diff --git a/test/test-ctl-fuzz.c b/test/test-ctl-fuzz.c
index 501fd6c..3382e32 100644
--- a/test/test-ctl-fuzz.c
+++ b/test/test-ctl-fuzz.c
@@ -1,10 +1,10 @@
-#include <assert.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 
 #include "init.h"
+#include "test-util.h"
 #include "util.h"
 #include "wepoll.h"
 #include "win.h"
@@ -22,16 +22,16 @@ static SOCKET create_and_add_socket(HANDLE epfd) {
   struct epoll_event ev;
 
   sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
-  assert(sock > 0);
+  check(sock > 0);
 
   one = 1;
   r = ioctlsocket(sock, FIONBIO, &one);
-  assert(r == 0);
+  check(r == 0);
 
   ev.events = 0;
   ev.data.u64 = 42;
   r = epoll_ctl(epfd, EPOLL_CTL_ADD, sock, &ev);
-  assert(r == 0);
+  check(r == 0);
 
   return sock;
 }
@@ -44,10 +44,10 @@ int main(void) {
   HANDLE epfd;
 
   r = init();
-  assert(r == 0);
+  check(r == 0);
 
   epfd = epoll_create1(0);
-  assert(epfd != NULL);
+  check(epfd != NULL);
 
   for (size_t i = 0; i < NUM_SOCKETS; i++)
     sockets[i] = create_and_add_socket(epfd);
@@ -67,13 +67,13 @@ int main(void) {
       ev_in.data.u64 = 42;
 
       r = epoll_ctl(epfd, EPOLL_CTL_MOD, sock, &ev_in);
-      assert(r == 0);
+      check(r == 0);
     }
 
     count = 0;
     do {
       r = epoll_wait(epfd, ev_out, array_count(ev_out), count > 0 ? 0 : -1);
-      assert(r >= 0);
+      check(r >= 0);
       count += r;
     } while (r > 0);
 
diff --git a/test/test-multi-poll.c b/test/test-multi-poll.c
index 9f300fd..87e7890 100644
--- a/test/test-multi-poll.c
+++ b/test/test-multi-poll.c
@@ -1,10 +1,10 @@
-#include <assert.h>
 #include <process.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 
 #include "init.h"
+#include "test-util.h"
 #include "util.h"
 #include "wepoll.h"
 #include "win.h"
@@ -30,17 +30,17 @@ static SOCKET create_socket(unsigned short port) {
   int r;
 
   sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
-  assert(sock > 0);
+  check(sock > 0);
 
   address.sin_family = AF_INET;
   address.sin_port = htons(port);
   address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
   r = bind(sock, (struct sockaddr*) &address, sizeof address);
-  assert(r == 0);
+  check(r == 0);
 
   one = 1;
   r = ioctlsocket(sock, FIONBIO, &one);
-  assert(r == 0);
+  check(r == 0);
 
   return sock;
 }
@@ -68,7 +68,7 @@ static void send_message(SOCKET sock, unsigned short port) {
                 sizeof address,
                 NULL,
                 NULL);
-  assert(r >= 0);
+  check(r >= 0);
 }
 
 static unsigned int __stdcall poll_thread(void* arg) {
@@ -78,10 +78,10 @@ static unsigned int __stdcall poll_thread(void* arg) {
 
   memset(&ev_out, 0, sizeof ev_out);
   r = epoll_wait(context->port, &ev_out, 1, -1);
-  assert(r == 1);
+  check(r == 1);
 
-  assert(ev_out.events == EPOLLIN);
-  assert(ev_out.data.u64 == context->data);
+  check(ev_out.events == EPOLLIN);
+  check(ev_out.data.u64 == context->data);
 
   printf("Got event (port %p, thread %p)\n", context->port, context->thread);
 
@@ -96,7 +96,7 @@ int main(void) {
 
   /* Initialize winsock. */
   r = WSAStartup(MAKEWORD(2, 2), &wsa_data);
-  assert(r == 0);
+  check(r == 0);
 
   SOCKET send_sock = create_socket(0);
   SOCKET recv_sock = create_socket(LISTEN_PORT);
@@ -109,14 +109,14 @@ int main(void) {
 
     /* Create epoll port. */
     port = epoll_create1(0);
-    assert(port != INVALID_HANDLE_VALUE);
+    check(port != INVALID_HANDLE_VALUE);
     ports[i] = port;
 
     /* Register recv_sock with the epoll port. */
     ev.events = EPOLLIN;
     ev.data.u64 = rand();
     r = epoll_ctl(port, EPOLL_CTL_ADD, recv_sock, &ev);
-    assert(r == 0);
+    check(r == 0);
 
