Add extracted Repository::Diff#touches_path

lib/mutant/repository/diff.rb

@@ -22,12 +22,16 @@ class Error < RuntimeError; end
       # @raise [RepositoryError]
       #   when git command failed
       def touches?(path, line_range)
-        touched_paths
-          .from_right { |message| fail Error, message }
-          .fetch(path) { return false }
+        touched_path(path) { return false }
           .touches?(line_range)
       end
 
+      def touches_path?(path)
+        touched_path(path) { return false }
+
+        true
+      end
+
     private
 
       def repository_root
@@ -37,6 +41,10 @@ def repository_root
           .fmap(&world.pathname.public_method(:new))
       end
 
+      def touched_path(path, &block)
+        touched_paths.from_right { |message| fail Error, message }.fetch(path, &block)
+      end
+
       def touched_paths
         repository_root.bind(&method(:diff_index))
       end

spec/unit/mutant/repository/diff_spec.rb

@@ -1,54 +1,54 @@
 # frozen_string_literal: true
 
 describe Mutant::Repository::Diff do
-  describe '#touches?' do
-    def apply
-      subject.touches?(path, line_range)
-    end
-
-    subject { described_class.new(world: world, to: 'to_rev') }
+  subject { described_class.new(world: world, to: 'to_rev') }
+
+  let(:kernel)     { class_double(Kernel)        }
+  let(:line_range) { 4..5                        }
+  let(:path)       { Pathname.new('/foo/bar.rb') }
+  let(:pathname)   { class_double(Pathname)      }
+
+  let(:world) do
+    instance_double(
+      Mutant::World,
+      kernel:   kernel,
+      pathname: pathname
+    )
+  end
 
-    let(:kernel)     { class_double(Kernel)        }
-    let(:line_range) { 4..5                        }
-    let(:path)       { Pathname.new('/foo/bar.rb') }
-    let(:pathname)   { class_double(Pathname)      }
+  let(:raw_expectations) do
+    [
+      {
+        receiver:  world,
+        selector:  :capture_stdout,
+        arguments: [%w[git rev-parse --show-toplevel]],
+        reaction:  { return: Mutant::Either::Right.new("/foo\n") }
+      },
+      {
+        receiver:  world,
+        selector:  :capture_stdout,
+        arguments: [%w[git diff-index to_rev]],
+        reaction:  { return: Mutant::Either::Right.new(index_stdout) }
+      },
+      *file_diff_expectations
+    ]
+  end
 
-    let(:world) do
-      instance_double(
-        Mutant::World,
-        kernel:   kernel,
-        pathname: pathname
-      )
-    end
+  let(:file_diff_expectations) { [] }
 
-    let(:allowed_paths) do
-      %w[/foo bar.rb baz.rb].to_h do |path|
-        [path, Pathname.new(path)]
-      end
+  let(:allowed_paths) do
+    %w[/foo bar.rb baz.rb].to_h do |path|
+      [path, Pathname.new(path)]
     end
+  end
 
-    let(:file_diff_expectations) { [] }
-
-    let(:raw_expectations) do
-      [
-        {
-          receiver:  world,
-          selector:  :capture_stdout,
-          arguments: [%w[git rev-parse --show-toplevel]],
-          reaction:  { return: Mutant::Either::Right.new("/foo\n") }
-        },
-        {
-          receiver:  world,
-          selector:  :capture_stdout,
-          arguments: [%w[git diff-index to_rev]],
-          reaction:  { return: Mutant::Either::Right.new(index_stdout) }
-        },
-        *file_diff_expectations
-      ]
-    end
+  before do
+    allow(pathname).to receive(:new, &allowed_paths.public_method(:fetch))
+  end
 
-    before do
-      allow(pathname).to receive(:new, &allowed_paths.public_method(:fetch))
+  describe '#touches?' do
+    def apply
+      subject.touches?(path, line_range)
     end
 
     context 'when file is not touched in the diff' do
@@ -123,4 +123,31 @@ def apply
       end
     end
   end
+
+  describe '#touches_path?' do
+    def apply
+      subject.touches_path?(path)
+    end
+
+    context 'when file is not touched in the diff' do
+      let(:index_stdout) { '' }
+
+      it 'returns false' do
+        verify_events { expect(apply).to be(false) }
+      end
+    end
+
+    context 'when file is touched in the diff' do
+      let(:index_stdout) do
+        <<~STR
+          :000000 000000 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000 M\tbar.rb
+          :000000 000000 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000 M\tbaz.rb
+        STR
+      end
+
+      it 'returns true' do
+        verify_events { expect(apply).to be(true) }
+      end
+    end
+  end
 end