Upgrade to Ruby 2.5

.circleci/config.yml

@@ -4,20 +4,14 @@ defaults: &defaults
     - checkout
     - run: bundle install
     - run: bundle exec rake ci
-
 version: 2
 jobs:
-  ruby_2_3:
+  ruby_2_5:
     <<: *defaults
     docker:
-      - image: circleci/ruby:2.3.4
-  ruby_2_4:
-    <<: *defaults
-    docker:
-      - image: circleci/ruby:2.4.1
+      - image: circleci/ruby:2.5.3
 workflows:
   version: 2
   test:
     jobs:
-      - ruby_2_3
-      - ruby_2_4
+      - ruby_2_5

.rubocop.yml

@@ -4,4 +4,4 @@ AllCops:
     - 'test_app/**/*'
     - 'tmp/**/*'
     - 'vendor/**/*'
-  TargetRubyVersion: 2.3
+  TargetRubyVersion: 2.5

lib/mutant/expression/namespace.rb

@@ -44,7 +44,7 @@ module Mutant
         #
         # @return [Integer]
         def match_length(expression)
-          if @recursion_pattern =~ expression.syntax
+          if @recursion_pattern.match?(expression.syntax)
             scope_name.length
           else
             0

lib/mutant/warning_filter.rb

@@ -36,7 +36,7 @@ module Mutant
     #
     # @return [self]
     def write(message)
-      if WARNING_PATTERN =~ message
+      if WARNING_PATTERN.match?(message)
         warnings << message
       else
         target.write(message)

mutant.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |gem|
   gem.extra_rdoc_files = %w[LICENSE]
   gem.executables      = %w[mutant]
 
-  gem.required_ruby_version = '>= 2.3'
+  gem.required_ruby_version = '>= 2.5'
 
   gem.add_runtime_dependency('abstract_type', '~> 0.0.7')
   gem.add_runtime_dependency('adamantium',    '~> 0.2.0')