diff --git a/src/testing/marry.c b/src/testing/marry.c
index 8cc944733..36b879c7b 100644
--- a/src/testing/marry.c
+++ b/src/testing/marry.c
@@ -92,6 +92,62 @@ nuts_scratch_addr(const char *scheme, size_t sz, char *addr)
 	abort();
 }
 
+void
+nuts_scratch_addr_zero(const char *scheme, size_t sz, char *addr)
+{
+	if ((strcmp(scheme, "inproc") == 0) ||
+	    (strcmp(scheme, "abstract") == 0)) {
+		(void) snprintf(addr, sz, "%s://nuts%04x%04x%04x%04x", scheme,
+		    nng_random(), nng_random(), nng_random(), nng_random());
+		return;
+	}
+
+	if ((strncmp(scheme, "tcp", 3) == 0) ||
+	    (strncmp(scheme, "tls", 3) == 0) ||
+	    (strncmp(scheme, "udp", 3) == 0)) {
+		const char *ip =
+		    strchr(scheme, '6') != NULL ? "[::1]" : "127.0.0.1";
+		(void) snprintf(addr, sz, "%s://%s:%u", scheme, ip, 0);
+		return;
+	}
+
+	if (strncmp(scheme, "ws", 2) == 0) {
+		const char *ip =
+		    strchr(scheme, '6') != NULL ? "[::1]" : "127.0.0.1";
+		(void) snprintf(addr, sz, "%s://%s:%u/nuts%04x%04x%04x%04x",
+		    scheme, ip, 0, nng_random(), nng_random(), nng_random(),
+		    nng_random());
+		return;
+	}
+
+	if ((strncmp(scheme, "ipc", 3) == 0) ||
+	    (strncmp(scheme, "unix", 4) == 0)) {
+#ifdef _WIN32
+		// Windows doesn't place IPC names in the filesystem.
+		(void) snprintf(addr, sz, "%s://nuts%04x%04x%04x%04x", scheme,
+		    nng_random(), nng_random(), nng_random(), nng_random());
+		return;
+#else
+		char *tmpdir;
+
+		if (((tmpdir = getenv("TMPDIR")) == NULL) &&
+		    ((tmpdir = getenv("TEMP")) == NULL) &&
+		    ((tmpdir = getenv("TMP")) == NULL)) {
+			tmpdir = "/tmp";
+		}
+
+		(void) snprintf(addr, sz, "%s://%s/nuts%04x%04x%04x%04x",
+		    scheme, tmpdir, nng_random(), nng_random(), nng_random(),
+		    nng_random());
+		return;
+#endif
+	}
+
+	// We should not be here.
+	nng_log_err("NUTS", "Unknown scheme");
+	abort();
+}
+
 // nuts_next_port returns a "next" allocation port.
 // Ports are chosen by starting from a random point within a
 // range (normally 38000-40000, but other good places to choose
diff --git a/src/testing/nuts.h b/src/testing/nuts.h
index 5fe193db1..f2e50c2c8 100644
--- a/src/testing/nuts.h
+++ b/src/testing/nuts.h
@@ -85,6 +85,10 @@ extern uint16_t nuts_next_port(void);
 // 64 bytes to ensure no truncation occurs.
 extern void nuts_scratch_addr(const char *, size_t, char *);
 
+// like nuts_scratch_addr, but attempts to use an autobind (0 port)
+// address instead.
+extern void nuts_scratch_addr_zero(const char *, size_t, char *);
+
 // nuts_marry connects two sockets using inproc.  It uses socket
 // pipe hooks to ensure that it does not return before both sockets
 // are fully connected.
