diff --git a/tools/testing/vsock/Makefile b/tools/testing/vsock/Makefile
index 66ba0924194d..cf0650007fa8 100644
--- a/tools/testing/vsock/Makefile
+++ b/tools/testing/vsock/Makefile
@@ -1,6 +1,6 @@
 all: test
 test: vsock_diag_test
-vsock_diag_test: vsock_diag_test.o timeout.o control.o
+vsock_diag_test: vsock_diag_test.o timeout.o control.o util.o
 
 CFLAGS += -g -O2 -Werror -Wall -I. -I../../include/uapi -I../../include -Wno-pointer-sign -fno-strict-overflow -fno-strict-aliasing -fno-common -MMD -U_FORTIFY_SOURCE -D_GNU_SOURCE
 .PHONY: all test clean
diff --git a/tools/testing/vsock/util.h b/tools/testing/vsock/util.h
new file mode 100644
index 000000000000..a51e17578ccf
--- /dev/null
+++ b/tools/testing/vsock/util.h
@@ -0,0 +1,35 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+/* Tests can either run as the client or the server */
+enum test_mode {
+	TEST_MODE_UNSET,
+	TEST_MODE_CLIENT,
+	TEST_MODE_SERVER
+};
+
+/* Test runner options */
+struct test_opts {
+	enum test_mode mode;
+	unsigned int peer_cid;
+};
+
+/* A test case definition.  Test functions must print failures to stderr and
+ * terminate with exit(EXIT_FAILURE).
+ */
+struct test_case {
+	const char *name; /* human-readable name */
+
+	/* Called when test mode is TEST_MODE_CLIENT */
+	void (*run_client)(const struct test_opts *opts);
+
+	/* Called when test mode is TEST_MODE_SERVER */
+	void (*run_server)(const struct test_opts *opts);
+};
+
+void init_signals(void);
+unsigned int parse_cid(const char *str);
+void run_tests(const struct test_case *test_cases,
+	       const struct test_opts *opts);
+
+#endif /* UTIL_H */
diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
new file mode 100644
index 000000000000..2567abd90153
--- /dev/null
+++ b/tools/testing/vsock/util.c
@@ -0,0 +1,70 @@
+/*
+ * vsock test utilities
+ *
+ * Copyright (C) 2017 Red Hat, Inc.
+ *
+ * Author: Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+
+#include "timeout.h"
+#include "util.h"
+
+/* Install signal handlers */
+void init_signals(void)
+{
+	struct sigaction act = {
+		.sa_handler = sigalrm,
+	};
+
+	sigaction(SIGALRM, &act, NULL);
+	signal(SIGPIPE, SIG_IGN);
+}
+
+/* Parse a CID in string representation */
+unsigned int parse_cid(const char *str)
+{
+	char *endptr = NULL;
+	unsigned long int n;
+
+	errno = 0;
+	n = strtoul(str, &endptr, 10);
+	if (errno || *endptr != '\0') {
+		fprintf(stderr, "malformed CID \"%s\"\n", str);
+		exit(EXIT_FAILURE);
+	}
+	return n;
+}
+
+/* Run test cases.  The program terminates if a failure occurs. */
+void run_tests(const struct test_case *test_cases,
+	       const struct test_opts *opts)
+{
+	int i;
+
+	for (i = 0; test_cases[i].name; i++) {
+		void (*run)(const struct test_opts *opts);
+
+		printf("%s...", test_cases[i].name);
+		fflush(stdout);
+
+		if (opts->mode == TEST_MODE_CLIENT)
+			run = test_cases[i].run_client;
+		else
+			run = test_cases[i].run_server;
+
+		if (run)
+			run(opts);
+
+		printf("ok\n");
+	}
+}
diff --git a/tools/testing/vsock/vsock_diag_test.c b/tools/testing/vsock/vsock_diag_test.c
index e896a4af52f4..f1ace5d96e00 100644
--- a/tools/testing/vsock/vsock_diag_test.c
+++ b/tools/testing/vsock/vsock_diag_test.c
@@ -13,12 +13,10 @@
 
 #include <getopt.h>
 #include <stdio.h>
-#include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include <unistd.h>
-#include <signal.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -33,12 +31,7 @@
 
 #include "timeout.h"
 #include "control.h"
-
-enum test_mode {
-	TEST_MODE_UNSET,
-	TEST_MODE_CLIENT,
-	TEST_MODE_SERVER
-};
+#include "util.h"
 
 /* Per-socket status */
 struct vsock_stat {
@@ -339,7 +332,7 @@ static void free_sock_stat(struct list_head *sockets)
 		free(st);
 }
 
-static void test_no_sockets(unsigned int peer_cid)
+static void test_no_sockets(const struct test_opts *opts)
 {
 	LIST_HEAD(sockets);
 
@@ -350,7 +343,7 @@ static void test_no_sockets(unsigned int peer_cid)
 	free_sock_stat(&sockets);
 }
 
-static void test_listen_socket_server(unsigned int peer_cid)
+static void test_listen_socket_server(const struct test_opts *opts)
 {
 	union {
 		struct sockaddr sa;
@@ -388,7 +381,7 @@ static void test_listen_socket_server(unsigned int peer_cid)
 	free_sock_stat(&sockets);
 }
 
