExceptionA, ExceptionB => error; false; end'
   mutation 'begin; rescue ExceptionA, ExceptionB => error; nil; end'
   mutation 'begin; rescue ExceptionA => error; true; end'
@@ -14,16 +16,17 @@ end
 Mutant::Meta::Example.add do
   source 'begin; rescue SomeException => error; true; end'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'begin; rescue SomeException; true; end'
   mutation 'begin; rescue SomeException => error; false; end'
   mutation 'begin; rescue SomeException => error; nil; end'
+  mutation 'begin; rescue self => error; true; end'
 end
 
 Mutant::Meta::Example.add do
   source 'begin; rescue => error; true end'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'begin; rescue => error; false; end'
   mutation 'begin; rescue => error; nil; end'
   mutation 'begin; rescue; true; end'
@@ -32,7 +35,7 @@ end
 Mutant::Meta::Example.add do
   source 'begin; rescue; true end'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'begin; rescue; false; end'
   mutation 'begin; rescue; nil; end'
 end

meta/restarg.rb

@@ -3,9 +3,11 @@
 Mutant::Meta::Example.add do
   source 'foo(*bar)'
 
+  singleton_mutations
   mutation 'foo'
   mutation 'foo(nil)'
+  mutation 'foo(self)'
+  mutation 'foo(*self)'
   mutation 'foo(bar)'
   mutation 'foo(*nil)'
-  mutation 'nil'
 end

meta/return.rb

@@ -3,13 +3,14 @@
 Mutant::Meta::Example.add do
   source 'return'
 
-  mutation 'nil'
+  singleton_mutations
 end
 
 Mutant::Meta::Example.add do
   source 'return foo'
 
+  singleton_mutations
   mutation 'foo'
   mutation 'return nil'
-  mutation 'nil'
+  mutation 'return self'
 end

meta/send.rb

@@ -3,14 +3,14 @@
 Mutant::Meta::Example.add do
   source 'reverse_each'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'each'
 end
 
 Mutant::Meta::Example.add do
   source 'reverse_map'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'map'
   mutation 'each'
 end
@@ -18,18 +18,20 @@ end
 Mutant::Meta::Example.add do
   source 'map'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'each'
 end
 
 Mutant::Meta::Example.add do
   source 'foo == bar'
 
+  singleton_mutations
   mutation 'foo'
   mutation 'bar'
   mutation 'nil == bar'
+  mutation 'self == bar'
   mutation 'foo == nil'
-  mutation 'nil'
+  mutation 'foo == self'
   mutation 'foo.eql?(bar)'
   mutation 'foo.equal?(bar)'
 end
@@ -37,43 +39,40 @@ end
 Mutant::Meta::Example.add do
   source 'foo.gsub(a, b)'
 
+  singleton_mutations
   mutation 'foo'
   mutation 'foo.gsub(a)'
   mutation 'foo.gsub(b)'
   mutation 'foo.gsub'
   mutation 'foo.sub(a, b)'
   mutation 'foo.gsub(a, nil)'
+  mutation 'foo.gsub(a, self)'
   mutation 'foo.gsub(nil, b)'
+  mutation 'foo.gsub(self, b)'
   mutation 'nil.gsub(a, b)'
-  mutation 'nil'
+  mutation 'self.gsub(a, b)'
 end
 
 Mutant::Meta::Example.add do
   source 'foo.send(bar)'
 
+  singleton_mutations
   mutation 'foo.send'
   mutation 'foo.public_send(bar)'
   mutation 'bar'
   mutation 'foo'
+  mutation 'self.send(bar)'
   mutation 'foo.send(nil)'
+  mutation 'foo.send(self)'
   mutation 'nil.send(bar)'
-  mutation 'nil'
-end
-
-Mutant::Meta::Example.add do
-  source 'self.foo ||= expression'
-
-  mutation 'self.foo ||= nil'
-  mutation 'nil.foo ||= expression'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'self.bar = baz'
 
