diff --git a/test/socket/test_ancdata.rb b/test/socket/test_ancdata.rb
new file mode 100644
index 0000000000..f0ce09638f
--- /dev/null
+++ b/test/socket/test_ancdata.rb
@@ -0,0 +1,56 @@
+require 'test/unit'
+require 'socket'
+
+class TestSocketAncData < Test::Unit::TestCase
+  def test_int
+    ancdata = Socket::AncillaryData.int(0, 0, 0, 123)
+    assert_equal(123, ancdata.int)
+    assert_equal([123].pack("i"), ancdata.data)
+  end
+
+  def test_ip_pktinfo
+    addr = Addrinfo.ip("127.0.0.1")
+    ifindex = 0
+    spec_dst = Addrinfo.ip("127.0.0.2")
+    begin
+      ancdata = Socket::AncillaryData.ip_pktinfo(addr, ifindex, spec_dst)
+    rescue NotImplementedError
+      return
+    end
+    assert_equal(Socket::AF_INET, ancdata.family)
+    assert_equal(Socket::IPPROTO_IP, ancdata.level)
+    assert_equal(Socket::IP_PKTINFO, ancdata.type)
+    assert_equal(addr.ip_address, ancdata.ip_pktinfo[0].ip_address)
+    assert_equal(ifindex, ancdata.ip_pktinfo[1])
+    assert_equal(spec_dst.ip_address, ancdata.ip_pktinfo[2].ip_address)
+    assert(ancdata.cmsg_is?(:IP, :PKTINFO))
+    assert(ancdata.cmsg_is?("IP", "PKTINFO"))
+    assert(ancdata.cmsg_is?(Socket::IPPROTO_IP, Socket::IP_PKTINFO))
+    if defined? Socket::IPV6_PKTINFO
+      assert(!ancdata.cmsg_is?(:IPV6, :PKTINFO))
+    end
+  end
+
+  def test_ipv6_pktinfo
+    addr = Addrinfo.ip("::1")
+    ifindex = 0
+    begin
+      ancdata = Socket::AncillaryData.ipv6_pktinfo(addr, ifindex)
+    rescue NotImplementedError
+      return
+    end
+    assert_equal(Socket::AF_INET6, ancdata.family)
+    assert_equal(Socket::IPPROTO_IPV6, ancdata.level)
+    assert_equal(Socket::IPV6_PKTINFO, ancdata.type)
+    assert_equal(addr.ip_address, ancdata.ipv6_pktinfo[0].ip_address)
+    assert_equal(ifindex, ancdata.ipv6_pktinfo[1])
+    assert_equal(addr.ip_address, ancdata.ipv6_pktinfo_addr.ip_address)
+    assert_equal(ifindex, ancdata.ipv6_pktinfo_ifindex)
+    assert(ancdata.cmsg_is?(:IPV6, :PKTINFO))
+    assert(ancdata.cmsg_is?("IPV6", "PKTINFO"))
+    assert(ancdata.cmsg_is?(Socket::IPPROTO_IPV6, Socket::IPV6_PKTINFO))
+    if defined? Socket::IP_PKTINFO
+      assert(!ancdata.cmsg_is?(:IP, :PKTINFO))
+    end
+  end
+end