@@ -264,6 +268,14 @@ extern const char *nuts_ecdsa_client_crt;
 		(var) = nuts_addr_;                                        \
 	} while (0)
 
+#define NUTS_ADDR_ZERO(var, scheme)                          \
+	do {                                                 \
+		static char nuts_addr_[64];                  \
+		nuts_scratch_addr_zero(                      \
+		    scheme, sizeof(nuts_addr_), nuts_addr_); \
+		(var) = nuts_addr_;                          \
+	} while (0)
+
 #define NUTS_OPEN(sock) NUTS_PASS(nng_pair1_open(&(sock)))
 
 #define NUTS_CLOSE(sock) NUTS_PASS(nng_close(sock))
diff --git a/src/testing/util.c b/src/testing/util.c
index d569bf5f4..2bb882b7a 100644
--- a/src/testing/util.c
+++ b/src/testing/util.c
@@ -286,16 +286,18 @@ nuts_tran_dialer_closed(const char *scheme)
 void
 nuts_tran_duplicate_listen(const char *scheme)
 {
-	nng_socket   s  = NNG_SOCKET_INITIALIZER;
-	nng_listener l1 = NNG_LISTENER_INITIALIZER;
-	nng_listener l2 = NNG_LISTENER_INITIALIZER;
-	const char  *addr;
+	nng_socket     s  = NNG_SOCKET_INITIALIZER;
+	nng_listener   l1 = NNG_LISTENER_INITIALIZER;
+	nng_listener   l2 = NNG_LISTENER_INITIALIZER;
+	const char    *addr;
+	const nng_url *url;
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
-	NUTS_ADDR(addr, scheme);
+	NUTS_ADDR_ZERO(addr, scheme);
 	NUTS_OPEN(s);
 	NUTS_PASS(nng_listen(s, addr, &l1, 0));
-	NUTS_FAIL(nng_listen(s, addr, &l2, 0), NNG_EADDRINUSE);
+	NUTS_PASS(nng_listener_get_url(l1, &url));
+	NUTS_FAIL(nng_listen_url(s, url, &l2, 0), NNG_EADDRINUSE);
 	NUTS_TRUE(nng_listener_id(l1) > 0);
 	NUTS_TRUE(nng_listener_id(l2) < 0);
 	NUTS_CLOSE(s);
@@ -309,7 +311,7 @@ nuts_tran_listener_cancel(const char *scheme)
 	const char  *addr;
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
-	NUTS_ADDR(addr, scheme);
+	NUTS_ADDR_ZERO(addr, scheme);
 	NUTS_OPEN(s);
 	NUTS_PASS(nng_listen(s, addr, &l, 0));
 	NUTS_TRUE(nng_listener_id(l) > 0);
@@ -325,7 +327,7 @@ nuts_tran_listener_closed(const char *scheme)
 	const char  *addr;
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
-	NUTS_ADDR(addr, scheme);
+	NUTS_ADDR_ZERO(addr, scheme);
 	NUTS_OPEN(s);
 	NUTS_PASS(nng_listener_create(&l, s, addr));
 	NUTS_TRUE(nng_listener_id(l) > 0);
@@ -337,15 +339,16 @@ nuts_tran_listener_closed(const char *scheme)
 void
 nuts_tran_listen_accept(const char *scheme)
 {
-	nng_socket   s1 = NNG_SOCKET_INITIALIZER;
-	nng_socket   s2 = NNG_SOCKET_INITIALIZER;
-	nng_listener l1 = NNG_LISTENER_INITIALIZER;
-	nng_dialer   d1 = NNG_LISTENER_INITIALIZER;
-	nng_dialer   d2 = NNG_LISTENER_INITIALIZER;
-	const char  *addr;
+	nng_socket     s1 = NNG_SOCKET_INITIALIZER;
+	nng_socket     s2 = NNG_SOCKET_INITIALIZER;
+	nng_listener   l1 = NNG_LISTENER_INITIALIZER;
+	nng_dialer     d1 = NNG_LISTENER_INITIALIZER;
+	nng_dialer     d2 = NNG_LISTENER_INITIALIZER;
+	const char    *addr;
+	const nng_url *url;
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
