diff --git a/README.md b/README.md
index f40f03866..d7953036d 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,24 @@
 mruby-dir
 =========
 
+Dir class for mruby.  Supported methods are:
+
+`.chdir`
+`.delete`
+`.entries`
+`.exist?`
+`.foreach`
+`.getwd`
+`.mkdir`
+`.open`
+`#close`
+`#each`
+`#read`
+`#rewind`
+`#seek`
+`#tell`
+
+
 ## License
 
 Copyright (c) 2012 Internet Initiative Japan Inc.
diff --git a/test/dir.rb b/test/dir.rb
index e69de29bb..95acf7725 100644
--- a/test/dir.rb
+++ b/test/dir.rb
@@ -0,0 +1,110 @@
+# Note: testing telldir(3) and seekdir(3) in portable manner is very hard.
+
+assert('Dir') do
+  assert_equal(Class, Addrinfo.class)
+end
+
+assert('DirTest.setup') do
+  DirTest.setup
+end
+
+assert('Dir.chdir') do
+  assert_equal 0, Dir.chdir(DirTest.sandbox)
+end
+
+assert('Dir.entries') do
+  a = Dir.entries(DirTest.sandbox)
+  assert_true a.include? "a"
+  assert_true a.include? "b"
+end
+
+assert('Dir.exist?') do
+  assert_true Dir.exist?(DirTest.sandbox)
+  assert_false Dir.exist?(DirTest.sandbox + "/nosuchdir")
+end
+
+assert('Dir.foreach') do
+  a = []
+  Dir.foreach(DirTest.sandbox) { |s| a << s }
+  assert_true a.include? "a"
+  assert_true a.include? "b"
+end
+
+assert('Dir.getwd') do
+  s = Dir.getwd
+  assert_true s.kind_of? String
+end
+
+assert('Dir.mkdir') do
+  m1 = DirTest.sandbox + "/mkdir1"
+  m2 = DirTest.sandbox + "/mkdir2"
+  assert_equal 0, Dir.mkdir(m1)
+  assert_equal 0, Dir.mkdir(m2, 0765)
+end
+
+assert('Dir.delete') do
+  s = DirTest.sandbox + "/delete"
+  Dir.mkdir(s)
+  assert_true Dir.exist?(s)
+
+  Dir.delete(s)
+  assert_false Dir.exist?(s)
+end
+
+assert('Dir.open') do
+  a = []
+  Dir.open(DirTest.sandbox) { |d|
+    d.each { |s| a << s }
+  }
+  assert_true a.include? "a"
+  assert_true a.include? "b"
+end
+
+assert('Dir#initialize and Dir#close') do
+  d = Dir.new(".")
+  assert_true d.instance_of? Dir
+  assert_nil d.close
+end
+
+assert('Dir#close') do
+  d = Dir.new(".")
+end
+
+assert('Dir#each') do
+  a = []
+  d = Dir.open(DirTest.sandbox)
+  d.each { |s| a << s }
+  d.close
+  assert_true a.include? "a"
+  assert_true a.include? "b"
+end
+
+assert('Dir#read') do
+  a = []
+  d = Dir.open(DirTest.sandbox)
+  while s = d.read
+    a << s
+  end
+  d.close
+  assert_true a.include? "a"
+  assert_true a.include? "b"
+end
+
+assert('Dir#rewind') do
+  d = Dir.open(DirTest.sandbox)
+  while d.read; end
+
+  assert_equal d, d.rewind
+
+  a = []
+  while s = d.read
+    a << s
+  end
+  d.close
+  assert_true a.include? "a"
+  assert_true a.include? "b"
+end
+
+assert('DirTest.teardown') do
+  DirTest.teardown
+end
diff --git a/test/dirtest.c b/test/dirtest.c
new file mode 100644
index 000000000..ca5e9f19a
--- /dev/null
+++ b/test/dirtest.c
@@ -0,0 +1,114 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <dirent.h>
+#include <unistd.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "mruby.h"
+#include "mruby/string.h"
