diff --git a/lib/mutant/constants.rb b/lib/mutant/constants.rb
index e515e635..d8433c3e 100644
--- a/lib/mutant/constants.rb
+++ b/lib/mutant/constants.rb
@@ -64,7 +64,6 @@ module Mutant
   OPERATOR_METHODS =
     OPERATOR_EXPANSIONS.keys + INDEX_OPERATORS + UNARY_METHOD_OPERATORS
 
-
   # Hopefully all types parser does generate
   NODE_TYPES = [
     :lvasgn, :ivasgn, :cvasgn, :gvasgn,
diff --git a/spec/unit/mutant/cli/class_methods/new_spec.rb b/spec/unit/mutant/cli/class_methods/new_spec.rb
index c0c2cc1f..28207094 100644
--- a/spec/unit/mutant/cli/class_methods/new_spec.rb
+++ b/spec/unit/mutant/cli/class_methods/new_spec.rb
@@ -24,7 +24,7 @@ describe Mutant::CLI, '.new' do
   let(:time)   { Time.now        }
 
   before do
-    Time.stub(:now => time)
+    Time.stub(now: time)
   end
 
   # Defaults
diff --git a/spec/unit/mutant/cli/class_methods/run_spec.rb b/spec/unit/mutant/cli/class_methods/run_spec.rb
index 506c8b22..0ac8bd10 100644
--- a/spec/unit/mutant/cli/class_methods/run_spec.rb
+++ b/spec/unit/mutant/cli/class_methods/run_spec.rb
@@ -5,16 +5,16 @@ require 'spec_helper'
 describe Mutant::CLI, '.run' do
   subject { object.run(argv) }
 
-  let(:object)     { described_class                                 }
-  let(:argv)       { double('ARGV')                                  }
-  let(:attributes) { double('Options')                               }
-  let(:runner)     { double('Runner', :success? => success)          }
-  let(:config)     { double('Config')                                }
-  let(:instance)   { double(described_class.name, :config => config) }
+  let(:object)     { described_class                              }
+  let(:argv)       { double('ARGV')                               }
+  let(:attributes) { double('Options')                            }
+  let(:runner)     { double('Runner', success?: success)          }
+  let(:config)     { double('Config')                             }
+  let(:instance)   { double(described_class.name, config: config) }
 
   before do
-    described_class.stub(:new => instance)
-    Mutant::Runner::Config.stub(:run => runner)
+    described_class.stub(new: instance)
+    Mutant::Runner::Config.stub(run: runner)
   end
 
   context 'when runner is successful' do
diff --git a/spec/unit/mutant/killer/rspec/class_methods/new_spec.rb b/spec/unit/mutant/killer/rspec/class_methods/new_spec.rb
index c15f0e6a..964c497e 100644
--- a/spec/unit/mutant/killer/rspec/class_methods/new_spec.rb
+++ b/spec/unit/mutant/killer/rspec/class_methods/new_spec.rb
@@ -18,24 +18,24 @@ describe Mutant::Killer::Rspec, '.new' do
   let(:mutation) do
     double(
       'Mutation',
-      :subject => mutation_subject,
-      :should_survive? => false
+      subject: mutation_subject,
+      should_survive?: false
     )
   end
 
   let(:strategy) do
     double(
       'Strategy',
-      :spec_files => ['foo'],
-      :error_stream => $stderr,
-      :output_stream => $stdout
+      spec_files: ['foo'],
+      error_stream: $stderr,
+      output_stream: $stdout
     )
   end
 
   before do
     mutation.stub(:insert)
     mutation.stub(:reset)
-    RSpec::Core::Runner.stub(:run => exit_status)
+    RSpec::Core::Runner.stub(run: exit_status)
   end
 
   context 'when run exits zero' do
diff --git a/spec/unit/mutant/killer/success_predicate_spec.rb b/spec/unit/mutant/killer/success_predicate_spec.rb
index 605d81ea..d9c748ea 100644
--- a/spec/unit/mutant/killer/success_predicate_spec.rb
+++ b/spec/unit/mutant/killer/success_predicate_spec.rb
@@ -5,13 +5,13 @@ require 'spec_helper'
 describe Mutant::Killer, '#success?' do
   subject { object.success? }
 
