add FileUtils.cp & tests

lib/fakefs.rb

@@ -25,6 +25,25 @@ module FakeFS
       FileSystem.add(path, MockSymlink.new(target))
     end
 
+    def cp(src, dest)
+      dst_file = FileSystem.find(dest)
+      src_file = FileSystem.find(src)
+
+      if dst_file
+        raise Errno::EEXIST, dest
+      end
+
+      if !src_file
+        raise Errno::ENOENT, src
+      end
+
+      if File.directory? src_file
+        raise Errno::EISDIR, src
+      end
+
+      FileSystem.add(dest, src_file.entry.clone)
+    end
+
     def cp_r(src, dest)
       # This error sucks, but it conforms to the original Ruby
       # method.
@@ -89,15 +108,27 @@ module FakeFS
     end
 
     def self.directory?(path)
-      FileSystem.find(path).entry.is_a? MockDir
+      if path.respond_to? :entry
+        path.entry.is_a? MockDir
+      else
+        FileSystem.find(path).entry.is_a? MockDir
+      end
     end
 
     def self.symlink?(path)
-      FileSystem.find(path).is_a? MockSymlink
+      if path.respond_to? :entry
+        path.is_a? MockSymlink
+      else
+        FileSystem.find(path).is_a? MockSymlink
+      end
     end
 
     def self.file?(path)
-      FileSystem.find(path).entry.is_a? MockFile
+      if path.respond_to? :entry
+        path.entry.is_a? MockFile
+      else
+        FileSystem.find(path).entry.is_a? MockFile
+      end
     end
 
     def self.expand_path(*args)

test/fakefs_test.rb

@@ -298,6 +298,35 @@ class FakeFSTest < Test::Unit::TestCase
     assert_equal 'bar', File.open('baz'){|f| f.read }
   end
 
+  def test_cp_actually_works
+    File.open('foo', 'w') {|f| f.write 'bar' }
+    FileUtils.cp('foo', 'baz')
+    assert_equal 'bar', File.read('baz')
+  end
+
+  def test_cp_fails_on_dest_exists
+    File.open('foo', 'w') {|f| f.write 'bar' }
+    FileUtils.mkdir_p 'baz'
+
+    assert_raise Errno::EEXIST do
+      FileUtils.cp('foo', 'baz')
+    end
+  end
+
+  def test_cp_fails_on_no_source
+    assert_raise Errno::ENOENT do
+      FileUtils.cp('foo', 'baz')
+    end
+  end
+
+  def test_cp_fails_on_directory_copy
+    FileUtils.mkdir_p 'baz'
+
+    assert_raise Errno::EISDIR do
+      FileUtils.cp('baz', 'bar')
+    end
+  end
+
   def test_cp_r_doesnt_tangle_files_together
     File.open('foo', 'w') {|f| f.write 'bar' }
     FileUtils.cp_r('foo', 'baz')