Use rubygems require extension

lib/mutest.rb

@@ -179,6 +179,7 @@ def self.ci?
 require 'mutest/expression/namespace'
 require 'mutest/test'
 require 'mutest/integration'
+require 'mutest/integration/null'
 require 'mutest/selector'
 require 'mutest/selector/expression'
 require 'mutest/config'
@@ -206,6 +207,7 @@ def self.ci?
 require 'mutest/reporter/cli/tput'
 require 'mutest/reporter/cli/format'
 require 'mutest/repository'
+require 'mutest/requirer'
 require 'mutest/zombifier'
 
 module Mutest
@@ -230,6 +232,7 @@ class Config
         process: Process
       ),
       jobs:              ::Parallel.processor_count,
+      requirer:          Requirer.new,
       kernel:            Kernel,
       load_path:         $LOAD_PATH,
       matcher:           Matcher::Config::DEFAULT,

lib/mutest/cli.rb

@@ -99,7 +99,7 @@ def add_environment_options(opts)
     #
     # @return [undefined]
     def setup_integration(name)
-      with(integration: Integration.setup(config.kernel, name))
+      with(integration: Integration.setup(config.requirer, name))
     rescue LoadError
       raise Error, "Could not load integration #{name.inspect} (you may want to try installing the gem mutest-#{name})"
     end

lib/mutest/config.rb

@@ -16,6 +16,7 @@ class Config
       :matcher,
       :open3,
       :pathname,
+      :requirer,
       :requires,
       :reporter,
       :zombie

lib/mutest/integration.rb

@@ -47,29 +47,5 @@ def setup
     def expression_parser
       config.expression_parser
     end
-
-    # Null integration that never kills a mutation
-    class Null < self
-      # Available tests for integration
-      #
-      # @return [Enumerable<Test>]
-      def all_tests
-        EMPTY_ARRAY
-      end
-
-      # Run a collection of tests
-      #
-      # @param [Enumerable<Mutest::Test>] tests
-      #
-      # @return [Result::Test]
-      def call(tests)
-        Result::Test.new(
-          output:  '',
-          passed:  true,
-          runtime: 0.0,
-          tests:   tests
-        )
-      end
-    end # Null
   end # Integration
 end # Mutest

lib/mutest/integration/null.rb

@@ -0,0 +1,27 @@
+module Mutest
+  class Integration
+    # Null integration that never kills a mutation
+    class Null < self
+      # Available tests for integration
+      #
+      # @return [Enumerable<Test>]
+      def all_tests
+        EMPTY_ARRAY
+      end
+
+      # Run a collection of tests
+      #
+      # @param [Enumerable<Mutest::Test>] tests
+      #
+      # @return [Result::Test]
+      def call(tests)
+        Result::Test.new(
+          output:  '',
+          passed:  true,
+          runtime: 0.0,
+          tests:   tests
+        )
+      end
+    end # Null
+  end # Integration
+end # Mutest

lib/mutest/requirer.rb

@@ -0,0 +1,6 @@
+module Mutest
+  # Class that exposes #require as a public method
+  class Requirer
+    public :require
+  end # Requirer
+end # Mutest

spec/unit/mutest/cli_spec.rb

@@ -137,18 +137,30 @@
     end
 
     context 'with use flag' do
-      context 'when integration exists' do
+      context 'when using the existing integration with rspec' do
         let(:flags) { %w[--use rspec] }
+        let(:expected_integration) { Mutest::Integration::Rspec }
 
         before do
-          expect(Kernel).to receive(:require)
+          expect(Mutest::Config::DEFAULT.requirer).to receive(:require)
             .with('mutest/integration/rspec')
             .and_call_original
         end
 
         it_should_behave_like 'a cli parser'
+      end
 
-        let(:expected_integration) { Mutest::Integration::Rspec }
+      context 'when specifying the default null integration explicitely' do
+        let(:flags) { %w[--use null] }
+        let(:expected_integration) { Mutest::Integration::Null }
+
+        before do
+          expect(Mutest::Config::DEFAULT.requirer).to receive(:require)
+            .with('mutest/integration/null')
+            .and_call_original
+        end
+
+        it_should_behave_like 'a cli parser'
       end
 
       context 'when integration does NOT exist' do

spec/unit/mutest/integration_spec.rb

@@ -11,13 +11,13 @@
   end
 
   describe '.setup' do
-    subject { described_class.setup(kernel, name) }
+    subject { described_class.setup(requirer, name) }
 
-    let(:name)   { 'null'               }
-    let(:kernel) { class_double(Kernel) }
+    let(:name)     { 'null'               }
+    let(:requirer) { Mutest::Requirer.new }
 
     before do
-      expect(kernel).to receive(:require)
+      expect(requirer).to receive(:require)
         .with('mutest/integration/null')
     end