-  let(:object)           { class_under_test.new(strategy, mutation)    }
-  let(:strategy)         { double('Strategy')                          }
-  let(:mutation)         { double('Mutation', :success? => kill_state) }
-  let(:kill_state)       { double('Kill State')                        }
+  let(:object)           { class_under_test.new(strategy, mutation) }
+  let(:strategy)         { double('Strategy')                       }
+  let(:mutation)         { double('Mutation', success?: kill_state) }
+  let(:kill_state)       { double('Kill State')                     }
 
   before do
-    kill_state.stub(:freeze => kill_state, :dup => kill_state)
+    kill_state.stub(freeze: kill_state, dup: kill_state)
   end
 
   let(:class_under_test) do
diff --git a/spec/unit/mutant/loader/eval/class_methods/run_spec.rb b/spec/unit/mutant/loader/eval/class_methods/run_spec.rb
index 1ddb6966..aeb51866 100644
--- a/spec/unit/mutant/loader/eval/class_methods/run_spec.rb
+++ b/spec/unit/mutant/loader/eval/class_methods/run_spec.rb
@@ -11,7 +11,7 @@ describe Mutant::Loader::Eval, '.run' do
   let(:line)   { 1               }
 
   let(:mutation_subject) do
-    double('Subject', :source_path => path, :source_line => line)
+    double('Subject', source_path: path, source_line: line)
   end
 
   let(:source) do
diff --git a/spec/unit/mutant/matcher/namespace/each_spec.rb b/spec/unit/mutant/matcher/namespace/each_spec.rb
index d8110cbe..8891db1e 100644
--- a/spec/unit/mutant/matcher/namespace/each_spec.rb
+++ b/spec/unit/mutant/matcher/namespace/each_spec.rb
@@ -10,10 +10,10 @@ describe Mutant::Matcher::Namespace, '#each' do
 
   let(:cache) { Mutant::Cache.new }
 
-  let(:singleton_a) { double('SingletonA', :name => 'TestApp::Literal') }
-  let(:singleton_b) { double('SingletonB', :name => 'TestApp::Foo')     }
-  let(:subject_a)   { double('SubjectA')                                }
-  let(:subject_b)   { double('SubjectB')                                }
+  let(:singleton_a) { double('SingletonA', name: 'TestApp::Literal') }
+  let(:singleton_b) { double('SingletonB', name: 'TestApp::Foo')     }
+  let(:subject_a)   { double('SubjectA')                             }
+  let(:subject_b)   { double('SubjectB')                             }
 
   before do
     Mutant::Matcher::Methods::Singleton.stub(:each)
@@ -22,7 +22,7 @@ describe Mutant::Matcher::Namespace, '#each' do
     Mutant::Matcher::Methods::Instance.stub(:each)
       .with(cache, singleton_a)
       .and_yield(subject_b)
-    ObjectSpace.stub(:each_object => [singleton_a, singleton_b])
+    ObjectSpace.stub(each_object: [singleton_a, singleton_b])
   end
 
   context 'with no block' do
diff --git a/spec/unit/mutant/mutator/each_spec.rb b/spec/unit/mutant/mutator/each_spec.rb
index db64797e..94712f6e 100644
--- a/spec/unit/mutant/mutator/each_spec.rb
+++ b/spec/unit/mutant/mutator/each_spec.rb
@@ -19,7 +19,7 @@ describe Mutant::Mutator, '.each' do
     end
 
     before do
-      Mutant::Random.stub(:hex_string => random_string)
+      Mutant::Random.stub(hex_string: random_string)
     end
 
     it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/and_asgn/mutation_spec.rb b/spec/unit/mutant/mutator/node/and_asgn/mutation_spec.rb
index b9eb2390..54adc364 100644
--- a/spec/unit/mutant/mutator/node/and_asgn/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/and_asgn/mutation_spec.rb
@@ -20,7 +20,7 @@ describe Mutant::Mutator::Node::OpAsgn, 'and_asgn' do
   end
 