-	NUTS_ADDR(addr, scheme);
+	NUTS_ADDR_ZERO(addr, scheme);
 	NUTS_OPEN(s1);
 	NUTS_OPEN(s2);
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_SENDTIMEO, 100));
@@ -353,8 +356,9 @@ nuts_tran_listen_accept(const char *scheme)
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_socket_set_ms(s2, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_listen(s1, addr, &l1, 0));
-	NUTS_PASS(nng_dial(s2, addr, &d1, 0));
-	NUTS_PASS(nng_dial(s2, addr, &d2, 0));
+	NUTS_PASS(nng_listener_get_url(l1, &url));
+	NUTS_PASS(nng_dial_url(s2, url, &d1, 0));
+	NUTS_PASS(nng_dial_url(s2, url, &d2, 0));
 	NUTS_TRUE(nng_listener_id(l1) > 0);
 	NUTS_TRUE(nng_dialer_id(d1) > 0);
 	NUTS_TRUE(nng_dialer_id(d2) > 0);
@@ -366,14 +370,15 @@ nuts_tran_listen_accept(const char *scheme)
 void
 nuts_tran_exchange(const char *scheme)
 {
-	nng_socket   s1 = NNG_SOCKET_INITIALIZER;
-	nng_socket   s2 = NNG_SOCKET_INITIALIZER;
-	nng_listener l1 = NNG_LISTENER_INITIALIZER;
-	nng_dialer   d1 = NNG_LISTENER_INITIALIZER;
-	const char  *addr;
+	nng_socket     s1 = NNG_SOCKET_INITIALIZER;
+	nng_socket     s2 = NNG_SOCKET_INITIALIZER;
+	nng_listener   l1 = NNG_LISTENER_INITIALIZER;
+	nng_dialer     d1 = NNG_LISTENER_INITIALIZER;
+	const char    *addr;
+	const nng_url *url;
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
-	NUTS_ADDR(addr, scheme);
+	NUTS_ADDR_ZERO(addr, scheme);
 	NUTS_OPEN(s1);
 	NUTS_OPEN(s2);
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_SENDTIMEO, 100));
@@ -381,7 +386,8 @@ nuts_tran_exchange(const char *scheme)
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_socket_set_ms(s2, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_listen(s1, addr, &l1, 0));
-	NUTS_PASS(nng_dial(s2, addr, &d1, 0));
+	NUTS_PASS(nng_listener_get_url(l1, &url));
+	NUTS_PASS(nng_dial_url(s2, url, &d1, 0));
 	NUTS_TRUE(nng_listener_id(l1) > 0);
 	NUTS_TRUE(nng_dialer_id(d1) > 0);
 	for (int i = 0; i < 5; i++) {
@@ -397,17 +403,18 @@ nuts_tran_exchange(const char *scheme)
 void
 nuts_tran_pipe_id(const char *scheme)
 {
-	nng_socket   s1 = NNG_SOCKET_INITIALIZER;
-	nng_socket   s2 = NNG_SOCKET_INITIALIZER;
-	nng_listener l1 = NNG_LISTENER_INITIALIZER;
-	nng_dialer   d1 = NNG_LISTENER_INITIALIZER;
-	const char  *addr;
-	nng_msg     *msg;
-	nng_pipe     p1;
-	nng_pipe     p2;
+	nng_socket     s1 = NNG_SOCKET_INITIALIZER;
+	nng_socket     s2 = NNG_SOCKET_INITIALIZER;
+	nng_listener   l1 = NNG_LISTENER_INITIALIZER;
+	nng_dialer     d1 = NNG_LISTENER_INITIALIZER;
+	const char    *addr;
+	nng_msg       *msg;
+	nng_pipe       p1;
+	nng_pipe       p2;
+	const nng_url *url;
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
-	NUTS_ADDR(addr, scheme);
+	NUTS_ADDR_ZERO(addr, scheme);
 	NUTS_OPEN(s1);
 	NUTS_OPEN(s2);
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_SENDTIMEO, 100));
@@ -415,7 +422,8 @@ nuts_tran_pipe_id(const char *scheme)