-  mutation 'nil'
+  singleton_mutations
   mutation 'self.bar = nil'
-  mutation 'self'
+  mutation 'self.bar = self'
   mutation 'self.bar'
   mutation 'baz'
   # This one could probably be removed
@@ -83,9 +82,11 @@ end
 Mutant::Meta::Example.add do
   source 'foo.bar = baz'
 
+  singleton_mutations
   mutation 'foo'
-  mutation 'nil'
   mutation 'foo.bar = nil'
+  mutation 'foo.bar = self'
+  mutation 'self.bar = baz'
   mutation 'foo.bar'
   mutation 'baz'
   # This one could probably be removed
@@ -95,91 +96,91 @@ end
 Mutant::Meta::Example.add do
   source 'foo[bar]=baz'
 
+  singleton_mutations
   mutation 'foo'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'foo(*bar)'
 
+  singleton_mutations
   mutation 'foo'
   mutation 'foo(nil)'
   mutation 'foo(bar)'
+  mutation 'foo(self)'
   mutation 'foo(*nil)'
-  mutation 'nil'
+  mutation 'foo(*self)'
 end
 
 Mutant::Meta::Example.add do
   source 'foo(&bar)'
 
+  singleton_mutations
   mutation 'foo'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'foo[*bar]'
 
+  singleton_mutations
   mutation 'foo'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'foo'
 
-  mutation 'nil'
+  singleton_mutations
 end
 
 Mutant::Meta::Example.add do
   source 'self.foo'
 
+  singleton_mutations
   mutation 'foo'
-  mutation 'self'
   mutation 'nil.foo'
-  mutation 'nil'
 end
 
 Unparser::Constants::KEYWORDS.each do |keyword|
   Mutant::Meta::Example.add do
     source "self.#{keyword}"
 
+    singleton_mutations
     mutation "nil.#{keyword}"
-    mutation 'nil'
-    mutation 'self'
   end
 end
 
 Mutant::Meta::Example.add do
   source 'foo.bar'
 
+  singleton_mutations
   mutation 'foo'
   mutation 'nil.bar'
-  mutation 'nil'
+  mutation 'self.bar'
 end
 
 Mutant::Meta::Example.add do
   source 'self.class.foo'
 
+  singleton_mutations
   mutation 'self.class'
   mutation 'self.foo'
   mutation 'nil.class.foo'
   mutation 'nil.foo'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'foo(nil)'
 
+  singleton_mutations
   mutation 'foo'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'self.foo(nil)'
 
-  mutation 'self'
+  singleton_mutations
   mutation 'self.foo'
   mutation 'foo(nil)'
-  mutation 'nil'
   mutation 'nil.foo(nil)'
 end
 
@@ -187,54 +188,50 @@ Unparser::Constants::KEYWORDS.each do |keyword|
   Mutant::Meta::Example.add do
     source "foo.#{keyword}(nil)"
 
+    singleton_mutations
+    mutation "self.#{keyword}(nil)"
     mutation "foo.#{keyword}"
     mutation 'foo'
     mutation "nil.#{keyword}(nil)"
-    mutation 'nil'
   end
 end
 
 Mutant::Meta::Example.add do
   source 'foo(nil, nil)'
 
+  singleton_mutations
   mutation 'foo()'
   mutation 'foo(nil)'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source '(left - right) / foo'
 
+  singleton_mutations
   mutation 'foo'
   mutation '(left - right)'
   mutation 'left / foo'
   mutation 'right / foo'
   mutation '(left - right) / nil'
+  mutation '(left - right) / self'
   mutation '(left - nil) / foo'
+  mutation '(left - self) / foo'
   mutation '(nil - right) / foo'
+  mutation '(self - right) / foo'
   mutation 'nil / foo'
-  mutation 'nil'
+  mutation 'self / foo'
 end
 
 (Mutant::BINARY_METHOD_OPERATORS - [:==, :eql?]).each do |operator|
   Mutant::Meta::Example.add do
     source "true #{operator} false"
 
