Add ObjectSpace to Mutant::World

Author: mbj

lib/mutant.rb

@@ -161,6 +161,7 @@ def self.ci?
 require 'mutant/integration'
 require 'mutant/selector'
 require 'mutant/selector/expression'
+require 'mutant/selector/null'
 require 'mutant/config'
 require 'mutant/cli'
 require 'mutant/color'

lib/mutant/selector/null.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Mutant
+  class Selector
+    # Selector that never returns tests
+    class Null < self
+      # Tests for subject
+      #
+      # @param [Subject] subject
+      #
+      # @return [Enumerable<Test>]
+      def call(_subject)
+        EMPTY_ARRAY
+      end
+    end # Null
+  end # Selector
+end # Mutant

spec/unit/mutant/selector/null_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+RSpec.describe Mutant::Selector::Null do
+  describe '#call' do
+    subject { described_class.new }
+
+    let(:mutant_subject) { instance_double(Mutant::Subject) }
+
+    def apply
+      subject.call(mutant_subject)
+    end
+
+    it 'returns no tests' do
+      expect(apply).to eql([])
+    end
+  end
+end