diff --git a/base/tests/TestThreads.cpp b/base/tests/TestThreads.cpp
new file mode 100644
index 000000000000..a9dc3c4b37a6
--- /dev/null
+++ b/base/tests/TestThreads.cpp
@@ -0,0 +1,141 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "NPL"); you may not use this file except in
+ * compliance with the NPL.  You may obtain a copy of the NPL at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the NPL is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
+ * for the specific language governing rights and limitations under the
+ * NPL.
+ *
+ * The Initial Developer of this code under the NPL is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
+ * Reserved.
+ */
+
+#include "nsIThread.h"
+#include <stdio.h>
+
+class nsRunner : public nsIRunnable {
+public:
+    NS_DECL_ISUPPORTS
+
+    NS_IMETHOD Run() {
+        printf("running %d\n", mNum);
+        nsIThread* thread;
+        nsresult rv = nsIThread::GetCurrent(&thread);
+        if (NS_FAILED(rv)) {
+            printf("failed to get current thread\n");
+            return rv;
+        }
+        NS_RELEASE(thread);
+
+        // if we don't do something slow, we'll never see the other
+        // worker threads run
+        PR_Sleep(100);
+
+        return rv;
+    }
+
+    nsRunner(int num) : mNum(num) {
+        NS_INIT_REFCNT();
+    }
+
+protected:
+    int mNum;
+};
+
+NS_IMPL_ISUPPORTS(nsRunner, nsIRunnable::GetIID());
+
+nsresult
+TestThreads()
+{
+    nsresult rv;
+
+    nsIThread* runner;
+    rv = NS_NewThread(&runner, new nsRunner(0));
+    if (NS_FAILED(rv)) {
+        printf("failed to create thread\n");
+        return rv;
+    }
+
+    nsIThread* thread;
+    rv = nsIThread::GetCurrent(&thread);
+    if (NS_FAILED(rv)) {
+        printf("failed to get current thread\n");
+        return rv;
+    }
+
+    PRThreadScope scope;
+    rv = runner->GetScope(&scope);
+    if (NS_FAILED(rv)) {
+        printf("runner already exited\n");        
+    }
+
+    rv = runner->Join();     // wait for the runner to die before quitting
+    if (NS_FAILED(rv)) {
+        printf("join failed\n");        
+    }
+
+    rv = runner->GetScope(&scope);      // this should fail after Join
+    if (NS_SUCCEEDED(rv)) {
+        printf("get scope failed\n");        
+    }
+
+    rv = runner->Interrupt();   // this should fail after Join
+    if (NS_SUCCEEDED(rv)) {
+        printf("interrupt failed\n");        
+    }
+
+    NS_RELEASE(runner);
+    NS_RELEASE(thread);
+
+    ////////////////////////////////////////////////////////////////////////////
+    // try an unjoinable thread 
+    rv = NS_NewThread(&runner, new nsRunner(1), 0, PR_USER_THREAD,
+                      PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD, PR_UNJOINABLE_THREAD);
+    if (NS_FAILED(rv)) {
+        printf("failed to create thread\n");
+        return rv;
+    }
+
+    rv = runner->Join();     // wait for the runner to die before quitting
+    if (NS_SUCCEEDED(rv)) {
+        printf("shouldn't have been able to join an unjoinable thread\n");        
+    }
+    NS_RELEASE(runner);
+
+    return NS_OK;
+}
+
+nsresult
+TestThreadPools()
+{
+    nsIThreadPool* pool;
+    nsresult rv = NS_NewThreadPool(&pool, 4, 4);
+    if (NS_FAILED(rv)) {
+        printf("failed to create thead pool\n");
+        return rv;
+    }
+
+    for (PRUint32 i = 0; i < 100; i++) {
+        rv = pool->DispatchRequest(new nsRunner(i+2));
+    }
+    rv = pool->Join();
+    return rv;
+}
+
+int
+main()
+{
+    nsresult rv = TestThreads();
+    if (NS_FAILED(rv)) return -1;
+
+    rv = TestThreadPools();
+    if (NS_FAILED(rv)) return -1;
+
+    return 0;
+}
diff --git a/base/tests/makefile.win b/base/tests/makefile.win
index 084aedbd064b..ae7dc770356f 100644
--- a/base/tests/makefile.win
+++ b/base/tests/makefile.win
@@ -25,6 +25,7 @@ PROG3 = .\$(OBJDIR)\TestCRT.exe
 PROG4 = .\$(OBJDIR)\FilesTest.exe
 PROG5 = .\$(OBJDIR)\PropertiesTest.exe
 PROG6 = .\$(OBJDIR)\TestAutoLock.exe
+PROG7 = .\$(OBJDIR)\TestThreads.exe
 RESFILE = timer.res
 PROGRAMS = $(PROG0) $(PROG1) \
 !ifdef MODULAR_NETLIB
@@ -34,6 +35,7 @@ PROGRAMS = $(PROG0) $(PROG1) \
 !endif
 	$(PROG4) \
         $(PROG6) \
+        $(PROG7) \
 	$(NULL)
 
