diff --git a/test/ruby/test_system.rb b/test/ruby/test_system.rb
index 8c31f0a1b8..0db6618104 100644
--- a/test/ruby/test_system.rb
+++ b/test/ruby/test_system.rb
@@ -15,48 +15,50 @@ class TestSystem < Test::Unit::TestCase
     assert_equal("foobar\n", `echo foobar`)
     assert_equal('foobar', `#{ruby} -e 'print "foobar"'`)
 
-    tmpfilename = "#{Dir.tmpdir}/ruby_script_tmp.#{$$}"
+    Dir.mktmpdir("ruby_script_tmp") {|tmpdir|
+      tmpfilename = "#{tmpdir}/ruby_script_tmp.#{$$}"
 
-    tmp = open(tmpfilename, "w")
-    tmp.print "print $zzz\n";
-    tmp.close
+      tmp = open(tmpfilename, "w")
+      tmp.print "print $zzz\n";
+      tmp.close
 
-    assert_equal('true', `#{ruby} -s #{tmpfilename} -zzz`)
-    assert_equal('555', `#{ruby} -s #{tmpfilename} -zzz=555`)
+      assert_equal('true', `#{ruby} -s #{tmpfilename} -zzz`)
+      assert_equal('555', `#{ruby} -s #{tmpfilename} -zzz=555`)
 
-    tmp = open(tmpfilename, "w")
-    tmp.print "#! /usr/local/bin/ruby -s\n";
-    tmp.print "print $zzz\n";
-    tmp.close
+      tmp = open(tmpfilename, "w")
+      tmp.print "#! /usr/local/bin/ruby -s\n";
+      tmp.print "print $zzz\n";
+      tmp.close
 
-    assert_equal('678', `#{ruby} #{tmpfilename} -zzz=678`)
+      assert_equal('678', `#{ruby} #{tmpfilename} -zzz=678`)
 
-    tmp = open(tmpfilename, "w")
-    tmp.print "this is a leading junk\n";
-    tmp.print "#! /usr/local/bin/ruby -s\n";
-    tmp.print "print $zzz\n";
-    tmp.print "__END__\n";
-    tmp.print "this is a trailing junk\n";
-    tmp.close
+      tmp = open(tmpfilename, "w")
+      tmp.print "this is a leading junk\n";
+      tmp.print "#! /usr/local/bin/ruby -s\n";
+      tmp.print "print $zzz\n";
+      tmp.print "__END__\n";
+      tmp.print "this is a trailing junk\n";
+      tmp.close
 
-    assert_equal('', `#{ruby} -x #{tmpfilename}`)
-    assert_equal('555', `#{ruby} -x #{tmpfilename} -zzz=555`)
+      assert_equal('', `#{ruby} -x #{tmpfilename}`)
+      assert_equal('555', `#{ruby} -x #{tmpfilename} -zzz=555`)
 
-    tmp = open(tmpfilename, "w")
-    for i in 1..5
-      tmp.print i, "\n"
-    end
-    tmp.close
+      tmp = open(tmpfilename, "w")
+      for i in 1..5
+        tmp.print i, "\n"
+      end
+      tmp.close
 
-    `#{ruby} -i.bak -pe '$_.sub!(/^[0-9]+$/){$&.to_i * 5}' #{tmpfilename}`
-    tmp = open(tmpfilename, "r")
-    while tmp.gets
-      assert_equal(0, $_.to_i % 5)
-    end
-    tmp.close
+      `#{ruby} -i.bak -pe '$_.sub!(/^[0-9]+$/){$&.to_i * 5}' #{tmpfilename}`
+      tmp = open(tmpfilename, "r")
+      while tmp.gets
+        assert_equal(0, $_.to_i % 5)
+      end
+      tmp.close
 
-    File.unlink tmpfilename or `/bin/rm -f "#{tmpfilename}"`
-    File.unlink "#{tmpfilename}.bak" or `/bin/rm -f "#{tmpfilename}.bak"`
+      File.unlink tmpfilename or `/bin/rm -f "#{tmpfilename}"`
+      File.unlink "#{tmpfilename}.bak" or `/bin/rm -f "#{tmpfilename}.bak"`
+    }
   end
 
   def test_syntax
diff --git a/test/ruby/test_whileuntil.rb b/test/ruby/test_whileuntil.rb
index 5e8ce4b211..df5bda450d 100644
--- a/test/ruby/test_whileuntil.rb
+++ b/test/ruby/test_whileuntil.rb
@@ -3,71 +3,73 @@ require 'tmpdir'
 
 class TestWhileuntil < Test::Unit::TestCase
   def test_while
-    tmpfilename = "#{Dir.tmpdir}/ruby_while_tmp.#{$$}"
+    Dir.mktmpdir("ruby_while_tmp") {|tmpdir|
+      tmpfilename = "#{tmpdir}/ruby_while_tmp.#{$$}"
 
-    tmp = open(tmpfilename, "w")
-    tmp.print "tvi925\n";
-    tmp.print "tvi920\n";
-    tmp.print "vt100\n";
-    tmp.print "Amiga\n";
-    tmp.print "paper\n";
-    tmp.close
+      tmp = open(tmpfilename, "w")
+      tmp.print "tvi925\n";
+      tmp.print "tvi920\n";
+      tmp.print "vt100\n";
+      tmp.print "Amiga\n";
+      tmp.print "paper\n";
+      tmp.close
 
