diff --git a/.rspec b/.rspec
index 2ac79342..58e12543 100644
--- a/.rspec
+++ b/.rspec
@@ -1,4 +1,5 @@
 --color
+--require spec_helper
 --format progress
 --warnings
 --order random
diff --git a/spec/integration/mutant/corpus_spec.rb b/spec/integration/mutant/corpus_spec.rb
index 07330654..e7215507 100644
--- a/spec/integration/mutant/corpus_spec.rb
+++ b/spec/integration/mutant/corpus_spec.rb
@@ -1,9 +1,4 @@
-# encoding: UTF-8
-
-require 'parallel'
-require 'spec_helper'
-
-describe 'Mutant on ruby corpus' do
+RSpec.describe 'Mutant on ruby corpus' do
 
   before do
     skip 'Corpus test is deactivated on 1.9.3' if RUBY_VERSION.eql?('1.9.3')
diff --git a/spec/integration/mutant/null_spec.rb b/spec/integration/mutant/null_spec.rb
index 1882c6f9..6cd6735e 100644
--- a/spec/integration/mutant/null_spec.rb
+++ b/spec/integration/mutant/null_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe 'null integration' do
+RSpec.describe 'null integration' do
 
   let(:base_cmd) { 'bundle exec mutant -I lib --require test_app "TestApp*"' }
 
diff --git a/spec/integration/mutant/rspec_spec.rb b/spec/integration/mutant/rspec_spec.rb
index 5e707ba8..a77582f8 100644
--- a/spec/integration/mutant/rspec_spec.rb
+++ b/spec/integration/mutant/rspec_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe 'rspec integration' do
+RSpec.describe 'rspec integration' do
 
   let(:base_cmd) { 'bundle exec mutant -I lib --require test_app --use rspec' }
 
diff --git a/spec/integration/mutant/test_mutator_handles_types_spec.rb b/spec/integration/mutant/test_mutator_handles_types_spec.rb
index e18f4093..be5eb57a 100644
--- a/spec/integration/mutant/test_mutator_handles_types_spec.rb
+++ b/spec/integration/mutant/test_mutator_handles_types_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe do
+RSpec.describe do
 
   specify 'mutant should not crash for any node parser can generate' do
     Mutant::AST::Types::ALL.each do |type|
diff --git a/spec/integration/mutant/zombie_spec.rb b/spec/integration/mutant/zombie_spec.rb
index da6ead57..ae90fe3d 100644
--- a/spec/integration/mutant/zombie_spec.rb
+++ b/spec/integration/mutant/zombie_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe 'as a zombie' do
+RSpec.describe 'as a zombie' do
   specify 'it allows to create zombie from mutant' do
     expect { Mutant.zombify }.to change { defined?(Zombie) }.from(nil).to('constant')
     expect(Zombie.constants).to include(:Mutant)
diff --git a/spec/shared/method_matcher_behavior.rb b/spec/shared/method_matcher_behavior.rb
index af10c5e3..1a76919d 100644
--- a/spec/shared/method_matcher_behavior.rb
+++ b/spec/shared/method_matcher_behavior.rb
@@ -1,4 +1,4 @@
-shared_examples_for 'a method matcher' do
+RSpec.shared_examples_for 'a method matcher' do
 
   before { subject }
 
diff --git a/spec/shared/mutator_behavior.rb b/spec/shared/mutator_behavior.rb
index 97ae66d2..cdb3ee9e 100644
--- a/spec/shared/mutator_behavior.rb
+++ b/spec/shared/mutator_behavior.rb
@@ -1,6 +1,6 @@
 # encoding: UTF-8
 
-shared_examples_for 'a mutator' do
+RSpec.shared_examples_for 'a mutator' do
   subject { object.each(node, &yields.method(:<<)) }
 
   let(:yields) { []              }
@@ -48,7 +48,7 @@ shared_examples_for 'a mutator' do
   end
 end
 
