Extract file list calculation into seperate, testable class.

lib/rspec/parts.rb

@@ -1,5 +1,6 @@
 require "rspec/parts/version"
 require "rspec/parts/configuration"
+require "rspec/parts/file_list"
 
 module Rspec
   module Parts

lib/rspec/parts/file_list.rb

@@ -0,0 +1,51 @@
+require 'rake/file_list'
+
+# Grabbed from ActiveSupport
+# activesupport/lib/active_support/core_ext/array/grouping.rb, line 60
+class Array
+  def in_groups(number, fill_with = nil)
+    # size.div number gives minor group size;
+    # size % number gives how many objects need extra accommodation;
+    # each group hold either division or division + 1 items.
+    division = size.div number
+    modulo = size % number
+
+    # create a new array avoiding dup
+    groups = []
+    start = 0
+
+    number.times do |index|
+      length = division + (modulo > 0 && modulo > index ? 1 : 0)
+      groups << last_group = slice(start, length)
+      last_group << fill_with if fill_with != false &&
+        modulo > 0 && length == division
+      start += length
+    end
+
+    if block_given?
+      groups.each { |g| yield(g) }
+    else
+      groups
+    end
+  end
+end
+
+module Rspec
+  module Parts
+    class FileList
+      def self.from(glob: glob, groups: groups, part: part)
+        total_file_list = Rake::FileList.new
+
+        Dir.glob(glob).each do |spec_directory|
+          directory_file_list = Rake::FileList.new
+          directory_file_list.add("#{spec_directory}/**/*_spec.rb")
+          subset_of_directory_file_list = directory_file_list.to_a.in_groups(groups, false).at(part)
+          total_file_list.add(subset_of_directory_file_list)
+        end
+
+        total_file_list
+      end
+    end
+  end
+end
+

lib/tasks/rspec_parts.rake

@@ -1,19 +1,13 @@
+require 'rspec/parts'
+
 if defined?(RSpec)
   namespace :spec do
     desc 'Run part M of N specs'
     RSpec::Core::RakeTask.new(:part, :part, :groups) do |task, task_args|
       groups = task_args[:groups].to_i == 0 ? 4 : task_args[:groups].to_i
       part = (task_args[:part].to_i == 0 ? 1 : task_args[:part].to_i) - 1
 
-      total_file_list = FileList.new
-
-      Dir.glob('spec/*').each do |spec_directory|
-        directory_file_list = FileList.new
-        directory_file_list.add("#{spec_directory}/**/*_spec.rb")
-        subset_of_directory_file_list = directory_file_list.to_a.in_groups(groups, false).at(part)
-        total_file_list.add(subset_of_directory_file_list)
-      end
-
+      total_file_list = Rspec::Parts::FileList.from(glob: 'spec/*', groups: groups, part: part)
       total_file_list.exclude('spec/controllers/jasmine_fixture_generation/*.rb')
 
       task.rspec_opts = '--profile --tag ~nginx --format progress'

rspec-parts.gemspec

@@ -28,6 +28,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_development_dependency "bundler", "~> 1.10"
-  spec.add_development_dependency "rake", "~> 10.0"
+  spec.add_development_dependency "pry-nav"
   spec.add_development_dependency "rspec"
+  spec.add_dependency "rake"
 end

spec/rspec/parts/file_list_spec.rb

@@ -0,0 +1,36 @@
+require 'spec_helper'
+
+describe Rspec::Parts::FileList do
+  describe '.from' do
+    let(:subject) { described_class.from(glob: directory_glob, groups: 2, part: part) }
+
+    context 'given a directory with two files in two directories' do
+      let(:directory_glob) { 'spec/*' }
+
+      context 'part one' do
+        let(:part) { 0 }
+        it 'splits the controllers and models directory appropriately' do
+          filelist = subject.to_a
+          aggregate_failures do
+            expect(filelist).to include('spec/controllers/a_spec.rb')
+            expect(filelist).to include('spec/models/a_spec.rb')
+            expect(filelist).to include('spec/rspec/parts/file_list_spec.rb')
+            expect(filelist).to include('spec/rspec/parts/configuration_spec.rb')
+          end
+        end
+      end
+
+      context 'part two' do
+        let(:part) { 1 }
+        it 'splits the controllers and models directory appropriately' do
+          filelist = subject.to_a
+          aggregate_failures do
+            expect(filelist).to include('spec/controllers/b_spec.rb')
+            expect(filelist).to include('spec/models/b_spec.rb')
+            expect(filelist).to include('spec/rspec/parts_spec.rb')
+          end
+        end
+      end
+    end
+  end
+end