diff --git a/lib/pry.rb b/lib/pry.rb
index d949cf3e..b8707c53 100644
--- a/lib/pry.rb
+++ b/lib/pry.rb
@@ -22,34 +22,48 @@ class Pry
     end
   end
 
+  def self.reset_defaults
+    self.input = Input.new
+    self.output = Output.new
+
+    self.default_prompt = proc do |v, nest|
+      if nest == 0
+        "pry(#{Pry.view(v)})> "
+      else
+        "pry(#{Pry.view(v)}):#{Pry.view(nest)}> "
+      end
+    end
+    
+    self.wait_prompt = proc do |v, nest|
+      if nest == 0
+        "pry(#{Pry.view(v)})* "
+      else
+        "pry(#{Pry.view(v)}):#{Pry.view(nest)}* "
+      end
+    end
+  end
+
   # class accessors
   class << self
     attr_reader :nesting
     attr_accessor :last_result
     attr_accessor :default_prompt, :wait_prompt
+    attr_accessor :input, :output
   end
 
-  self.default_prompt = proc do |v, nest|
-    if nest == 0
-      "pry(#{Pry.view(v)})> "
-    else
-      "pry(#{Pry.view(v)}):#{Pry.view(nest)}> "
-    end
-  end
-  
-  self.wait_prompt = proc do |v, nest|
-    if nest == 0
-      "pry(#{Pry.view(v)})* "
-    else
-      "pry(#{Pry.view(v)}):#{Pry.view(nest)}* "
-    end
+  self.reset_defaults
+
+  @nesting = []
+
+  def @nesting.level
+    last.is_a?(Array) ? last.first : nil
   end
 
   attr_accessor :input, :output
   attr_accessor :default_prompt, :wait_prompt
   attr_reader :last_result
   
-  def initialize(input = Input.new, output = Output.new)
+  def initialize(input = Pry.input, output = Pry.output)
     @input = input
     @output = output
 
@@ -57,11 +71,6 @@ class Pry
     @wait_prompt = Pry.wait_prompt
   end
 
-  @nesting = []
-
-  def @nesting.level
-    last.is_a?(Array) ? last.first : nil
-  end
 
   def nesting
     self.class.nesting
@@ -123,7 +132,7 @@ class Pry
     eval_string = ""
     loop do
       val = input.read(prompt(eval_string, target, nesting.level))
-      eval_string += "#{val.chomp}\n"
+      eval_string << "#{val.chomp}\n"
       process_commands(val, eval_string, target)
       
       break eval_string if valid_expression?(eval_string)
@@ -163,6 +172,7 @@ class Pry
       eval_string.clear
     when /^cd\s+(.+)/
       obj = $~.captures.first
+      output.cd(obj)
       target.eval("#{obj}.pry")
       eval_string.clear
     when /^show_doc\s*(.+)/
diff --git a/lib/pry/output.rb b/lib/pry/output.rb
index d083e443..b117f782 100644
--- a/lib/pry/output.rb
+++ b/lib/pry/output.rb
@@ -94,6 +94,7 @@ class Pry
     end
 
     def exit() end
+    def cd(*) end
     def jump_to(nesting_level_breakout) end
     def exit_program() end
   end
diff --git a/test/test.rb b/test/test.rb
new file mode 100644
index 00000000..1e1a70b7
--- /dev/null
+++ b/test/test.rb
@@ -0,0 +1,103 @@
+direc = File.dirname(__FILE__)
+
+require 'bacon'
+require "#{direc}/../lib/pry"
+require "#{direc}/test_helper"
+
+describe Pry do
+  describe "open a Pry session on an object" do
+    describe "rep" do
+      it 'should set an ivar on an object' do
+        input_string = "@x = 10"
+        input = InputTester.new(input_string)
+        output = OutputTester.new
+        o = Object.new
+
+        pry_tester = Pry.new(input, output)
+        pry_tester.rep(o)
+        o.instance_variable_get(:@x).should == 10
+      end
+
+      it 'should make self evaluate to the receiver of the rep session' do
+        output = OutputTester.new
+        o = Object.new
+        
+        pry_tester = Pry.new(InputTester.new("self"), output)
+        pry_tester.rep(o)
+        output.output_buffer.should == o
+      end
+    end
+
+    describe "repl" do
+      describe "commands" do
+
+        before do
+          Pry.input = InputTester.new("exit")
+          Pry.output = OutputTester.new
+        end
+
+        after do
+          Pry.reset_defaults
+        end
+        
+        { "!" => "refresh",
+          "help" => "show_help",
+          "nesting" => "show_nesting",
+          "status" => "show_status",
+          "cat dummy" => "cat",
+          "cd 3" => "cd",
+          "ls" => "ls",
+          "show_method test_method" => "show_method",
+          "show_imethod test_method" => "show_method",
+          "show_doc test_method" => "show_doc",
+          "show_idoc test_method" => "show_doc",
+          "jump_to 0" => "jump_to"
+        }.each do |command, meth|
+
+          eval %{
+            it "should invoke output##{meth}  when #{command} command entered" do
+              input_strings = ["#{command}", "exit"]
+              input = InputTester.new(input_strings)
+              output = OutputTester.new
+              o = Class.new
+          
+              pry_tester = Pry.new(input, output)
+              pry_tester.repl(o)
+
+              output.#{meth}_invoked.should == true
+              output.session_end_invoked.should == true
+            end
+          }
+
+
+          # it "should invoke output#help when help command entered" do
+          #   input_strings = ["help", "exit"]
+          #   input = InputTester.new(input_strings)
+          #   output = OutputTester.new
+          #   o = Object.new
+          
+          #   pry_tester = Pry.new(input, output)
+          #   pry_tester.repl(o)
+
+          #   output.show_help_invoked.should == true
+          #   output.session_end_invoked.should == true
+          # end
+
+          # it 'should set an ivar on an object and exit the repl' do
+          #   input_strings = ["@x = 10", "exit"]
+          #   input = InputTester.new(input_strings)
+          #   output = OutputTester.new
+
+          #   o = Object.new
+
+          #   pry_tester = Pry.new(input, output)
+          #   pry_tester.repl(o)
+
+          #   o.instance_variable_get(:@x).should == 10
+          #   output.session_end_invoked.should == true
+          # end
+        end
+      end
+    end
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
new file mode 100644
index 00000000..ec8c96a4
--- /dev/null
+++ b/test/test_helper.rb
@@ -0,0 +1,38 @@
+class Object
+  def test_method
+  end
+end
+
+class InputTester
+  def initialize(actions)
+    @orig_actions = Array(actions.dup)
+    @actions = Array(actions)
+  end
+
+  def read(*)
+    @actions.shift
+  end
+
+  def rewind
+    @actions = @orig_actions
+  end
+end
+
+class OutputTester
+  attr_reader :output_buffer
+
+  def initialize
+    @output_buffer = ""
+  end
+
+  def print(val)
+    @output_buffer = val
+    puts val.inspect
+  end
+
+  def method_missing(meth_name, *args, &block)
+    define_singleton_method("#{meth_name}_invoked") { true }
+  end
+end
+    
+