diff --git a/mps/code/comm.gmk b/mps/code/comm.gmk
index e8e5bb6383b..43d9962bf1f 100644
--- a/mps/code/comm.gmk
+++ b/mps/code/comm.gmk
@@ -273,7 +273,8 @@ all: mpmss sacss amcss amcsshe amsss amssshe segsmss awlut awluthe \
      mpsicv lockcov poolncv locv qs apss \
      finalcv fin1658a finaltest arenacv bttest teletest \
      abqtest cbstest btcv mv2test messtest steptest \
-     eventcnv walkt0 libcbt \
+     walkt0 libcbt z001989a \
+     eventcnv \
      mps.a mpsplan.a
 
 swall: mmsw.a replaysw
@@ -303,6 +304,7 @@ mpmss sacss amcss amcssth amcsshe amsss amssshe segsmss awlut awlutth \
   messtest steptest \
   walkt0 \
   exposet0 \
+  z001989a \
   eventcnv replay replaysw \
   mps.a mmsw.a mpsplan.a mmdw.a: phony
 ifdef VARIETY
@@ -456,6 +458,9 @@ $(PFM)/$(VARIETY)/walkt0: $(PFM)/$(VARIETY)/walkt0.o \
 $(PFM)/$(VARIETY)/exposet0: $(PFM)/$(VARIETY)/exposet0.o \
 	$(FMTDYTSTOBJ) $(MPMOBJ) $(PLINTHOBJ) $(AMCOBJ) $(TESTLIBOBJ)
 
+$(PFM)/$(VARIETY)/z001989a: $(PFM)/$(VARIETY)/z001989a.o \
+	$(FMTDYTSTOBJ) $(MPMOBJ) $(PLINTHOBJ) $(AMCOBJ) $(TESTLIBOBJ)
+
 $(PFM)/$(VARIETY)/eventcnv: $(PFM)/$(VARIETY)/eventcnv.o \
   $(PFM)/$(VARIETY)/eventpro.o $(PFM)/$(VARIETY)/table.o
 
diff --git a/mps/code/commpost.nmk b/mps/code/commpost.nmk
index 641b5d8b1df..d8670151944 100644
--- a/mps/code/commpost.nmk
+++ b/mps/code/commpost.nmk
@@ -19,7 +19,7 @@ all: mpmss.exe amcss.exe amsss.exe amssshe.exe segsmss.exe awlut.exe awluthe.exe
      finalcv.exe fin1658a.exe finaltest.exe \
      arenacv.exe bttest.exe teletest.exe \
      abqtest.exe cbstest.exe btcv.exe mv2test.exe messtest.exe steptest.exe \
-     locbwcss.exe locusss.exe \
+     locbwcss.exe locusss.exe z001989a.exe \
      eventcnv.exe \
      mps.lib mpsplan.lib
 
@@ -38,7 +38,7 @@ mpmss.exe amcss.exe amcsshe.exe amsss.exe amssshe.exe segsmss.exe awlut.exe awlu
      expt825.exe \
      abqtest.exe cbstest.exe btcv.exe mv2test.exe messtest.exe steptest.exe \
      walkt0.exe locbwcss.exe locusss.exe \
-     exposet0.exe \
+     exposet0.exe z001989a.exe \
      replay.exe replaysw.exe eventcnv.exe \
      mmdw.lib mmsw.lib mps.lib mpsplan.lib mpsplcb.lib \
      mpsdy.dll:
@@ -212,6 +212,10 @@ $(PFM)\$(VARIETY)\btcv.exe: $(PFM)\$(VARIETY)\btcv.obj \
 $(PFM)\$(VARIETY)\mv2test.exe: $(PFM)\$(VARIETY)\mv2test.obj \
 	$(MPMOBJ) $(PLINTHOBJ) $(TESTLIBOBJ)
 
