class ActiveSupport::Testing::SimpleStubs

:nodoc:
Manages stubs for TimeHelpers

def initialize 

def initialize
  @stubs = Concurrent::Map.new { |h, k| h[k] = {} }
end

def stub_object(object, method_name, &block)

Time.current # => Wed, 24 Nov 2004 01:04:44 EST -05:00
simple_stubs.stub_object(Time, :now) { at(target.to_i) }
target = Time.zone.local(2004, 11, 24, 1, 4, 44)
Time.current # => Sat, 09 Nov 2013 15:34:49 EST -05:00
so that removing this stub will restore the original implementation.
If the method is already stubbed, remove that stub
Stubs object.method_name with the given block 
def stub_object(object, method_name, &block)
  if stub = stubbing(object, method_name)
    unstub_object(stub)
  end
  new_name = "__simple_stub__#{method_name}"
  @stubs[object.object_id][method_name] = Stub.new(object, method_name, new_name)
  object.singleton_class.alias_method new_name, method_name
  object.define_singleton_method(method_name, &block)
end

def stubbed?

Returns true if any stubs are set, false if there are none 
def stubbed?
  !@stubs.empty?
end

def stubbing(object, method_name)

(nil if it is not stubbed)
Returns the Stub for object#method_name 
def stubbing(object, method_name)
  @stubs[object.object_id][method_name]
end

def unstub_all!

Remove all object-method stubs held by this instance 
def unstub_all!
  @stubs.each_value do |object_stubs|
    object_stubs.each_value do |stub|
      unstub_object(stub)
    end
  end
  @stubs.clear
end

def unstub_object(stub)

Restores the original object.method described by the Stub 
def unstub_object(stub)
  singleton_class = stub.object.singleton_class
  singleton_class.silence_redefinition_of_method stub.method_name
  singleton_class.alias_method stub.method_name, stub.original_method
  singleton_class.undef_method stub.original_method
end