Fix integration coverage

config/flay.yml

@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 1181
+total_score: 1177

lib/mutant/cli.rb

@@ -103,7 +103,7 @@ module Mutant
     #
     # @return [undefined]
     def setup_integration(name)
-      with(integration: Integration.setup(name))
+      with(integration: Integration.setup(config.kernel, name))
     rescue LoadError
       raise Error, "Could not load integration #{name.inspect} (you may want to try installing the gem mutant-#{name})"
     end

lib/mutant/integration.rb

@@ -4,38 +4,23 @@ module Mutant
   class Integration
     include AbstractType, Adamantium::Flat, Concord.new(:config)
 
-    REGISTRY = {}
-
     # Setup integration
     #
-    # @param [String] name
+    # Integrations are supposed to define a constant under
+    # Mutant::Integration named after the capitalized +name+
+    # parameter.
     #
-    # @return [Integration]
-    def self.setup(name)
-      require "mutant/integration/#{name}"
-      lookup(name)
+    # This avoids having to maintain a mutable registry.
+    #
+    # @param kernel [Kernel]
+    # @param name [String]
+    #
+    # @return [Class<Integration>]
+    def self.setup(kernel, name)
+      kernel.require("mutant/integration/#{name}")
+      const_get(name.capitalize)
     end
 
-    # Lookup integration for name
-    #
-    # @param [String] name
-    #
-    # @return [Integration]
-    #   if found
-    def self.lookup(name)
-      REGISTRY.fetch(name)
-    end
-
-    # Register integration
-    #
-    # @param [String] name
-    #
-    # @return [undefined]
-    def self.register(name)
-      REGISTRY[name] = self
-    end
-    private_class_method :register
-
     # Perform integration setup
     #
     # @return [self]
@@ -67,8 +52,6 @@ module Mutant
     # Null integration that never kills a mutation
     class Null < self
 
-      register('null')
-
       # Available tests for integration
       #
       # @return [Enumerable<Test>]
@@ -91,6 +74,5 @@ module Mutant
       end
 
     end # Null
-
   end # Integration
 end # Mutant

lib/mutant/integration/rspec.rb

@@ -28,8 +28,6 @@ module Mutant
 
       private_constant(*constants(false))
 
-      register 'rspec'
-
       # Initialize rspec integration
       #
       # @return [undefined]

spec/unit/mutant/cli_spec.rb

@@ -151,6 +151,12 @@ Options:
       context 'when integration exists' do
         let(:flags) { %w[--use rspec] }
 
+        before do
+          expect(Kernel).to receive(:require)
+            .with('mutant/integration/rspec')
+            .and_call_original
+        end
+
         it_should_behave_like 'a cli parser'
 
         let(:expected_integration) { Mutant::Integration::Rspec }

spec/unit/mutant/integration_spec.rb

@@ -10,6 +10,20 @@ RSpec.describe Mutant::Integration do
     subject { object.setup }
     it_should_behave_like 'a command method'
   end
+
+  describe '.setup' do
+    subject { described_class.setup(kernel, name) }
+
+    let(:name)   { 'null'               }
+    let(:kernel) { class_double(Kernel) }
+
+    before do
+      expect(kernel).to receive(:require)
+        .with('mutant/integration/null')
+    end
+
+    it { should be(Mutant::Integration::Null) }
+  end
 end
 
 RSpec.describe Mutant::Integration::Null do