+    singleton_mutations
+    mutation 'true'
+    mutation 'false'
     mutation "false #{operator} false"
     mutation "nil   #{operator} false"
     mutation "true  #{operator} true"
     mutation "true  #{operator} nil"
-    mutation 'true'
-    mutation 'false'
-    mutation 'nil'
-  end
-
-  Mutant::Meta::Example.add do
-    source "left #{operator} right"
-    mutation 'left'
-    mutation 'right'
-    mutation "left #{operator} nil"
-    mutation "nil #{operator} right"
-    mutation 'nil'
   end
 end

meta/str.rb

@@ -3,5 +3,5 @@
 Mutant::Meta::Example.add do
   source '"foo"'
 
-  mutation 'nil'
+  singleton_mutations
 end

meta/super.rb

@@ -3,24 +3,27 @@
 Mutant::Meta::Example.add do
   source 'super'
 
-  mutation 'nil'
+  singleton_mutations
 end
 
 Mutant::Meta::Example.add do
   source 'super()'
 
+  singleton_mutations
+  # this is zsuper a totally differend node thant super()
   mutation 'super'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'super(foo, bar)'
 
+  singleton_mutations
   mutation 'super'
   mutation 'super()'
   mutation 'super(foo)'
   mutation 'super(bar)'
   mutation 'super(foo, nil)'
+  mutation 'super(foo, self)'
   mutation 'super(nil, bar)'
-  mutation 'nil'
+  mutation 'super(self, bar)'
 end

meta/symbol.rb

@@ -3,6 +3,6 @@
 Mutant::Meta::Example.add do
   source ':foo'
 
-  mutation 'nil'
+  singleton_mutations
   mutation ':foo__mutant__'
 end

meta/true.rb

@@ -0,0 +1,8 @@
+# encoding: utf-8
+
+Mutant::Meta::Example.add do
+  source 'true'
+
+  mutation 'nil'
+  mutation 'false'
+end

meta/unless.rb

@@ -1,15 +0,0 @@
-# encoding: utf-8
-
-Mutant::Meta::Example.add do
-  source 'until true; foo; bar; end'
-
-  mutation 'until true; bar; end'
-  mutation 'until true; foo; end'
-  mutation 'until true; end'
-  mutation 'until false; foo; bar; end'
-  mutation 'until nil;   foo; bar; end'
-  mutation 'until true;  foo; nil; end'
-  mutation 'until true;  nil; bar; end'
-  mutation 'until true;  raise; end'
-  mutation 'nil'
-end

meta/until.rb

@@ -0,0 +1,17 @@
+# encoding: utf-8
+
+Mutant::Meta::Example.add do
+  source 'until true; foo; bar; end'
+
+  singleton_mutations
+  mutation 'until true; bar; end'
+  mutation 'until true; foo; end'
+  mutation 'until true; end'
+  mutation 'until false; foo; bar; end'
+  mutation 'until nil; foo; bar; end'
+  mutation 'until true; foo; nil; end'
+  mutation 'until true; foo; self; end'
+  mutation 'until true; nil; bar; end'
+  mutation 'until true; self; bar; end'
+  mutation 'until true; raise; end'
+end

meta/while.rb

@@ -3,6 +3,9 @@
 Mutant::Meta::Example.add do
   source 'while true; foo; bar; end'
 
+  singleton_mutations
+  mutation 'while true; self; bar; end'
+  mutation 'while true; foo; self; end'
   mutation 'while true; bar; end'
   mutation 'while true; foo; end'
   mutation 'while true; end'
@@ -11,14 +14,13 @@ Mutant::Meta::Example.add do
   mutation 'while true;  foo; nil; end'
   mutation 'while true;  nil; bar; end'
   mutation 'while true;  raise; end'
-  mutation 'nil'
 end
 
 Mutant::Meta::Example.add do
   source 'while true; end'
 
+  singleton_mutations
   mutation 'while true; raise; end'
   mutation 'while false; end'
   mutation 'while nil; end'
-  mutation 'nil'
 end

meta/yield.rb

@@ -3,8 +3,8 @@
 Mutant::Meta::Example.add do
   source 'yield true'
 
+  singleton_mutations
   mutation 'yield false'
   mutation 'yield nil'
   mutation 'yield'
-  mutation 'nil'
 end