diff --git a/test/io/nonblock/test_flush.rb b/test/io/nonblock/test_flush.rb
index 4f56d00829..40dbe94b3a 100644
--- a/test/io/nonblock/test_flush.rb
+++ b/test/io/nonblock/test_flush.rb
@@ -23,7 +23,7 @@ class TestIONonblock < Test::Unit::TestCase
       end
     }
     assert_raise(IOError) {w.flush}
-    t.join
-    assert_equal("b", result)
+    assert_nothing_raised {t.join}
+    assert_equal(4097, result.size)
   end
 end if IO.method_defined?(:nonblock)
diff --git a/test/ruby/test_super.rb b/test/ruby/test_super.rb
index ec0f8b608e..16b623df61 100644
--- a/test/ruby/test_super.rb
+++ b/test/ruby/test_super.rb
@@ -65,4 +65,24 @@ class TestSuper < Test::Unit::TestCase
     assert_equal([1,2,3], Array4.new.array(1, 2, 3))
     assert_equal([1,2,3,4], Array4.new.array(1, 2, 3, 4))
   end
+
+  class A
+    def tt(aa)
+      "A#tt"
+    end
+
+    def uu(a)
+      class << self
+        define_method(:tt) do |sym|
+          super
+        end
+      end
+    end
+  end
+
+  def test_define_method # [ruby-core:03856]
+    a = A.new
+    a.uu(12)
+    assert_raise(RuntimeError) {a.tt(12)}
+  end
 end
diff --git a/test/socket/test_tcp.rb b/test/socket/test_tcp.rb
index e059621985..8d55c011cf 100644
--- a/test/socket/test_tcp.rb
+++ b/test/socket/test_tcp.rb
@@ -7,17 +7,22 @@ end
 
 class TestTCPSocket < Test::Unit::TestCase
   def test_recvfrom # [ruby-dev:24705]
+    c = s = nil
     svr = TCPServer.new("localhost", 0)
     Thread.new {
-      svr.accept.print("x"*0x1000)
+      c = svr.accept
+      Thread.pass until s
+      c.print("x"*0x1000)
     }
     addr = svr.addr
     sock = TCPSocket.open(addr[2], addr[1])
     Thread.new {
-      Thread.pass
+      Thread.pass until c
+      Thread.critical = true
       ObjectSpace.each_object(String) {|s|
-        s.replace "a" if s.length == 0x10000
+        s.replace "a" if s.length == 0x10000 and !s.frozen?
       }
+      Thread.critical = false
     }
     assert_raise(RuntimeError, SocketError) {
       sock.recvfrom(0x10000)