+#include "mruby/variable.h"
+
+
+mrb_value
+mrb_dirtest_setup(mrb_state *mrb, mrb_value klass)
+{
+  mrb_value s;
+  char buf[1024];
+  const char *aname = "a";
+  const char *bname = "b";
+
+  /* save current working directory */
+  if (getcwd(buf, sizeof(buf)) == NULL) {
+    mrb_raise(mrb, E_RUNTIME_ERROR, "getcwd() failed");
+  }
+  mrb_cv_set(mrb, klass, mrb_intern_cstr(mrb, "pwd"), mrb_str_new_cstr(mrb, buf));
+
+  /* create sandbox */
+  snprintf(buf, sizeof(buf), "%smruby-dir-test.XXXXXX", P_tmpdir);
+  if (mkdtemp(buf) == NULL) {
+    mrb_raisef(mrb, E_RUNTIME_ERROR, "mkdtemp(%S) failed", mrb_str_new_cstr(mrb, buf));
+  }
+  s = mrb_str_new_cstr(mrb, buf);
+  mrb_cv_set(mrb, klass, mrb_intern_cstr(mrb, "sandbox"), s);
+
+  /* go to sandbox */
+  if (chdir(buf) == -1) {
+    rmdir(buf);
+    mrb_raisef(mrb, E_RUNTIME_ERROR, "chdir(%S) failed", s);
+  }
+  
+  /* make some directories in the sandbox */
+  if (mkdir(aname, 0) == -1) {
+    chdir("..");
+    rmdir(buf);
+    mrb_raisef(mrb, E_RUNTIME_ERROR, "mkdir(%S) failed", mrb_str_new_cstr(mrb, aname));
+  }
+  if (mkdir(bname, 0) == -1) {
+    rmdir(aname);
+    chdir("..");
+    rmdir(buf);
+    mrb_raisef(mrb, E_RUNTIME_ERROR, "mkdir(%S) failed", mrb_str_new_cstr(mrb, bname));
+  }
+
+  return mrb_true_value();
+}
+
+mrb_value
+mrb_dirtest_teardown(mrb_state *mrb, mrb_value klass)
+{
+  mrb_value d, sandbox;
+  DIR *dirp;
+  struct dirent *dp;
+  const char *path;
+
+  /* cleanup sandbox */
+  sandbox = mrb_cv_get(mrb, klass, mrb_intern_cstr(mrb, "sandbox"));
+  path = mrb_str_to_cstr(mrb, sandbox);
+
+  dirp = opendir(path);
+  while ((dp = readdir(dirp)) != NULL) {
+    if (strcmp(dp->d_name, ".") == 0 || strcmp(dp->d_name, "..") == 0)
+      continue;
+    if (rmdir(dp->d_name) == -1) {
+      mrb_raisef(mrb, E_RUNTIME_ERROR, "rmdir(%S) failed", mrb_str_new_cstr(mrb, dp->d_name));
+    }
+  }
+  closedir(dirp);
+
+  /* back to original pwd */
+  d = mrb_cv_get(mrb, klass, mrb_intern_cstr(mrb, "pwd"));
+  path = mrb_str_to_cstr(mrb, d);
+  if (chdir(path) == -1) {
+    mrb_raisef(mrb, E_RUNTIME_ERROR, "chdir(%S) failed", d);
+  }
+
+  /* remove sandbox directory */
+  sandbox = mrb_cv_get(mrb, klass, mrb_intern_cstr(mrb, "sandbox"));
+  path = mrb_str_to_cstr(mrb, sandbox);
+  if (rmdir(path) == -1) {
+    mrb_raisef(mrb, E_RUNTIME_ERROR, "rmdir(%S) failed", sandbox);
+  }
+
+  return mrb_true_value();
+}
+
+mrb_value
+mrb_dirtest_sandbox(mrb_state *mrb, mrb_value klass)
+{
+  return mrb_cv_get(mrb, klass, mrb_intern_cstr(mrb, "sandbox"));
+}
+
+void
+mrb_mruby_dir_gem_test(mrb_state *mrb)
+{
+  struct RClass *c = mrb_define_module(mrb, "DirTest");
+
+  mrb_define_class_method(mrb, c, "sandbox", mrb_dirtest_sandbox, MRB_ARGS_NONE());
+  mrb_define_class_method(mrb, c, "setup", mrb_dirtest_setup, MRB_ARGS_NONE());
+  mrb_define_class_method(mrb, c, "teardown", mrb_dirtest_teardown, MRB_ARGS_NONE());
+}
+