diff --git a/src/libCom/test/macDefExpandTest.c b/src/libCom/test/macDefExpandTest.c
new file mode 100644
index 000000000..bdbf41b3e
--- /dev/null
+++ b/src/libCom/test/macDefExpandTest.c
@@ -0,0 +1,147 @@
+/*************************************************************************\
+* Copyright (c) 2006 UChicago Argonne LLC, as Operator of Argonne
+*     National Laboratory.
+* Copyright (c) 2002 The Regents of the University of California, as
+*     Operator of Los Alamos National Laboratory.
+* EPICS BASE is distributed subject to a Software License Agreement found
+* in file LICENSE that is included with this distribution.
+\*************************************************************************/
+/*
+ * $Revision-Id$
+ */
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "macLib.h"
+#include "envDefs.h"
+#include "errlog.h"
+#include "epicsUnitTest.h"
+#include "testMain.h"
+
+static void check(const char *str, const char *macros, const char *expect)
+{
+    char *got = macDefExpand(str, macros);
+    int pass = -1;
+
+    if (expect && !got) {
+        testDiag("Got NULL, expected \"%s\".\n", expect);
+        pass = 0;
+    }
+    else if (!expect && got) {
+        testDiag("Got \"%s\", expected NULL.\n", got);
+        pass = 0;
+    }
+    else if (expect && got && strcmp(got, expect)) {
+        testDiag("Got \"%s\", expected \"%s\".\n", got, expect);
+        pass = 0;
+    }
+    testOk(pass, "%s", str);
+}
+
+MAIN(macEnvExpandTest)
+{
+    eltc(0);
+    testPlan(71);
+
+    check("FOO", NULL, "FOO");
+
+    check("${FOO}", NULL, NULL);
+    check("${FOO,BAR}", NULL, NULL);
+    check("${FOO,BAR=baz}", NULL, NULL);
+    check("${FOO,BAR=$(FOO)}", NULL, NULL);
+    check("${FOO,FOO}", NULL, NULL);
+    check("${FOO,FOO=$(FOO)}", NULL, NULL);
+    check("${FOO,BAR=baz,FUM}", NULL, NULL);
+
+    check("${=}", NULL, "");
+    check("x${=}y", NULL, "xy");
+
+    check("${,=}", NULL, "");
+    check("x${,=}y", NULL, "xy");
+
+    check("${FOO=}", NULL, "");
+    check("x${FOO=}y", NULL, "xy");
+
+    check("${FOO=,}", NULL, "");
+    check("x${FOO=,}y", NULL, "xy");
+
+    check("${FOO,FOO=}", NULL, "");
+    check("x${FOO,FOO=}y", NULL, "xy");
+
+    check("${FOO=,BAR}", NULL, "");
+    check("x${FOO=,BAR}y", NULL, "xy");
+
+    check("${FOO=$(BAR=)}", NULL, "");
+    check("x${FOO=$(BAR=)}y", NULL, "xy");
+
+    check("${FOO=,BAR=baz}", NULL, "");
+    check("x${FOO=,BAR=baz}y", NULL, "xy");
+
+    check("${FOO=$(BAR),BAR=}", NULL, "");
+    check("x${FOO=$(BAR),BAR=}y", NULL, "xy");
+
+    check("${=BAR}", NULL, "BAR");
+    check("x${=BAR}y", NULL, "xBARy");
+
+    check("${FOO=BAR}", NULL, "BAR");
+    check("x${FOO=BAR}y", NULL, "xBARy");
+
+    check("${FOO}", "FOO=BLETCH", "BLETCH");
+    check("${FOO,FOO}", "FOO=BLETCH", "BLETCH");
+    check("x${FOO}y", "FOO=BLETCH", "xBLETCHy");
