Starting to write the new initializer

railties/test/new_initializer_test.rb

+require 'abstract_unit'
+require 'active_support/ruby/shim'
+
+module Rails
+  class Initializer
+    class Error < StandardError ; end
+    class Runner
+      def initialize
+        @names = {}
+        @initializers = []
+      end
+      
+      def add(name, options = {}, &block)
+        if other = options[:before] || options[:after] and !@names[other]
+          raise Error, "The #{other.inspect} initializer does not exist"
+        end
+        
+        Class.new(Initializer, &block).new.tap do |initializer|
+          index = if options[:before]
+            @initializers.index(@names[other])
+          elsif options[:after]
+            @initializers.index(@names[other]) + 1
+          else
+            -1
+          end
+          
+          @initializers.insert(index, initializer)
+          @names[name] = initializer
+        end
+      end
+      
+      def run
+        @initializers.each { |init| init.run }
+      end
+    end
+    
+    def self.run(&blk)
+      define_method(:run, &blk)
+    end
+  end
+end
+
+
+class InitializerRunnerTest < ActiveSupport::TestCase
+  
+  def setup
+    @runner = Rails::Initializer::Runner.new
+  end
+  
+  test "A new runner can be created" do
+    assert @runner
+  end
+  
+  test "You can create initializers" do
+    init = @runner.add :foo do
+      
+    end
+    
+    assert_kind_of Rails::Initializer, init
+  end
+  
+  test "The initializers actually get run when the runner is run" do
+    state = nil
+    
+    @runner.add :foo do
+      run { state = true }
+    end
+    
+    @runner.run
+    assert state
+  end
+  
+  test "By default, initializers get run in the order that they are added" do
+    state = []
+    
+    @runner.add :first do
+      run { state << :first }
+    end
+    
+    @runner.add :second do
+      run { state << :second }
+    end
+    
+    @runner.run
+    assert_equal [:first, :second], state
+  end
+  
+  test "Raises an exception if :before or :after are specified, but don't exist" do
+    assert_raise(Rails::Initializer::Error) do
+      @runner.add(:fail, :before => :whale) { 1 }
+    end
+    
+    assert_raise(Rails::Initializer::Error) do
+      @runner.add(:fail, :after => :whale) { 1 }
+    end
+  end
+  
+  test "When adding an initializer, specifying :after allows you to move an initializer after another" do
+    state = []
+    
+    @runner.add :first do
+      run { state << :first }
+    end
+    
+    @runner.add :second do
+      run { state << :second }
+    end
+    
+    @runner.add :third, :after => :first do
+      run { state << :third }
+    end
+    
+    @runner.run
+    assert_equal [:first, :third, :second], state
+  end
+  
+end
+