-shared_examples_for 'a noop mutator' do
+RSpec.shared_examples_for 'a noop mutator' do
   let(:mutations) { [] }
 
   it_should_behave_like 'a mutator'
diff --git a/spec/unit/mutant/cli_spec.rb b/spec/unit/mutant/cli_spec.rb
index ae8dec4d..acfa953b 100644
--- a/spec/unit/mutant/cli_spec.rb
+++ b/spec/unit/mutant/cli_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-shared_examples_for 'an invalid cli run' do
+RSpec.shared_examples_for 'an invalid cli run' do
   it 'raises error' do
     expect do
       subject
@@ -8,13 +6,13 @@ shared_examples_for 'an invalid cli run' do
   end
 end
 
-shared_examples_for 'a cli parser' do
+RSpec.shared_examples_for 'a cli parser' do
   it { expect(subject.config.integration).to eql(expected_integration)       }
   it { expect(subject.config.reporter).to eql(expected_reporter)             }
   it { expect(subject.config.matcher_config).to eql(expected_matcher_config) }
 end
 
-describe Mutant::CLI do
+RSpec.describe Mutant::CLI do
   let(:object) { described_class }
 
   describe '.run' do
diff --git a/spec/unit/mutant/context/root_spec.rb b/spec/unit/mutant/context/root_spec.rb
index f1b3d4b6..45e81a24 100644
--- a/spec/unit/mutant/context/root_spec.rb
+++ b/spec/unit/mutant/context/root_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Context, '#root' do
+RSpec.describe Mutant::Context, '#root' do
   subject { object.root }
 
   let(:object) { described_class.allocate }
diff --git a/spec/unit/mutant/context/scope/root_spec.rb b/spec/unit/mutant/context/scope/root_spec.rb
index 82931e0d..74fbbe58 100644
--- a/spec/unit/mutant/context/scope/root_spec.rb
+++ b/spec/unit/mutant/context/scope/root_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Context::Scope, '#root' do
+RSpec.describe Mutant::Context::Scope, '#root' do
   subject { object.root(node) }
 
   let(:object) { described_class.new(TestApp::Literal, path) }
diff --git a/spec/unit/mutant/context/scope/unqualified_name_spec.rb b/spec/unit/mutant/context/scope/unqualified_name_spec.rb
index b06f6baa..da413fe7 100644
--- a/spec/unit/mutant/context/scope/unqualified_name_spec.rb
+++ b/spec/unit/mutant/context/scope/unqualified_name_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Context::Scope, '#unqualified_name' do
+RSpec.describe Mutant::Context::Scope, '#unqualified_name' do
   subject { object.unqualified_name }
 
   let(:path)   { double('Path') }
diff --git a/spec/unit/mutant/diff_spec.rb b/spec/unit/mutant/diff_spec.rb
index 2dbe9a72..617fbea3 100644
--- a/spec/unit/mutant/diff_spec.rb
+++ b/spec/unit/mutant/diff_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Diff do
+RSpec.describe Mutant::Diff do
   let(:object) { described_class }
 
   describe '.build' do
diff --git a/spec/unit/mutant/expression/method_spec.rb b/spec/unit/mutant/expression/method_spec.rb
index 3b53f6f4..295fc323 100644
--- a/spec/unit/mutant/expression/method_spec.rb
+++ b/spec/unit/mutant/expression/method_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Expression::Method do
+RSpec.describe Mutant::Expression::Method do
 
   let(:object)           { described_class.parse(input) }
   let(:env)              { Fixtures::TEST_ENV           }
diff --git a/spec/unit/mutant/expression/methods_spec.rb b/spec/unit/mutant/expression/methods_spec.rb
index 761fc0f8..857c8337 100644
--- a/spec/unit/mutant/expression/methods_spec.rb
+++ b/spec/unit/mutant/expression/methods_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Expression::Methods do
+RSpec.describe Mutant::Expression::Methods do
 
   let(:object)            { described_class.parse(input) }
   let(:env)               { Fixtures::TEST_ENV           }
diff --git a/spec/unit/mutant/expression/namespace/flat_spec.rb b/spec/unit/mutant/expression/namespace/flat_spec.rb
index ebb70c6c..8e9d0723 100644
--- a/spec/unit/mutant/expression/namespace/flat_spec.rb
+++ b/spec/unit/mutant/expression/namespace/flat_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Expression::Namespace::Exact do
+RSpec.describe Mutant::Expression::Namespace::Exact do
 
