Split differ interface and mutation cover Mutant::Differ.build

lib/mutant/differ.rb

@@ -45,8 +45,8 @@ module Mutant
     #
     # @api private
     #
-    def self.new(old, new)
-      super(lines(old), lines(new))
+    def self.build(old, new)
+      new(lines(old), lines(new))
     end
 
   private

lib/mutant/reporter/cli/printer/mutation.rb

@@ -38,7 +38,7 @@ module Mutant
           #
           def colorized_diff
             original, current = mutation.original_source, mutation.source
-            differ = Differ.new(original, current)
+            differ = Differ.build(original, current)
             diff = color? ? differ.colorized_diff : differ.diff
 
             if diff.empty?

spec/unit/mutant/differ/class_methods/build_spec.rb

@@ -0,0 +1,12 @@
+require 'spec_helper'
+
+describe Mutant::Differ, '.build' do
+  let(:object) { described_class }
+
+  subject { object.build(old_string, new_string) }
+
+  let(:old_string) { "foo\nbar" }
+  let(:new_string) { "bar\nbaz" }
+
+  it { should eql(Mutant::Differ.new(%w(foo bar), %w(bar baz))) }
+end

spec/unit/mutant/differ/diff_spec.rb

@@ -5,18 +5,18 @@ describe Mutant::Differ, '#diff' do
 
   subject { object.diff }
 
-  context 'when there is a diff that is at beginning of hunk' do
-    let(:old) { "foo\nbar" }
-    let(:new) { "baz\nbar" }
+  context 'when there is a diff at beginning of hunk' do
+    let(:old) { %w(foo bar) }
+    let(:new) { %w(baz bar) }
 
     it { should eql("@@ -1,3 +1,3 @@\n-foo\n+baz\n bar\n") }
 
     it_should_behave_like 'an idempotent method'
   end
 
-  context 'when there is a diff that is NOT at beginning of hunk' do
-    let(:old) { "foo\nbar" }
-    let(:new) { "foo\nbaz\nbar" }
+  context 'when there is a diff NOT at beginning of hunk' do
+    let(:old) { %w(foo bar) }
+    let(:new) { %w(foo baz bar) }
 
     it { should eql("@@ -1,3 +1,4 @@\n foo\n+baz\n bar\n") }