   before do
-    Mutant::Random.stub(:fixnum => random_fixnum, :hex_string => random_string)
+    Mutant::Random.stub(fixnum: random_fixnum, hex_string: random_string)
   end
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/block/mutation_spec.rb b/spec/unit/mutant/mutator/node/block/mutation_spec.rb
index 2c48dd9e..e133cf89 100644
--- a/spec/unit/mutant/mutator/node/block/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/block/mutation_spec.rb
@@ -26,7 +26,7 @@ describe Mutant::Mutator, 'block' do
     let(:source) { 'foo { |a, b| }' }
 
     before do
-      Mutant::Random.stub(:hex_string => 'random')
+      Mutant::Random.stub(hex_string: 'random')
     end
 
     let(:mutations) do
@@ -47,7 +47,7 @@ describe Mutant::Mutator, 'block' do
   context 'with block pattern args' do
 
     before do
-      Mutant::Random.stub(:hex_string => 'random')
+      Mutant::Random.stub(hex_string: 'random')
     end
 
     let(:source) { 'foo { |(a, b), c| }' }
diff --git a/spec/unit/mutant/mutator/node/case/mutation_spec.rb b/spec/unit/mutant/mutator/node/case/mutation_spec.rb
index 6a96c3bf..2d534668 100644
--- a/spec/unit/mutant/mutator/node/case/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/case/mutation_spec.rb
@@ -6,7 +6,7 @@ describe Mutant::Mutator::Node::Case do
   let(:random_string) { 'random' }
 
   before do
-    Mutant::Random.stub(:hex_string => random_string)
+    Mutant::Random.stub(hex_string: random_string)
   end
 
   context 'with multiple when branches' do
diff --git a/spec/unit/mutant/mutator/node/define/mutation_spec.rb b/spec/unit/mutant/mutator/node/define/mutation_spec.rb
index ac3de669..2720e3c0 100644
--- a/spec/unit/mutant/mutator/node/define/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/define/mutation_spec.rb
@@ -43,7 +43,7 @@ describe Mutant::Mutator, 'def' do
     let(:source) { 'def foo(a, b); end' }
 
     before do
-      Mutant::Random.stub(:hex_string => 'random')
+      Mutant::Random.stub(hex_string: 'random')
     end
 
     let(:mutations) do
@@ -83,7 +83,7 @@ describe Mutant::Mutator, 'def' do
     let(:source) { 'def foo(a = true); end' }
 
     before do
-      Mutant::Random.stub(:hex_string => 'random')
+      Mutant::Random.stub(hex_string: 'random')
     end
 
     let(:mutations) do
@@ -127,7 +127,7 @@ describe Mutant::Mutator, 'def' do
   context 'define on singleton with argument' do
 
     before do
-      Mutant::Random.stub(:hex_string => 'random')
+      Mutant::Random.stub(hex_string: 'random')
     end
 
     let(:source) { 'def self.foo(a, b); end' }
diff --git a/spec/unit/mutant/mutator/node/dstr/mutation_spec.rb b/spec/unit/mutant/mutator/node/dstr/mutation_spec.rb
index f1d29016..b47665c2 100644
--- a/spec/unit/mutant/mutator/node/dstr/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/dstr/mutation_spec.rb
@@ -4,7 +4,7 @@ require 'spec_helper'
 
 describe Mutant::Mutator::Node::Dstr, 'dstr' do
   before do
-    Mutant::Random.stub(:hex_string => 'random')
+    Mutant::Random.stub(hex_string: 'random')
   end
 
   let(:source)  { '"foo#{bar}baz"' }
diff --git a/spec/unit/mutant/mutator/node/dsym/mutation_spec.rb b/spec/unit/mutant/mutator/node/dsym/mutation_spec.rb
index 1fe8f35a..4c17306b 100644
--- a/spec/unit/mutant/mutator/node/dsym/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/dsym/mutation_spec.rb
@@ -4,7 +4,7 @@ require 'spec_helper'
 
