Add /static\z/ -> #end_with? mutations

- Adds the following mutations:
  * `a.match(/text\z/)` -> `b.end_with?('text')`
  * `a.match?(/text\z/)` -> `b.end_with?('text')`
  * `a =~ /text\z/` -> `b.end_with?('text')`

Changelog.md

@@ -6,6 +6,10 @@
       * `a.match(/\Atext/)` -> `b.start_with?('text')`
       * `a.match?(/\Atext/)` -> `b.start_with?('text')`
       * `a =~ /\Atext/` -> `b.start_with?('text')`
+    * Add `/static\z/` -> `#end_with?` mutations:
+      * `a.match(/text\z/)` -> `b.end_with?('text')`
+      * `a.match?(/text\z/)` -> `b.end_with?('text')`
+      * `a =~ /text\z/` -> `b.end_with?('text')`
 
 # v0.10.25 2021-01-02-03
 

lib/mutant/mutator/node/send.rb

@@ -51,7 +51,9 @@ class Send < self
           }
         )
 
-        REGEXP_MATCH_METHODS = %i[=~ match match?].freeze
+        REGEXP_MATCH_METHODS    = %i[=~ match match?].freeze
+        REGEXP_START_WITH_NODES = %i[regexp_bos_anchor regexp_literal_literal].freeze
+        REGEXP_END_WITH_NODES   = %i[regexp_literal_literal regexp_eos_anchor].freeze
 
       private
 
@@ -86,7 +88,7 @@ def normal_dispatch
         end
 
         def emit_selector_specific_mutations
-          emit_start_with_mutation
+          emit_start_end_with_mutations
           emit_predicate_mutations
           emit_array_mutation
           emit_static_send
@@ -97,9 +99,8 @@ def emit_selector_specific_mutations
           emit_lambda_mutation
         end
 
-        def emit_start_with_mutation
-          return unless REGEXP_MATCH_METHODS.include?(selector)
-          return unless arguments.one?
+        def emit_start_end_with_mutations # rubocop:disable Metrics/CyclomaticComplexity, Metrics/MethodLength
+          return unless REGEXP_MATCH_METHODS.include?(selector) && arguments.one?
 
           argument = Mutant::Util.one(arguments)
 
@@ -109,11 +110,22 @@ def emit_start_with_mutation
 
           regexp_children = regexp_ast.children
 
-          return unless regexp_children.map(&:type).eql?(%i[regexp_bos_anchor regexp_literal_literal])
+          case regexp_children.map(&:type)
+          when REGEXP_START_WITH_NODES
+            emit_start_with(regexp_children)
+          when REGEXP_END_WITH_NODES
+            emit_end_with(regexp_children)
+          end
+        end
 
-          literal = Mutant::Util.one(regexp_children.last.children)
+        def emit_start_with(regexp_nodes)
+          literal = Mutant::Util.one(regexp_nodes.last.children)
+          emit_type(receiver, :start_with?, s(:str, literal))
+        end
 
-          emit(s(:send, receiver, :start_with?, s(:str, literal)))
+        def emit_end_with(regexp_nodes)
+          literal = Mutant::Util.one(regexp_nodes.first.children)
+          emit_type(receiver, :end_with?, s(:str, literal))
         end
 
         def emit_predicate_mutations

meta/send.rb

@@ -811,3 +811,18 @@
   mutation 'foo(//)'
   mutation 'foo(/nomatch\A/)'
 end
+
+Mutant::Meta::Example.add :send do
+  source 'a.match(/foo\z/)'
+
+  singleton_mutations
+
+  mutation 'a.match?(/foo\z/)'
+  mutation 'a.match'
+  mutation 'a'
+  mutation '/foo\z/'
+  mutation 'a.match(//)'
+  mutation 'a.match(/nomatch\A/)'
+  mutation 'self.match(/foo\z/)'
+  mutation "a.end_with?('foo')"
+end