 LINCS=-I..\src -I$(PUBLIC)\xpcom -I$(PUBLIC)\netlib -I$(PUBLIC)\raptor
@@ -64,6 +66,7 @@ install:: $(PROGRAMS)
 !endif
 	$(MAKE_INSTALL) $(PROG4) $(DIST)\bin
         $(MAKE_INSTALL) $(PROG6) $(DIST)\bin
+        $(MAKE_INSTALL) $(PROG7) $(DIST)\bin
 
 clobber::
 	rm -f $(DIST)\bin\TimerTest.exe
@@ -109,4 +112,6 @@ $(PROG5): $(OBJDIR) PropertiesTest.cpp
 
 $(PROG6): $(OBJDIR) TestAutoLock.cpp
 
+$(PROG7): $(OBJDIR) TestThreads.cpp
+
 
diff --git a/xpcom/tests/TestThreads.cpp b/xpcom/tests/TestThreads.cpp
new file mode 100644
index 000000000000..a9dc3c4b37a6
--- /dev/null
+++ b/xpcom/tests/TestThreads.cpp
@@ -0,0 +1,141 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "NPL"); you may not use this file except in
+ * compliance with the NPL.  You may obtain a copy of the NPL at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the NPL is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
+ * for the specific language governing rights and limitations under the
+ * NPL.
+ *
+ * The Initial Developer of this code under the NPL is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
+ * Reserved.
+ */
+
+#include "nsIThread.h"
+#include <stdio.h>
+
+class nsRunner : public nsIRunnable {
+public:
+    NS_DECL_ISUPPORTS
+
+    NS_IMETHOD Run() {
+        printf("running %d\n", mNum);
+        nsIThread* thread;
+        nsresult rv = nsIThread::GetCurrent(&thread);
+        if (NS_FAILED(rv)) {
+            printf("failed to get current thread\n");
+            return rv;
+        }
+        NS_RELEASE(thread);
+
+        // if we don't do something slow, we'll never see the other
+        // worker threads run
+        PR_Sleep(100);
+
+        return rv;
+    }
+
+    nsRunner(int num) : mNum(num) {
+        NS_INIT_REFCNT();
+    }
+
+protected:
+    int mNum;
+};
+
+NS_IMPL_ISUPPORTS(nsRunner, nsIRunnable::GetIID());
+
+nsresult
+TestThreads()
+{
+    nsresult rv;
+
+    nsIThread* runner;
+    rv = NS_NewThread(&runner, new nsRunner(0));
+    if (NS_FAILED(rv)) {
+        printf("failed to create thread\n");
+        return rv;
+    }
+
+    nsIThread* thread;
+    rv = nsIThread::GetCurrent(&thread);
+    if (NS_FAILED(rv)) {
+        printf("failed to get current thread\n");
+        return rv;
+    }
+
+    PRThreadScope scope;
+    rv = runner->GetScope(&scope);
+    if (NS_FAILED(rv)) {
+        printf("runner already exited\n");        
+    }
+
+    rv = runner->Join();     // wait for the runner to die before quitting
+    if (NS_FAILED(rv)) {
+        printf("join failed\n");        
+    }
+
+    rv = runner->GetScope(&scope);      // this should fail after Join
+    if (NS_SUCCEEDED(rv)) {
+        printf("get scope failed\n");        
+    }
+
+    rv = runner->Interrupt();   // this should fail after Join
+    if (NS_SUCCEEDED(rv)) {
+        printf("interrupt failed\n");        
+    }
+
+    NS_RELEASE(runner);
+    NS_RELEASE(thread);
+
+    ////////////////////////////////////////////////////////////////////////////
+    // try an unjoinable thread 
+    rv = NS_NewThread(&runner, new nsRunner(1), 0, PR_USER_THREAD,
+                      PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD, PR_UNJOINABLE_THREAD);
+    if (NS_FAILED(rv)) {
+        printf("failed to create thread\n");
+        return rv;
+    }
+
+    rv = runner->Join();     // wait for the runner to die before quitting
+    if (NS_SUCCEEDED(rv)) {
+        printf("shouldn't have been able to join an unjoinable thread\n");        
+    }
+    NS_RELEASE(runner);
+
+    return NS_OK;
+}
+
+nsresult
+TestThreadPools()
+{
+    nsIThreadPool* pool;
+    nsresult rv = NS_NewThreadPool(&pool, 4, 4);
+    if (NS_FAILED(rv)) {
+        printf("failed to create thead pool\n");
+        return rv;
+    }
+
+    for (PRUint32 i = 0; i < 100; i++) {
+        rv = pool->DispatchRequest(new nsRunner(i+2));
+    }
+    rv = pool->Join();
+    return rv;
+}
+
+int
+main()
+{
+    nsresult rv = TestThreads();
+    if (NS_FAILED(rv)) return -1;
+
+    rv = TestThreadPools();
+    if (NS_FAILED(rv)) return -1;
+
+    return 0;
+}