   let(:object) { described_class.parse(input) }
   let(:env)    { Fixtures::TEST_ENV           }
diff --git a/spec/unit/mutant/expression/namespace/recursive_spec.rb b/spec/unit/mutant/expression/namespace/recursive_spec.rb
index 5b97ecd1..fc8e1408 100644
--- a/spec/unit/mutant/expression/namespace/recursive_spec.rb
+++ b/spec/unit/mutant/expression/namespace/recursive_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Expression::Namespace::Recursive do
+RSpec.describe Mutant::Expression::Namespace::Recursive do
 
   let(:object) { described_class.parse(input) }
   let(:input)  { 'TestApp::Literal*'          }
diff --git a/spec/unit/mutant/expression_spec.rb b/spec/unit/mutant/expression_spec.rb
index 31a1a6ef..7f4f5db6 100644
--- a/spec/unit/mutant/expression_spec.rb
+++ b/spec/unit/mutant/expression_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Expression do
+RSpec.describe Mutant::Expression do
   let(:object) { described_class }
 
   describe '.try_parse' do
diff --git a/spec/unit/mutant/integration_spec.rb b/spec/unit/mutant/integration_spec.rb
index faa4fa33..35365637 100644
--- a/spec/unit/mutant/integration_spec.rb
+++ b/spec/unit/mutant/integration_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Integration do
+RSpec.describe Mutant::Integration do
 
   let(:class_under_test) do
     Class.new(described_class)
@@ -14,7 +12,7 @@ describe Mutant::Integration do
   end
 end
 
-describe Mutant::Integration::Null do
+RSpec.describe Mutant::Integration::Null do
 
   let(:object) { described_class.new }
 
diff --git a/spec/unit/mutant/isolation_spec.rb b/spec/unit/mutant/isolation_spec.rb
index 5a99e4da..7c004d75 100644
--- a/spec/unit/mutant/isolation_spec.rb
+++ b/spec/unit/mutant/isolation_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Isolation::None do
+RSpec.describe Mutant::Isolation::None do
   before do
     @initial = 1
   end
@@ -24,7 +22,7 @@ describe Mutant::Isolation::None do
   end
 end
 
-describe Mutant::Isolation::Fork do
+RSpec.describe Mutant::Isolation::Fork do
   before do
     @initial = 1
   end
diff --git a/spec/unit/mutant/loader/eval_spec.rb b/spec/unit/mutant/loader/eval_spec.rb
index 9d729940..2570b433 100644
--- a/spec/unit/mutant/loader/eval_spec.rb
+++ b/spec/unit/mutant/loader/eval_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Loader::Eval, '.call' do
+RSpec.describe Mutant::Loader::Eval, '.call' do
 
   subject { object.call(node, mutation_subject) }
 
diff --git a/spec/unit/mutant/matcher/chain_spec.rb b/spec/unit/mutant/matcher/chain_spec.rb
index 1d3756a3..f5273a18 100644
--- a/spec/unit/mutant/matcher/chain_spec.rb
+++ b/spec/unit/mutant/matcher/chain_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Chain do
+RSpec.describe Mutant::Matcher::Chain do
 
   let(:object) { described_class.new(matchers) }
 
diff --git a/spec/unit/mutant/matcher/compiler/subject_prefix_spec.rb b/spec/unit/mutant/matcher/compiler/subject_prefix_spec.rb
index a9aec9dc..cfa891e6 100644
--- a/spec/unit/mutant/matcher/compiler/subject_prefix_spec.rb
+++ b/spec/unit/mutant/matcher/compiler/subject_prefix_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Compiler::SubjectPrefix do
+RSpec.describe Mutant::Matcher::Compiler::SubjectPrefix do
   let(:object) { described_class.new(Mutant::Expression.parse('Foo*')) }
 