 describe Mutant::Mutator::Node::Generic, 'dsum' do
   before do
-    Mutant::Random.stub(:hex_string => 'random')
+    Mutant::Random.stub(hex_string: 'random')
   end
 
   let(:source)  { ':"foo#{bar}baz"' }
diff --git a/spec/unit/mutant/mutator/node/if/mutation_spec.rb b/spec/unit/mutant/mutator/node/if/mutation_spec.rb
index 34585732..8a466af0 100644
--- a/spec/unit/mutant/mutator/node/if/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/if/mutation_spec.rb
@@ -4,7 +4,7 @@ require 'spec_helper'
 
 describe Mutant::Mutator, 'if' do
   before do
-    Mutant::Random.stub(:hex_string => 'random')
+    Mutant::Random.stub(hex_string: 'random')
   end
 
   context 'with if and else branches' do
diff --git a/spec/unit/mutant/mutator/node/literal/fixnum_spec.rb b/spec/unit/mutant/mutator/node/literal/fixnum_spec.rb
index 795fc6d0..c0d134e8 100644
--- a/spec/unit/mutant/mutator/node/literal/fixnum_spec.rb
+++ b/spec/unit/mutant/mutator/node/literal/fixnum_spec.rb
@@ -12,7 +12,7 @@ describe Mutant::Mutator::Node::Literal, 'fixnum' do
   end
 
   before do
-    Mutant::Random.stub(:fixnum => random_fixnum)
+    Mutant::Random.stub(fixnum: random_fixnum)
   end
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/literal/float_spec.rb b/spec/unit/mutant/mutator/node/literal/float_spec.rb
index 4332cca8..2b9f0d04 100644
--- a/spec/unit/mutant/mutator/node/literal/float_spec.rb
+++ b/spec/unit/mutant/mutator/node/literal/float_spec.rb
@@ -20,7 +20,7 @@ describe Mutant::Mutator::Node::Literal, 'float' do
   let(:random_float) { 7.123 }
 
   before do
-    Mutant::Random.stub(:float => random_float)
+    Mutant::Random.stub(float: random_float)
   end
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/literal/range_spec.rb b/spec/unit/mutant/mutator/node/literal/range_spec.rb
index 360d447f..33f8c1df 100644
--- a/spec/unit/mutant/mutator/node/literal/range_spec.rb
+++ b/spec/unit/mutant/mutator/node/literal/range_spec.rb
@@ -5,7 +5,7 @@ require 'spec_helper'
 describe Mutant::Mutator::Node::Literal, 'range' do
 
   before :each do
-    Mutant::Random.stub(:fixnum => random_fixnum)
+    Mutant::Random.stub(fixnum: random_fixnum)
   end
 
   let(:random_fixnum) { 5 }
diff --git a/spec/unit/mutant/mutator/node/literal/string_spec.rb b/spec/unit/mutant/mutator/node/literal/string_spec.rb
index b2fe6473..e11cb780 100644
--- a/spec/unit/mutant/mutator/node/literal/string_spec.rb
+++ b/spec/unit/mutant/mutator/node/literal/string_spec.rb
@@ -12,7 +12,7 @@ describe Mutant::Mutator::Node::Literal, 'string' do
   end
 
   before do
-    Mutant::Random.stub(:hex_string => random_string)
+    Mutant::Random.stub(hex_string: random_string)
   end
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/literal/symbol_spec.rb b/spec/unit/mutant/mutator/node/literal/symbol_spec.rb
index 0acc656f..f4ee7874 100644
--- a/spec/unit/mutant/mutator/node/literal/symbol_spec.rb
+++ b/spec/unit/mutant/mutator/node/literal/symbol_spec.rb
@@ -12,7 +12,7 @@ describe Mutant::Mutator::Node::Literal, 'symbol' do
   end
 
