old_contents: from nose.tools import istest, assert_equal
  
  from spur import LocalShell
  
  shell = LocalShell()
  
  @istest
  def output_of_run_is_stored():
      result = shell.run(["echo", "hello"])
      assert_equal("hello\n", result.output)
  
  @istest
  def cwd_of_run_can_be_set():
      result = shell.run(["pwd"], cwd="/")
      assert_equal("/\n", result.output)
  
new_contents: from nose.tools import istest, assert_equal
  
  from spur import LocalShell
  
  shell = LocalShell()
  
  @istest
  def output_of_run_is_stored():
      result = shell.run(["echo", "hello"])
      assert_equal("hello\n", result.output)
  
  @istest
  def cwd_of_run_can_be_set():
      result = shell.run(["pwd"], cwd="/")
      assert_equal("/\n", result.output)
  
  @istest
  def environment_variables_can_be_added_for_run():
      result = shell.run(["sh", "-c", "echo $NAME"], update_env={"NAME": "Bob"})
      assert_equal("Bob\n", result.output)
  
subject: Add test for LocalShell.run with update_env