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_socket_set_ms(s2, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_listen(s1, addr, &l1, 0));
-	NUTS_PASS(nng_dial(s2, addr, &d1, 0));
+	NUTS_PASS(nng_listener_get_url(l1, &url));
+	NUTS_PASS(nng_dial_url(s2, url, &d1, 0));
 	NUTS_TRUE(nng_listener_id(l1) > 0);
 	NUTS_TRUE(nng_dialer_id(d1) > 0);
 	NUTS_SEND(s1, "ping");
@@ -438,18 +446,19 @@ nuts_tran_pipe_id(const char *scheme)
 void
 nuts_tran_huge_msg(const char *scheme, size_t size)
 {
-	nng_socket   s1 = NNG_SOCKET_INITIALIZER;
-	nng_socket   s2 = NNG_SOCKET_INITIALIZER;
-	nng_listener l1 = NNG_LISTENER_INITIALIZER;
-	nng_dialer   d1 = NNG_LISTENER_INITIALIZER;
-	const char  *addr;
-	char        *buf;
-	nng_msg     *msg;
+	nng_socket     s1 = NNG_SOCKET_INITIALIZER;
+	nng_socket     s2 = NNG_SOCKET_INITIALIZER;
+	nng_listener   l1 = NNG_LISTENER_INITIALIZER;
+	nng_dialer     d1 = NNG_LISTENER_INITIALIZER;
+	const char    *addr;
+	char          *buf;
+	nng_msg       *msg;
+	const nng_url *url;
 
 	buf = nng_alloc(size);
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
-	NUTS_ADDR(addr, scheme);
+	NUTS_ADDR_ZERO(addr, scheme);
 	NUTS_OPEN(s1);
 	NUTS_OPEN(s2);
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_SENDTIMEO, 5000));
@@ -457,7 +466,8 @@ nuts_tran_huge_msg(const char *scheme, size_t size)
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_RECVTIMEO, 5000));
 	NUTS_PASS(nng_socket_set_ms(s2, NNG_OPT_RECVTIMEO, 5000));
 	NUTS_PASS(nng_listen(s1, addr, &l1, 0));
-	NUTS_PASS(nng_dial(s2, addr, &d1, 0));
+	NUTS_PASS(nng_listener_get_url(l1, &url));
+	NUTS_PASS(nng_dial_url(s2, url, &d1, 0));
 	NUTS_TRUE(nng_listener_id(l1) > 0);
 	NUTS_TRUE(nng_dialer_id(d1) > 0);
 	for (int i = 0; i < 5; i++) {
@@ -483,12 +493,13 @@ nuts_tran_huge_msg(const char *scheme, size_t size)
 void
 nuts_tran_msg_props(const char *scheme, void (*check)(nng_msg *))
 {
-	nng_socket   s1 = NNG_SOCKET_INITIALIZER;
-	nng_socket   s2 = NNG_SOCKET_INITIALIZER;
-	nng_listener l1 = NNG_LISTENER_INITIALIZER;
-	nng_dialer   d1 = NNG_LISTENER_INITIALIZER;
-	const char  *addr;
-	nng_msg     *msg;
+	nng_socket     s1 = NNG_SOCKET_INITIALIZER;
+	nng_socket     s2 = NNG_SOCKET_INITIALIZER;
+	nng_listener   l1 = NNG_LISTENER_INITIALIZER;
+	nng_dialer     d1 = NNG_LISTENER_INITIALIZER;
+	const char    *addr;
+	nng_msg       *msg;
+	const nng_url *url;
 
 	NUTS_SKIP_IF_IPV6_NEEDED_AND_ABSENT(scheme);
 	NUTS_ADDR(addr, scheme);
@@ -499,7 +510,8 @@ nuts_tran_msg_props(const char *scheme, void (*check)(nng_msg *))
 	NUTS_PASS(nng_socket_set_ms(s1, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_socket_set_ms(s2, NNG_OPT_RECVTIMEO, 100));
 	NUTS_PASS(nng_listen(s1, addr, &l1, 0));
-	NUTS_PASS(nng_dial(s2, addr, &d1, 0));
+	NUTS_PASS(nng_listener_get_url(l1, &url));
+	NUTS_PASS(nng_dial_url(s2, url, &d1, 0));
 	NUTS_TRUE(nng_listener_id(l1) > 0);
 	NUTS_TRUE(nng_dialer_id(d1) > 0);
 	NUTS_SEND(s1, "ping");