   before do
-    Mutant::Random.stub(:hex_string => random_string)
+    Mutant::Random.stub(hex_string: random_string)
   end
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/named_value/access/mutation_spec.rb b/spec/unit/mutant/mutator/node/named_value/access/mutation_spec.rb
index 18c9cc77..3b3a0fb8 100644
--- a/spec/unit/mutant/mutator/node/named_value/access/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/named_value/access/mutation_spec.rb
@@ -4,7 +4,7 @@ require 'spec_helper'
 
 describe Mutant::Mutator::Node::NamedValue::Access, 'mutations' do
   before do
-    Mutant::Random.stub(:hex_string => 'random')
+    Mutant::Random.stub(hex_string: 'random')
   end
 
   context 'global variable' do
diff --git a/spec/unit/mutant/mutator/node/named_value/constant_assignment/mutation_spec.rb b/spec/unit/mutant/mutator/node/named_value/constant_assignment/mutation_spec.rb
index ceefe8c5..97aecc04 100644
--- a/spec/unit/mutant/mutator/node/named_value/constant_assignment/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/named_value/constant_assignment/mutation_spec.rb
@@ -4,7 +4,7 @@ require 'spec_helper'
 
 describe Mutant::Mutator::Node::NamedValue::VariableAssignment, 'mutations' do
   before do
-    Mutant::Random.stub(:hex_string => 'random')
+    Mutant::Random.stub(hex_string: 'random')
   end
 
   let(:source) { 'A = true' }
diff --git a/spec/unit/mutant/mutator/node/named_value/variable_assignment/mutation_spec.rb b/spec/unit/mutant/mutator/node/named_value/variable_assignment/mutation_spec.rb
index ebeed93b..044b989a 100644
--- a/spec/unit/mutant/mutator/node/named_value/variable_assignment/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/named_value/variable_assignment/mutation_spec.rb
@@ -4,7 +4,7 @@ require 'spec_helper'
 
 describe Mutant::Mutator::Node::NamedValue::VariableAssignment, 'mutations' do
   before do
-    Mutant::Random.stub(:hex_string => 'random')
+    Mutant::Random.stub(hex_string: 'random')
   end
 
   context 'global variable' do
diff --git a/spec/unit/mutant/mutator/node/op_assgn/mutation_spec.rb b/spec/unit/mutant/mutator/node/op_assgn/mutation_spec.rb
index 6f0429d1..017c5087 100644
--- a/spec/unit/mutant/mutator/node/op_assgn/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/op_assgn/mutation_spec.rb
@@ -20,7 +20,7 @@ describe Mutant::Mutator::Node::Generic, 'op_asgn' do
   end
 
   before do
-    Mutant::Random.stub(:fixnum => random_fixnum)
+    Mutant::Random.stub(fixnum: random_fixnum)
   end
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/or_asgn/mutation_spec.rb b/spec/unit/mutant/mutator/node/or_asgn/mutation_spec.rb
index 063bf6df..051daa08 100644
--- a/spec/unit/mutant/mutator/node/or_asgn/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/or_asgn/mutation_spec.rb
@@ -20,7 +20,7 @@ describe Mutant::Mutator::Node::OpAsgn, 'or_asgn' do
   end
 
   before do
-    Mutant::Random.stub(:fixnum => random_fixnum, :hex_string => random_string)
+    Mutant::Random.stub(fixnum: random_fixnum, hex_string: random_string)
   end
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/mutator/node/rescue/mutation_spec.rb b/spec/unit/mutant/mutator/node/rescue/mutation_spec.rb
index e59338c3..25fbf5fd 100644
--- a/spec/unit/mutant/mutator/node/rescue/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/rescue/mutation_spec.rb
@@ -15,7 +15,7 @@ describe Mutant::Mutator::Node::Generic, 'rescue' do
   end
 
   before do
-    Mutant::Random.stub(:hex_string => 'random')
+    Mutant::Random.stub(hex_string: 'random')
   end
 