   let(:_subject) { double('Subject', expression: Mutant::Expression.parse(subject_expression)) }
diff --git a/spec/unit/mutant/matcher/compiler_spec.rb b/spec/unit/mutant/matcher/compiler_spec.rb
index 5e696971..97cf910b 100644
--- a/spec/unit/mutant/matcher/compiler_spec.rb
+++ b/spec/unit/mutant/matcher/compiler_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Compiler do
+RSpec.describe Mutant::Matcher::Compiler do
   let(:object) { described_class }
 
   let(:env) { Fixtures::TEST_ENV }
diff --git a/spec/unit/mutant/matcher/filter_spec.rb b/spec/unit/mutant/matcher/filter_spec.rb
index 2d12cad6..8f6ee7f6 100644
--- a/spec/unit/mutant/matcher/filter_spec.rb
+++ b/spec/unit/mutant/matcher/filter_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Filter do
+RSpec.describe Mutant::Matcher::Filter do
   let(:object) { described_class.new(matcher, predicate) }
 
   describe '#each' do
diff --git a/spec/unit/mutant/matcher/method/instance_spec.rb b/spec/unit/mutant/matcher/method/instance_spec.rb
index af7e7ec5..c26e2434 100644
--- a/spec/unit/mutant/matcher/method/instance_spec.rb
+++ b/spec/unit/mutant/matcher/method/instance_spec.rb
@@ -1,7 +1,5 @@
-require 'spec_helper'
-
 # rubocop:disable ClassAndModuleChildren
-describe Mutant::Matcher::Method::Instance do
+RSpec.describe Mutant::Matcher::Method::Instance do
 
   let(:env)      { Fixtures::TEST_ENV             }
   let(:reporter) { Fixtures::TEST_CONFIG.reporter }
diff --git a/spec/unit/mutant/matcher/method/singleton_spec.rb b/spec/unit/mutant/matcher/method/singleton_spec.rb
index 54d3e7ed..64d21969 100644
--- a/spec/unit/mutant/matcher/method/singleton_spec.rb
+++ b/spec/unit/mutant/matcher/method/singleton_spec.rb
@@ -1,7 +1,5 @@
-require 'spec_helper'
-
 # rubocop:disable ClassAndModuleChildren
-describe Mutant::Matcher::Method::Singleton, '#each' do
+RSpec.describe Mutant::Matcher::Method::Singleton, '#each' do
   subject { object.each { |subject| yields << subject } }
 
   let(:object)       { described_class.new(env, scope, method) }
diff --git a/spec/unit/mutant/matcher/methods/instance_spec.rb b/spec/unit/mutant/matcher/methods/instance_spec.rb
index e198ea52..9a0f3ffd 100644
--- a/spec/unit/mutant/matcher/methods/instance_spec.rb
+++ b/spec/unit/mutant/matcher/methods/instance_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Methods::Instance, '#each' do
+RSpec.describe Mutant::Matcher::Methods::Instance, '#each' do
   let(:object) { described_class.new(env, Foo) }
   let(:env)    { Fixtures::TEST_ENV            }
 
diff --git a/spec/unit/mutant/matcher/methods/singleton_spec.rb b/spec/unit/mutant/matcher/methods/singleton_spec.rb
index eaddef5f..d1809607 100644
--- a/spec/unit/mutant/matcher/methods/singleton_spec.rb
+++ b/spec/unit/mutant/matcher/methods/singleton_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Methods::Singleton, '#each' do
+RSpec.describe Mutant::Matcher::Methods::Singleton, '#each' do
   let(:object) { described_class.new(env, Foo) }
   let(:env)    { Fixtures::TEST_ENV            }
 
diff --git a/spec/unit/mutant/matcher/namespace_spec.rb b/spec/unit/mutant/matcher/namespace_spec.rb
index b61e5d88..fee55dc0 100644
--- a/spec/unit/mutant/matcher/namespace_spec.rb
+++ b/spec/unit/mutant/matcher/namespace_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Namespace do
+RSpec.describe Mutant::Matcher::Namespace do
   let(:object) { described_class.new(env, Mutant::Expression.parse('TestApp*')) }
   let(:yields) { []                                                             }
   let(:env)    { double('Env')                                                  }
diff --git a/spec/unit/mutant/matcher/null_spec.rb b/spec/unit/mutant/matcher/null_spec.rb
index b37c16f7..48a8dfa5 100644
--- a/spec/unit/mutant/matcher/null_spec.rb
+++ b/spec/unit/mutant/matcher/null_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Matcher::Null do
+RSpec.describe Mutant::Matcher::Null do
   let(:object) { described_class.new }
 