-static void test_connect_client(unsigned int peer_cid)
+static void test_connect_client(const struct test_opts *opts)
 {
 	union {
 		struct sockaddr sa;
@@ -397,7 +390,7 @@ static void test_connect_client(unsigned int peer_cid)
 		.svm = {
 			.svm_family = AF_VSOCK,
 			.svm_port = 1234,
-			.svm_cid = peer_cid,
+			.svm_cid = opts->peer_cid,
 		},
 	};
 	int fd;
@@ -434,7 +427,7 @@ static void test_connect_client(unsigned int peer_cid)
 	free_sock_stat(&sockets);
 }
 
-static void test_connect_server(unsigned int peer_cid)
+static void test_connect_server(const struct test_opts *opts)
 {
 	union {
 		struct sockaddr sa;
@@ -486,9 +479,9 @@ static void test_connect_server(unsigned int peer_cid)
 			clientaddr.sa.sa_family);
 		exit(EXIT_FAILURE);
 	}
-	if (clientaddr.svm.svm_cid != peer_cid) {
+	if (clientaddr.svm.svm_cid != opts->peer_cid) {
 		fprintf(stderr, "expected peer CID %u from accept(2), got %u\n",
-			peer_cid, clientaddr.svm.svm_cid);
+			opts->peer_cid, clientaddr.svm.svm_cid);
 		exit(EXIT_FAILURE);
 	}
 
@@ -507,11 +500,7 @@ static void test_connect_server(unsigned int peer_cid)
 	free_sock_stat(&sockets);
 }
 
-static struct {
-	const char *name;
-	void (*run_client)(unsigned int peer_cid);
-	void (*run_server)(unsigned int peer_cid);
-} test_cases[] = {
+static struct test_case test_cases[] = {
 	{
 		.name = "No sockets",
 		.run_server = test_no_sockets,
@@ -528,30 +517,6 @@ static struct {
 	{},
 };
 
-static void init_signals(void)
-{
-	struct sigaction act = {
-		.sa_handler = sigalrm,
-	};
-
-	sigaction(SIGALRM, &act, NULL);
-	signal(SIGPIPE, SIG_IGN);
-}
-
-static unsigned int parse_cid(const char *str)
-{
-	char *endptr = NULL;
-	unsigned long int n;
-
-	errno = 0;
-	n = strtoul(str, &endptr, 10);
-	if (errno || *endptr != '\0') {
-		fprintf(stderr, "malformed CID \"%s\"\n", str);
-		exit(EXIT_FAILURE);
-	}
-	return n;
-}
-
 static const char optstring[] = "";
 static const struct option longopts[] = {
 	{
@@ -606,9 +571,10 @@ int main(int argc, char **argv)
 {
 	const char *control_host = NULL;
 	const char *control_port = NULL;
-	int mode = TEST_MODE_UNSET;
-	unsigned int peer_cid = VMADDR_CID_ANY;
-	int i;
+	struct test_opts opts = {
+		.mode = TEST_MODE_UNSET,
+		.peer_cid = VMADDR_CID_ANY,
+	};
 
 	init_signals();
 
@@ -624,16 +590,16 @@ int main(int argc, char **argv)
 			break;
 		case 'm':
 			if (strcmp(optarg, "client") == 0)
-				mode = TEST_MODE_CLIENT;
+				opts.mode = TEST_MODE_CLIENT;
 			else if (strcmp(optarg, "server") == 0)
-				mode = TEST_MODE_SERVER;
+				opts.mode = TEST_MODE_SERVER;
 			else {
 				fprintf(stderr, "--mode must be \"client\" or \"server\"\n");
 				return EXIT_FAILURE;
 			}
 			break;
 		case 'p':
-			peer_cid = parse_cid(optarg);
+			opts.peer_cid = parse_cid(optarg);
 			break;
 		case 'P':
 			control_port = optarg;
@@ -646,35 +612,21 @@ int main(int argc, char **argv)
 
 	if (!control_port)
 		usage();
-	if (mode == TEST_MODE_UNSET)
+	if (opts.mode == TEST_MODE_UNSET)
 		usage();
-	if (peer_cid == VMADDR_CID_ANY)
+	if (opts.peer_cid == VMADDR_CID_ANY)
 		usage();
 
 	if (!control_host) {
-		if (mode != TEST_MODE_SERVER)
+		if (opts.mode != TEST_MODE_SERVER)
 			usage();
 		control_host = "0.0.0.0";
 	}
 
-	control_init(control_host, control_port, mode == TEST_MODE_SERVER);
+	control_init(control_host, control_port,
+		     opts.mode == TEST_MODE_SERVER);
 
-	for (i = 0; test_cases[i].name; i++) {
-		void (*run)(unsigned int peer_cid);
-
-		printf("%s...", test_cases[i].name);
-		fflush(stdout);
-
-		if (mode == TEST_MODE_CLIENT)
-			run = test_cases[i].run_client;
-		else
-			run = test_cases[i].run_server;
-
-		if (run)
-			run(peer_cid);
-
-		printf("ok\n");
-	}
+	run_tests(test_cases, &opts);
 
 	control_cleanup();
 	return EXIT_SUCCESS;