+$(PFM)\$(VARIETY)\z001989a.exe: $(PFM)\$(VARIETY)\z001989a.obj \
+	$(MPMOBJ) $(PLINTHOBJ) $(AMCOBJ) $(FMTTESTOBJ) \
+	$(MRGOBJ) $(TESTLIBOBJ)
+
 $(PFM)\$(VARIETY)\eventcnv.exe: $(PFM)\$(VARIETY)\eventcnv.obj \
 	$(PFM)\$(VARIETY)\eventpro.obj $(PFM)\$(VARIETY)\table.obj
 
diff --git a/mps/code/z001989a.c b/mps/code/z001989a.c
index 3ba4621486f..8a7f27d1f5b 100644
--- a/mps/code/z001989a.c
+++ b/mps/code/z001989a.c
@@ -1,12 +1,50 @@
-/* fin1658a.c: Test for suspected defect described in job001658
+/* z001989a.c: Test for defect described in job001989
  *
  * $Id$
- * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ * Copyright (c) 2008 Ravenbrook Limited.  See end of file for license.
  * Portions copyright (C) 2002 Global Graphics Software.
  *
- * DESIGN
+ * OBJECTIVE
  *
- * See <design/poolmrg/#test>.
+ * Show that MPS messages are correct regardless of when the client 
+ * gets them.  (Note: "get" means "mps_message_get", throughout).
+ *
+ * DESIGN OVERVIEW
+ *
+ * Client (this test) does various actions that are known to provoke 
+ * MPS messages.  Client (this test) gets these messages at variable 
+ * times.
+ *
+ * Verification is:
+ *   - client gets all the expected messages, and no others, at the 
+ *     expected time;
+ *   - no asserts or failures.
+ *
+ * Additionally: client checks the message order.  MPS specification 
+ * does not currently guarantee that messages are queued in order of 
+ * posting, but in fact they should be, and it is a useful check.
+ * (But finalization messages from a single collection may be posted 
+ * in any order).
+ *
+ * The actions, messages to check for, and get times, are scripted 
+ * using a simple text code:
+ *   C - action: request garbage-collection;
+ *   F - action: make a (registered)finalized object unreachable;
+ *   b - message produced: collection begin (mps_message_type_gc_start);
+ *   e - message produced: collection end (mps_message_type_gc);
+ *   f - message produced: finalization (mps_message_type_finalization);
+ *   . - get messages.
+ *
+ * Example:
+ *  script "Cbe.FFCbffe.Cbe"
+ *  means:
+ *    Requests a collection and checks for _gc_start and _gc messages
+ *    (in that order, and no other messages).  Then drops refs to two 
+ *    objects, requests another collection, and checks for _gc_start, 
+ *    the two finalization messages (in either order), and _gc.  Then 
+ *    Requests a third collection and ends the test WITHOUT GETTING 
+ *    the last two messages (note: no "."), to test that 
+ *    mps_arena_destroy copes with ungot messages.
  *
  * DEPENDENCIES
  *
@@ -15,7 +53,12 @@
  *
  * NOTES
  *
- * This code was created by first copying <code/finalcv.c>.
+ * This code was created by first copying <code/fin1658a.c>.
+ * Future: actions could be expanded to include:
+ *   - mps_arena_start_collect;
+ *   - mps_arena_step;
+ *   - automatic (not client-requested) collections.
+ * etc.
  */
 
 #include "testlib.h"
@@ -95,13 +138,103 @@ static void report(mps_arena_t arena, int expect)
 }
 