   describe '#each' do
diff --git a/spec/unit/mutant/mutation_spec.rb b/spec/unit/mutant/mutation_spec.rb
index 09886e08..a1ba70f2 100644
--- a/spec/unit/mutant/mutation_spec.rb
+++ b/spec/unit/mutant/mutation_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Mutation do
+RSpec.describe Mutant::Mutation do
 
   class TestMutation < Mutant::Mutation
     SYMBOL = 'test'.freeze
diff --git a/spec/unit/mutant/mutator/node_spec.rb b/spec/unit/mutant/mutator/node_spec.rb
index 3b56aa7d..06f281a5 100644
--- a/spec/unit/mutant/mutator/node_spec.rb
+++ b/spec/unit/mutant/mutator/node_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Mutator::Node do
+RSpec.describe Mutant::Mutator::Node do
   Mutant::Meta::Example::ALL.each do |example|
     context "on #{example.node.type.inspect}" do
       it 'generates the correct mutations' do
diff --git a/spec/unit/mutant/reporter/cli_spec.rb b/spec/unit/mutant/reporter/cli_spec.rb
index 177797c7..0e46393f 100644
--- a/spec/unit/mutant/reporter/cli_spec.rb
+++ b/spec/unit/mutant/reporter/cli_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Reporter::CLI do
+RSpec.describe Mutant::Reporter::CLI do
   let(:object) { described_class.new(output) }
   let(:output) { StringIO.new }
 
diff --git a/spec/unit/mutant/reporter/null_spec.rb b/spec/unit/mutant/reporter/null_spec.rb
index 7f7655c2..025ef05a 100644
--- a/spec/unit/mutant/reporter/null_spec.rb
+++ b/spec/unit/mutant/reporter/null_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Reporter::Null do
+RSpec.describe Mutant::Reporter::Null do
   let(:object) { described_class.new }
 
   describe '#report' do
diff --git a/spec/unit/mutant/require_highjack_spec.rb b/spec/unit/mutant/require_highjack_spec.rb
index e9288327..a54dadc4 100644
--- a/spec/unit/mutant/require_highjack_spec.rb
+++ b/spec/unit/mutant/require_highjack_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::RequireHighjack do
+RSpec.describe Mutant::RequireHighjack do
   let(:object) { described_class.new(target, highjacked_calls.method(:push)) }
 
   let(:highjacked_calls) { [] }
diff --git a/spec/unit/mutant/runner_spec.rb b/spec/unit/mutant/runner_spec.rb
index 98190c12..b6de530e 100644
--- a/spec/unit/mutant/runner_spec.rb
+++ b/spec/unit/mutant/runner_spec.rb
@@ -1,5 +1,3 @@
-require 'spec_helper'
-
 class Double
   include Concord.new(:name, :attributes)
 
@@ -19,7 +17,7 @@ class Double
 end
 
 # FIXME: This is not even close to a mutation covering spec.
-describe Mutant::Runner do
+RSpec.describe Mutant::Runner do
   let(:object) { described_class.new(env) }
 
   let(:reporter) { Mutant::Reporter::Trace.new                        }
diff --git a/spec/unit/mutant/subject/context_spec.rb b/spec/unit/mutant/subject/context_spec.rb
index ecbed23a..93e2abda 100644
--- a/spec/unit/mutant/subject/context_spec.rb
+++ b/spec/unit/mutant/subject/context_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Subject, '#context' do
+RSpec.describe Mutant::Subject, '#context' do
   subject { object.context }
 
   let(:class_under_test) do
diff --git a/spec/unit/mutant/subject/method/instance_spec.rb b/spec/unit/mutant/subject/method/instance_spec.rb
index 5cc79833..528c4ee8 100644
--- a/spec/unit/mutant/subject/method/instance_spec.rb
+++ b/spec/unit/mutant/subject/method/instance_spec.rb
@@ -1,8 +1,4 @@
-# encoding: UTF-8
-
-require 'spec_helper'
-
-describe Mutant::Subject::Method::Instance do
+RSpec.describe Mutant::Subject::Method::Instance do
   let(:object)  { described_class.new(config, context, node) }
   let(:context) { double }
   let(:config)  { Mutant::Config::DEFAULT }
@@ -71,7 +67,7 @@ describe Mutant::Subject::Method::Instance do
   end
 end
 