+    check("x${FOO}y${FOO}z", "FOO=BLETCH", "xBLETCHyBLETCHz");
+    check("${FOO=BAR}", "FOO=BLETCH", "BLETCH");
+    check("x${FOO=BAR}y", "FOO=BLETCH", "xBLETCHy");
+    check("${FOO=${BAZ}}", "FOO=BLETCH", "BLETCH");
+    check("${FOO=${BAZ},BAR=$(BAZ)}", "FOO=BLETCH", "BLETCH");
+    check("x${FOO=${BAZ}}y", "FOO=BLETCH", "xBLETCHy");
+    check("x${FOO=${BAZ},BAR=$(BAZ)}y", "FOO=BLETCH", "xBLETCHy");
+    check("${BAR=${FOO}}", "FOO=BLETCH", "BLETCH");
+    check("x${BAR=${FOO}}y", "FOO=BLETCH", "xBLETCHy");
+    check("w${BAR=x${FOO}y}z", "FOO=BLETCH", "wxBLETCHyz");
+
+    check("${FOO,FOO=BAR}", "FOO=BLETCH", "BAR");
+    check("x${FOO,FOO=BAR}y", "FOO=BLETCH", "xBARy");
+    check("${BAR,BAR=$(FOO)}", "FOO=BLETCH", "BLETCH");
+    check("x${BAR,BAR=$(FOO)}y", "FOO=BLETCH", "xBLETCHy");
+    check("${BAR,BAR=$($(FOO)),BLETCH=GRIBBLE}", "FOO=BLETCH", "GRIBBLE");
+    check("x${BAR,BAR=$($(FOO)),BLETCH=GRIBBLE}y", "FOO=BLETCH", "xGRIBBLEy");
+    check("${$(BAR,BAR=$(FOO)),BLETCH=GRIBBLE}", "FOO=BLETCH", "GRIBBLE");
+    check("x${$(BAR,BAR=$(FOO)),BLETCH=GRIBBLE}y", "FOO=BLETCH", "xGRIBBLEy");
+
+    check("${FOO}/${BAR}", "BAR=GLEEP,FOO=BLETCH", "BLETCH/GLEEP");
+    check("x${FOO}/${BAR}y", "BAR=GLEEP,FOO=BLETCH", "xBLETCH/GLEEPy");
+    check("${FOO,BAR}/${BAR}", "BAR=GLEEP,FOO=BLETCH", "BLETCH/GLEEP");
+    check("${FOO,BAR=x}/${BAR}", "BAR=GLEEP,FOO=BLETCH", "BLETCH/GLEEP");
+    check("${BAZ=BLETCH,BAR}/${BAR}", "BAR=GLEEP,FOO=BLETCH", "BLETCH/GLEEP");
+    check("${BAZ=BLETCH,BAR=x}/${BAR}", "BAR=GLEEP,FOO=BLETCH", "BLETCH/GLEEP");
+    
+    check("${${FOO}}", "BAR=GLEEP,FOO=BLETCH,BLETCH=BAR", "BAR");
+    check("x${${FOO}}y", "BAR=GLEEP,FOO=BLETCH,BLETCH=BAR", "xBARy");
+    check("${${FOO}=GRIBBLE}", "BAR=GLEEP,FOO=BLETCH,BLETCH=BAR", "BAR");
+    check("x${${FOO}=GRIBBLE}y", "BAR=GLEEP,FOO=BLETCH,BLETCH=BAR", "xBARy");
+
+    check("${${FOO}}", "BAR=GLEEP,FOO=BLETCH,BLETCH=${BAR}", "GLEEP");
+
+    check("${FOO}", "BAR=GLEEP,FOO=${BAR},BLETCH=${BAR}" ,"GLEEP");
+
+    check("${FOO}", "BAR=${BAZ},FOO=${BAR},BLETCH=${BAR}", NULL);
+
+    check("${FOO}", "BAR=${BAZ=GRIBBLE},FOO=${BAR},BLETCH=${BAR}", "GRIBBLE");
+
+    check("${FOO}", "BAR=${STR1},FOO=${BAR},BLETCH=${BAR},STR1=VAL1,STR2=VAL2", "VAL1");
+
+    check("${FOO}", "BAR=${STR2},FOO=${BAR},BLETCH=${BAR},STR1=VAL1,STR2=VAL2", "VAL2");
+
+    check("${FOO}", "BAR=${FOO},FOO=${BAR},BLETCH=${BAR},STR1=VAL1,STR2=VAL2", NULL);
+    check("${FOO,FOO=$(FOO)}", "BAR=${FOO},FOO=${BAR},BLETCH=${BAR},STR1=VAL1,STR2=VAL2", NULL);
+    check("${FOO=$(FOO)}", "BAR=${FOO},FOO=${BAR},BLETCH=${BAR},STR1=VAL1,STR2=VAL2", NULL);
+    check("${FOO=$(BAR),BAR=$(FOO)}", "BAR=${FOO},FOO=${BAR},BLETCH=${BAR},STR1=VAL1,STR2=VAL2", NULL);
+    
+    errlogFlush();
+    eltc(1);
+    return testDone();
+}