 
+/* testscript -- runs a test script
+ *
+ */
+static void testscript(mps_arena_t arena, const char *script)
+{
+  int N = myrootCOUNT - 1;
+  const char *scriptAll = script;
+  char am[10];  /* Array of Messages (expected but not yet got) */
+  char *pmNext = am;  /* Pointer to where Next Message will be stored */
+  
+  printf("Script: \"%s\"\n", script);
+
+  while(*script != '\0') {
+    switch(*script) {
+      case '.': {
+        *pmNext = '\0';
+        printf("  Getting messages (expecting \"%s\")...\n", am);
+        report(arena, pmNext - am);
+        printf("  ...done.\n");
+        pmNext = am;
+        break;
+      }
+      case 'C': {
+        printf("  Collect\n");
+        mps_arena_collect(arena);
+        break;
+      }
+      case 'F': {
+        /* make 0 and N finalizable */
+        myroot[0] = NULL;
+        state[0] = finalizableSTATE;
+        myroot[N] = NULL;
+        state[N] = finalizableSTATE;
+        mps_arena_collect(arena);
+        report(arena, 2);
+
+        mps_arena_collect(arena);
+        report(arena, 0);
+
+        /* make 1 and N-1 refer to each other and finalizable */
+        DYLAN_VECTOR_SLOT(myroot[1]  , 1) = (mps_word_t)myroot[N-1];
+        DYLAN_VECTOR_SLOT(myroot[N-1], 1) = (mps_word_t)myroot[1];
+        myroot[1] = NULL;
+        state[1] = finalizableSTATE;
+        myroot[N-1] = NULL;
+        state[N-1] = finalizableSTATE;
+        mps_arena_collect(arena);
+        report(arena, 2);
+
+        break;
+      }
+      case 'b': {
+        *pmNext++ = *script;
+        break;
+      }
+      case 'e': {
+        *pmNext++ = *script;
+        break;
+      }
+      default: {
+        printf("unknown script command %c (script %s).\n",
+               *script, scriptAll);
+        cdie(FALSE, "unknown script command");
+        return;
+      }
+    }
+    Insist(pmNext - am < NELEMS(am));
+    script++;
+  }
+}
+
+
+/* test -- runs various test scripts
+ *
+ */
+static void test(mps_arena_t arena)
+{
+  testscript(arena, ".");
+  testscript(arena, "C.");
+  testscript(arena, "CCC");
+  testscript(arena, "");
+  testscript(arena, ".");
+}
+
+
+/* main2 -- create pools and objects, then call test
+ *
+ * Is called via mps_tramp, so matches mps_tramp_t function prototype,
+ * and use trampDataStruct to pass parameters.
+ */
+
 typedef struct trampDataStruct {
   mps_arena_t arena;
   mps_thr_t thr;
 } trampDataStruct;
 
-
-static void *test(void *arg, size_t s)
+static void *main2(void *arg, size_t s)
 {
   trampDataStruct trampData;
   mps_arena_t arena;
@@ -113,7 +246,6 @@ static void *test(void *arg, size_t s)
   mps_ap_t ap;
   mps_root_t root_stackreg;
   int i;
-  int N = myrootCOUNT - 1;
   void *stack_starts_here;  /* stack scanning starts here */
 
   trampData = *(trampDataStruct*)arg;
@@ -151,36 +283,13 @@ static void *test(void *arg, size_t s)
   /* stop stack scanning, to prevent unwanted object retention */
   mps_root_destroy(root_stackreg);
 
+#if 0
+  mps_message_type_enable(arena, mps_message_type_gc_start());
+  mps_message_type_enable(arena, mps_message_type_gc());
+#endif
   mps_message_type_enable(arena, mps_message_type_finalization());
 
-  mps_arena_collect(arena);
-  report(arena, 0);
-
-  /* make 0 and N finalizable */
-  myroot[0] = NULL;
-  state[0] = finalizableSTATE;
-  myroot[N] = NULL;
-  state[N] = finalizableSTATE;
-  mps_arena_collect(arena);
-  report(arena, 2);
-
-  mps_arena_collect(arena);
-  report(arena, 0);
-
-  /* make 1 and N-1 refer to each other and finalizable */
-  DYLAN_VECTOR_SLOT(myroot[1]  , 1) = (mps_word_t)myroot[N-1];
-  DYLAN_VECTOR_SLOT(myroot[N-1], 1) = (mps_word_t)myroot[1];
-  myroot[1] = NULL;
-  state[1] = finalizableSTATE;
-  myroot[N-1] = NULL;
-  state[N-1] = finalizableSTATE;
-  mps_arena_collect(arena);
-  report(arena, 2);
-
-  mps_arena_collect(arena);
-  report(arena, 0);
-
-  /* @@@@ <design/poolmrg/#test.promise.ut.nofinal.check> missing */
+  test(arena);
 
   mps_ap_destroy(ap);
   mps_root_destroy(root_table);
@@ -192,6 +301,10 @@ static void *test(void *arg, size_t s)
 }
 
 
+/* main -- arena, thr, and tramp
+ *
+ * Then call main2.
+ */
 int main(int argc, char **argv)
 {
   mps_arena_t arena;
@@ -210,7 +323,7 @@ int main(int argc, char **argv)
   die(mps_thread_reg(&thr, arena), "thread");
   
   /* tramp: used for protection (barrier hits) */
-  trampFunction = test;
+  trampFunction = main2;
   trampData.arena = arena;
   trampData.thr = thr;
   mps_tramp(&trampResult, trampFunction, &trampData, sizeof trampData);