   pending do
diff --git a/spec/unit/mutant/predicate_spec.rb b/spec/unit/mutant/predicate_spec.rb
index 487ba557..a69d60dc 100644
--- a/spec/unit/mutant/predicate_spec.rb
+++ b/spec/unit/mutant/predicate_spec.rb
@@ -1,8 +1,8 @@
 require 'spec_helper'
 
 filter_helpers = proc do
-  let(:input_a) { double('Input A', :foo => 'bar') }
-  let(:input_b) { double('Input B', :foo => 'baz') }
+  let(:input_a) { double('Input A', foo: 'bar') }
+  let(:input_b) { double('Input B', foo: 'baz') }
 
   let(:filter_a) do
     input_a = self.input_a
diff --git a/spec/unit/mutant/runner/config/subjects_spec.rb b/spec/unit/mutant/runner/config/subjects_spec.rb
index f70cc19f..fc7abe07 100644
--- a/spec/unit/mutant/runner/config/subjects_spec.rb
+++ b/spec/unit/mutant/runner/config/subjects_spec.rb
@@ -10,24 +10,24 @@ describe Mutant::Runner::Config, '#subjects' do
   let(:config) do
     double(
       'Config',
-      :class    => Mutant::Config,
-      :subjects => [subject_a, subject_b],
-      :strategy => strategy,
-      :reporter => reporter
+      class:    Mutant::Config,
+      subjects: [subject_a, subject_b],
+      strategy: strategy,
+      reporter: reporter
     )
   end
 
-  let(:reporter)  { double('Reporter')                   }
-  let(:strategy)  { double('Strategy')                   }
-  let(:subject_a) { double('Subject A')                  }
-  let(:subject_b) { double('Subject B')                  }
-  let(:runner_a)  { double('Runner A', :stop? => stop_a) }
-  let(:runner_b)  { double('Runner B', :stop? => stop_b) }
+  let(:reporter)  { double('Reporter')                }
+  let(:strategy)  { double('Strategy')                }
+  let(:subject_a) { double('Subject A')               }
+  let(:subject_b) { double('Subject B')               }
+  let(:runner_a)  { double('Runner A', stop?: stop_a) }
+  let(:runner_b)  { double('Runner B', stop?: stop_b) }
 
   before do
     strategy.stub(:setup)
     strategy.stub(:teardown)
-    reporter.stub(:report => reporter)
+    reporter.stub(report: reporter)
     Mutant::Runner.stub(:run).with(config, subject_a).and_return(runner_a)
     Mutant::Runner.stub(:run).with(config, subject_b).and_return(runner_b)
   end
diff --git a/spec/unit/mutant/runner/config/success_predicate_spec.rb b/spec/unit/mutant/runner/config/success_predicate_spec.rb
index 3d1df834..6df24e44 100644
--- a/spec/unit/mutant/runner/config/success_predicate_spec.rb
+++ b/spec/unit/mutant/runner/config/success_predicate_spec.rb
@@ -10,9 +10,9 @@ describe Mutant::Runner::Config, '#success?' do
   let(:config) do
     double(
       'Config',
-      :reporter => reporter,
-      :strategy => strategy,
-      :subjects => [subject_a, subject_b]
+      reporter: reporter,
+      strategy: strategy,
+      subjects: [subject_a, subject_b]
     )
   end
 
@@ -22,15 +22,15 @@ describe Mutant::Runner::Config, '#success?' do
   let(:subject_b) { double('Subject B') }
 
   let(:runner_a) do
-    double('Runner A', :stop? => stop_a, :success? => success_a)
+    double('Runner A', stop?: stop_a, success?: success_a)
   end
 
   let(:runner_b) do
-    double('Runner B', :stop? => stop_b, :success? => success_b)
+    double('Runner B', stop?: stop_b, success?: success_b)
   end
 
