Bitmask file creation modes allow for Tempfile compatability.

lib/fakefs/file.rb

@@ -13,6 +13,19 @@ module FakeFS
 
     FILE_CREATION_MODES = MODES - [READ_ONLY, READ_WRITE]
 
+    MODE_BITMASK = RealFile::RDONLY   |
+                   RealFile::WRONLY   |
+                   RealFile::RDWR     |
+                   RealFile::APPEND   |
+                   RealFile::CREAT    |
+                   RealFile::EXCL     |
+                   RealFile::NONBLOCK |
+                   RealFile::TRUNC    |
+                   RealFile::NOCTTY   |
+                   RealFile::SYNC
+
+    FILE_CREATION_BITMASK = RealFile::CREAT
+
     def self.extname(path)
       RealFile.extname(path)
     end
@@ -28,8 +41,9 @@ module FakeFS
     class << self
       alias_method :exists?, :exist?
 
-      # Assuming that everyone can read files
+      # Assuming that everyone can read and write files
       alias_method :readable?, :exist?
+      alias_method :writable?, :exist?
     end
 
     def self.mtime(path)
@@ -248,11 +262,15 @@ module FakeFS
     end
 
     def file_creation_mode?
-      mode_in? FILE_CREATION_MODES
+      mode_in?(FILE_CREATION_MODES) || mode_in_bitmask?(FILE_CREATION_BITMASK)
     end
 
     def mode_in?(list)
-      list.any? { |element| @mode.include?(element) }
+      list.any? { |element| @mode.include?(element) } if @mode.respond_to?(:include?)
+    end
+
+    def mode_in_bitmask?(mask)
+      (@mode & mask) != 0 if @mode.is_a?(Integer)
     end
 
     def create_missing_file

test/fakefs_test.rb

@@ -109,6 +109,18 @@ class FakeFSTest < Test::Unit::TestCase
 
     assert File.exists?(path)
     assert File.readable?(path)
+    assert File.writable?(path)
+  end
+
+  def test_can_create_files_with_bitmasks
+    path = '/path/to/file.txt'
+    File.open(path, File::RDWR | File::CREAT) do |f|
+      f.write "Yatta!"
+    end
+
+    assert File.exists?(path)
+    assert File.readable?(path)
+    assert File.writable?(path)
   end
 
   def test_file_opens_in_read_only_mode
@@ -121,6 +133,16 @@ class FakeFSTest < Test::Unit::TestCase
     end
   end
 
+  def test_file_opens_in_read_only_mode_with_bitmasks
+    File.open("foo", "w") { |f| f << "foo" }
+
+    f = File.open("foo", File::RDONLY)
+
+    assert_raises(IOError) do
+      f << "bar"
+    end
+  end
+
   def test_file_opens_in_invalid_mode
     FileUtils.touch("foo")
 
@@ -146,6 +168,17 @@ class FakeFSTest < Test::Unit::TestCase
     assert File.exists?("foo")
   end
 
+  def test_creates_files_in_write_only_mode_with_bitmasks
+    File.open("foo", File::WRONLY | File::CREAT)
+    assert File.exists?("foo")
+  end
+
+  def test_raises_in_write_only_mode_without_create_bitmask
+    assert_raises(Errno::ENOENT) do
+      File.open("foo", File::WRONLY)
+    end
+  end
+
   def test_creates_files_in_read_write_truncate_mode
     File.open("foo", "w+")
     assert File.exists?("foo")