Aliasing File.readable? to File.exist? so Rack::File can work

lib/fakefs/file.rb

@@ -41,6 +41,9 @@ module FakeFS
 
     class << self
       alias_method :exists?, :exist?
+
+      # Assuming that everyone can read files
+      alias_method :readable?, :exist?
     end
 
     def self.size(path)

test/fakefs_test.rb

@@ -94,6 +94,7 @@ class FakeFSTest < Test::Unit::TestCase
     end
 
     assert File.exists?(path)
+    assert File.readable?(path)
   end
 
   def test_file_opens_in_read_only_mode