-    tmp = open(tmpfilename, "r")
-    assert_instance_of(File, tmp)
-    
-    while line = tmp.gets()
-      break if /vt100/ =~ line
-    end
-
-    assert(!tmp.eof?)
-    assert_match(/vt100/, line)
-    tmp.close
-
-    tmp = open(tmpfilename, "r")
-    while line = tmp.gets()
-      next if /vt100/ =~ line
-      assert_no_match(/vt100/, line)
-    end
-    assert(tmp.eof?)
-    assert_no_match(/vt100/, line)
-    tmp.close
-
-    tmp = open(tmpfilename, "r")
-    while line = tmp.gets()
-      lastline = line
-      line = line.gsub(/vt100/, 'VT100')
-      if lastline != line
-        line.gsub!('VT100', 'Vt100')
-        redo
+      tmp = open(tmpfilename, "r")
+      assert_instance_of(File, tmp)
+      
+      while line = tmp.gets()
+        break if /vt100/ =~ line
       end
-      assert_no_match(/vt100/, line)
-      assert_no_match(/VT100/, line)
-    end
-    assert(tmp.eof?)
-    tmp.close
 
-    sum=0
-    for i in 1..10
-      sum += i
-      i -= 1
-      if i > 0
-        redo
+      assert(!tmp.eof?)
+      assert_match(/vt100/, line)
+      tmp.close
+
+      tmp = open(tmpfilename, "r")
+      while line = tmp.gets()
+        next if /vt100/ =~ line
+        assert_no_match(/vt100/, line)
       end
-    end
-    assert_equal(220, sum)
-
-    tmp = open(tmpfilename, "r")
-    while line = tmp.gets()
-      break if 3
+      assert(tmp.eof?)
       assert_no_match(/vt100/, line)
-      assert_no_match(/Amiga/, line)
-      assert_no_match(/paper/, line)
-    end
-    tmp.close
+      tmp.close
 
-    File.unlink tmpfilename or `/bin/rm -f "#{tmpfilename}"`
-    assert(!File.exist?(tmpfilename))
+      tmp = open(tmpfilename, "r")
+      while line = tmp.gets()
+        lastline = line
+        line = line.gsub(/vt100/, 'VT100')
+        if lastline != line
+          line.gsub!('VT100', 'Vt100')
+          redo
+        end
+        assert_no_match(/vt100/, line)
+        assert_no_match(/VT100/, line)
+      end
+      assert(tmp.eof?)
+      tmp.close
+
+      sum=0
+      for i in 1..10
+        sum += i
+        i -= 1
+        if i > 0
+          redo
+        end
+      end
+      assert_equal(220, sum)
+
+      tmp = open(tmpfilename, "r")
+      while line = tmp.gets()
+        break if 3
+        assert_no_match(/vt100/, line)
+        assert_no_match(/Amiga/, line)
+        assert_no_match(/paper/, line)
+      end
+      tmp.close
+
+      File.unlink tmpfilename or `/bin/rm -f "#{tmpfilename}"`
+      assert(!File.exist?(tmpfilename))
+    }
   end
 
   def test_until
diff --git a/test/scanf/test_scanf.rb b/test/scanf/test_scanf.rb
index 2890a3a038..d2e7aa988f 100644
--- a/test/scanf/test_scanf.rb
+++ b/test/scanf/test_scanf.rb
@@ -297,7 +297,7 @@ class TestIOScanf
   include Scanf
   extend ScanfTests
 
-  tmpfilename = "#{Dir.tmpdir}/iotest.dat"
+  tmpfilename = "#{Dir.tmpdir}/iotest.dat.#{$$}"
   
   i = 1
   self.tests.each do |test|
diff --git a/test/scanf/test_scanfblocks.rb b/test/scanf/test_scanfblocks.rb
index 7048ae1bf7..907a3c2838 100644
--- a/test/scanf/test_scanfblocks.rb
+++ b/test/scanf/test_scanfblocks.rb
@@ -50,8 +50,9 @@ alias set_up setup
   end
 
   def test_io1
-    File.open("#{Dir.tmpdir}/iotest.dat", "w") { |fh| fh.puts(@str) }
-    fh = File.open("#{Dir.tmpdir}/iotest.dat", "rb")
+    fn = "#{Dir.tmpdir}/iotest.dat.#{$$}"
+    File.open(fn, "w") { |fh| fh.puts(@str) }
+    fh = File.open(fn, "rb")
     res = fh.scanf("%s%d") { |name, year| "#{name} was born in #{year}." }
 
     assert_equal(
@@ -62,18 +63,19 @@ alias set_up setup
       "Brahms was born in 1833." ],res)
     fh.close
   ensure
-    File.delete("#{Dir.tmpdir}/iotest.dat")  
-    end
+    File.delete(fn)  
+  end
 
   def test_io2
-    File.open("#{Dir.tmpdir}/iotest.dat", "w").close
-    fh = File.open("#{Dir.tmpdir}/iotest.dat","rb")
+    fn = "#{Dir.tmpdir}/iotest.dat.#{$$}"
+    File.open(fn, "w").close
+    fh = File.open(fn,"rb")
     assert_equal(fh.scanf("") {}, [])
     fh.seek(0)
     assert_equal(fh.scanf("%d%f%s") {}, [])
     fh.close
   ensure
-    File.delete("#{Dir.tmpdir}/iotest.dat")  
+    File.delete(fn)  
   end
 
 end