   before do
-    reporter.stub(:report => reporter)
+    reporter.stub(report: reporter)
     strategy.stub(:setup)
     strategy.stub(:teardown)
     Mutant::Runner.stub(:run).with(config, subject_a).and_return(runner_a)
diff --git a/spec/unit/mutant/runner/mutation/killer_spec.rb b/spec/unit/mutant/runner/mutation/killer_spec.rb
index e7e0da13..9a402bd0 100644
--- a/spec/unit/mutant/runner/mutation/killer_spec.rb
+++ b/spec/unit/mutant/runner/mutation/killer_spec.rb
@@ -8,24 +8,24 @@ describe Mutant::Runner::Mutation, '#killer' do
   let(:config) do
     double(
       'Config',
-      :fail_fast => fail_fast,
-      :reporter  => reporter,
-      :strategy  => strategy
+      fail_fast: fail_fast,
+      reporter:  reporter,
+      strategy:  strategy
     )
   end
 
-  let(:reporter)  { double('Reporter')                             }
-  let(:mutation)  { double('Mutation', :class => Mutant::Mutation) }
-  let(:strategy)  { double('Strategy')                             }
-  let(:killer)    { double('Killer', :success? => success)         }
-  let(:fail_fast) { false                                          }
-  let(:success)   { false                                          }
+  let(:reporter)  { double('Reporter')                          }
+  let(:mutation)  { double('Mutation', class: Mutant::Mutation) }
+  let(:strategy)  { double('Strategy')                          }
+  let(:killer)    { double('Killer', success?: success)         }
+  let(:fail_fast) { false                                       }
+  let(:success)   { false                                       }
 
   subject { object.killer }
 
   before do
-    reporter.stub(:report => reporter)
-    strategy.stub(:kill => killer)
+    reporter.stub(report: reporter)
+    strategy.stub(kill: killer)
   end
 
   it 'should call configuration to identify strategy' do
diff --git a/spec/unit/mutant/runner/subject/success_predicate_spec.rb b/spec/unit/mutant/runner/subject/success_predicate_spec.rb
index b0bbd55d..5baf1ba6 100644
--- a/spec/unit/mutant/runner/subject/success_predicate_spec.rb
+++ b/spec/unit/mutant/runner/subject/success_predicate_spec.rb
@@ -10,26 +10,26 @@ describe Mutant::Runner::Subject, '#success?' do
   let(:mutation_subject) do
     double(
       'Subject',
-      :class     => Mutant::Subject,
-      :mutations => [mutation_a, mutation_b]
+      class:     Mutant::Subject,
+      mutations: [mutation_a, mutation_b]
     )
   end
 
-  let(:reporter)   { double('Reporter')                      }
-  let(:config)     { double('Config', :reporter => reporter) }
-  let(:mutation_a) { double('Mutation A')                    }
-  let(:mutation_b) { double('Mutation B')                    }
+  let(:reporter)   { double('Reporter')                   }
+  let(:config)     { double('Config', reporter: reporter) }
+  let(:mutation_a) { double('Mutation A')                 }
+  let(:mutation_b) { double('Mutation B')                 }
 
   let(:runner_a) do
-    double('Runner A', :success? => success_a, :stop? => stop_a)
+    double('Runner A', success?: success_a, stop?: stop_a)
   end
 
   let(:runner_b) do
-    double('Runner B', :success? => success_b, :stop? => stop_b)
+    double('Runner B', success?: success_b, stop?: stop_b)
   end
 
   before do
-    reporter.stub(:report => reporter)
+    reporter.stub(report: reporter)
     Mutant::Runner.stub(:run).with(config, mutation_a).and_return(runner_a)
     Mutant::Runner.stub(:run).with(config, mutation_b).and_return(runner_b)
   end
diff --git a/test_app/spec/shared/method_filter_parse_behavior.rb b/test_app/spec/shared/method_filter_parse_behavior.rb
index 0cddb85d..62268c4d 100644
--- a/test_app/spec/shared/method_filter_parse_behavior.rb
+++ b/test_app/spec/shared/method_filter_parse_behavior.rb
@@ -2,7 +2,7 @@
 
 shared_examples_for 'a method filter parse result' do
   before do
-    expected_class.stub(:new => response)
+    expected_class.stub(new: response)
   end
 
   let(:response) { double('Response') }