-describe Mutant::Subject::Method::Instance::Memoized do
+RSpec.describe Mutant::Subject::Method::Instance::Memoized do
   let(:object)  { described_class.new(config, context, node) }
   let(:context) { double                                     }
   let(:config)  { Mutant::Config::DEFAULT                    }
diff --git a/spec/unit/mutant/subject/method/singleton_spec.rb b/spec/unit/mutant/subject/method/singleton_spec.rb
index 46e0c4f5..f36eaecf 100644
--- a/spec/unit/mutant/subject/method/singleton_spec.rb
+++ b/spec/unit/mutant/subject/method/singleton_spec.rb
@@ -1,8 +1,4 @@
-# encoding: UTF-8
-
-require 'spec_helper'
-
-describe Mutant::Subject::Method::Singleton do
+RSpec.describe Mutant::Subject::Method::Singleton do
 
   let(:object)  { described_class.new(config, context, node) }
   let(:config)  { Mutant::Config::DEFAULT                    }
diff --git a/spec/unit/mutant/subject_spec.rb b/spec/unit/mutant/subject_spec.rb
index a5aebcc4..c2b497d1 100644
--- a/spec/unit/mutant/subject_spec.rb
+++ b/spec/unit/mutant/subject_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Subject do
+RSpec.describe Mutant::Subject do
   let(:class_under_test) do
     Class.new(described_class) do
       def expression
diff --git a/spec/unit/mutant/test_spec.rb b/spec/unit/mutant/test_spec.rb
index 32452746..8e9b5e56 100644
--- a/spec/unit/mutant/test_spec.rb
+++ b/spec/unit/mutant/test_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::Test do
+RSpec.describe Mutant::Test do
   let(:object) { described_class.new(integration, expression) }
 
   let(:integration) { double('Integration', name: 'test-integration') }
diff --git a/spec/unit/mutant/warning_expectation.rb b/spec/unit/mutant/warning_expectation.rb
index 8ae734ed..e48bc9ef 100644
--- a/spec/unit/mutant/warning_expectation.rb
+++ b/spec/unit/mutant/warning_expectation.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::WarningExpectation do
+RSpec.describe Mutant::WarningExpectation do
   let(:object) { described_class.new(expected_warnings) }
 
   let(:expected_warnings) { [] }
diff --git a/spec/unit/mutant/warning_filter_spec.rb b/spec/unit/mutant/warning_filter_spec.rb
index 2f200c68..f917a9c9 100644
--- a/spec/unit/mutant/warning_filter_spec.rb
+++ b/spec/unit/mutant/warning_filter_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant::WarningFilter do
+RSpec.describe Mutant::WarningFilter do
   before do
     if RUBY_ENGINE.eql?('rbx')
       skip 'Disabled because expected warnings are from MRI'
diff --git a/spec/unit/mutant_spec.rb b/spec/unit/mutant_spec.rb
index 11cd5033..0abd0ca2 100644
--- a/spec/unit/mutant_spec.rb
+++ b/spec/unit/mutant_spec.rb
@@ -1,6 +1,4 @@
-require 'spec_helper'
-
-describe Mutant do
+RSpec.describe Mutant do
   let(:object) { described_class }
 
   describe '.zombify' do
diff --git a/test_app/spec/unit/test_app/literal/string_spec.rb b/test_app/spec/unit/test_app/literal/string_spec.rb
index b05a421a..1ea1947d 100644
--- a/test_app/spec/unit/test_app/literal/string_spec.rb
+++ b/test_app/spec/unit/test_app/literal/string_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe TestApp::Literal, '#string' do
+RSpec.describe TestApp::Literal, '#string' do
   subject { object.string }
 
   let(:object) { described_class.new }