     /* Start THREADS_PER_PORT threads which will all poll the port. */
     for (size_t j = 0; j < array_count(contexts[i]); j++) {
@@ -131,7 +131,7 @@ int main(void) {
       /* Start thread. */
       thread = (HANDLE) _beginthreadex(
           NULL, 0, poll_thread, (void*) context, 0, NULL);
-      assert(thread != INVALID_HANDLE_VALUE);
+      check(thread != INVALID_HANDLE_VALUE);
       context->thread = thread;
     }
   }
@@ -147,7 +147,7 @@ int main(void) {
     for (size_t j = 0; j < array_count(contexts[i]); j++) {
       HANDLE thread = contexts[i][j].thread;
       DWORD wr = WaitForSingleObject(thread, INFINITE);
-      assert(wr == WAIT_OBJECT_0);
+      check(wr == WAIT_OBJECT_0);
       CloseHandle(thread);
     }
   }
@@ -156,7 +156,7 @@ int main(void) {
   for (size_t i = 0; i < array_count(ports); i++) {
     HANDLE port = ports[i];
     r = epoll_close(port);
-    assert(r == 0);
+    check(r == 0);
   }
 
   return 0;
diff --git a/test/test-oneshot-and-hangup.c b/test/test-oneshot-and-hangup.c
index 02c5caf..b93d245 100644
--- a/test/test-oneshot-and-hangup.c
+++ b/test/test-oneshot-and-hangup.c
@@ -1,8 +1,8 @@
-#include <assert.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>
 
+#include "test-util.h"
 #include "wepoll.h"
 #include "win.h"
 
@@ -67,14 +67,14 @@ int main(void) {
   {
     /* Create an epoll instance. */
     epoll_port = epoll_create(1);
-    assert(epoll_port > 0);
+    check(epoll_port > 0);
   }
 
   {
     /* Create a TCP socket pair. */
     SOCKET socks[2];
     int r = tcp_socketpair(socks);
-    assert(r == 0);
+    check(r == 0);
 
     send_sock = socks[0];
     recv_sock = socks[1];
@@ -83,13 +83,13 @@ int main(void) {
   {
     /* Enable non-blocking mode on the receiving end. */
     int r = sock_set_nonblock(recv_sock, true);
-    assert(r == 0);
+    check(r == 0);
   }
 
   {
     /* Send some data in order to trigger an event on the receiving socket. */
     int r = send(send_sock, HELLO, sizeof HELLO, 0);
-    assert(r == sizeof HELLO);
+    check(r == sizeof HELLO);
   }
 
   {
@@ -101,7 +101,7 @@ int main(void) {
     ev.data.sock = recv_sock;
 
     r = epoll_ctl(epoll_port, EPOLL_CTL_ADD, recv_sock, &ev);
-    assert(r >= 0);
+    check(r >= 0);
   }
 
   {
@@ -112,16 +112,16 @@ int main(void) {
     memset(&ev, 0, sizeof ev);
 
     r = epoll_wait(epoll_port, &ev, 1, -1);
-    assert(r == 1);
-    assert(ev.events == EPOLLIN);
-    assert(ev.data.sock == recv_sock);
+    check(r == 1);
+    check(ev.events == EPOLLIN);
+    check(ev.data.sock == recv_sock);
   }
 
   {
     /* Read the data from the socket. */
     char buffer[16];
     int r = recv(recv_sock, buffer, sizeof buffer, 0);
-    assert(r > 0);
+    check(r > 0);
   }
 
   {
@@ -134,7 +134,7 @@ int main(void) {
     memset(&ev, 0, sizeof ev);
 
     r = epoll_wait(epoll_port, &ev, 1, timeout);
-    assert(r == 0); /* Time-out. */
+    check(r == 0); /* Time-out. */
   }
 
   {
@@ -149,9 +149,9 @@ int main(void) {
 
     r = epoll_ctl(epoll_port, EPOLL_CTL_ADD, recv_sock, &ev);
 
-    assert(r == -1);
-    assert(errno == EEXIST);
-    assert(GetLastError() == ERROR_ALREADY_EXISTS);
+    check(r == -1);
+    check(errno == EEXIST);
+    check(GetLastError() == ERROR_ALREADY_EXISTS);
   }
 
   {
@@ -163,20 +163,20 @@ int main(void) {
     ev.data.sock = recv_sock;
 
     r = epoll_ctl(epoll_port, EPOLL_CTL_MOD, recv_sock, &ev);
-    assert(r == 0);
+    check(r == 0);
   }
 
   {
     /* Send some data, which will never be read by the receiving end, otherwise
      * Windows won't detect that the connection is closed. */
     int r = send(send_sock, HELLO, sizeof HELLO, 0);
-    assert(r == sizeof HELLO);
+    check(r == sizeof HELLO);
   }
 
   {
     /* Send FIN packet. */
     int r = shutdown(send_sock, SD_SEND);
-    assert(r == 0);
+    check(r == 0);
   }
 
   {
@@ -187,16 +187,16 @@ int main(void) {
     memset(&ev, 0, sizeof ev);
 
     r = epoll_wait(epoll_port, &ev, 1, -1);
-    assert(r == 1);
-    assert(ev.events == EPOLLRDHUP);
-    assert(ev.data.sock == recv_sock);
+    check(r == 1);
+    check(ev.events == EPOLLRDHUP);
+    check(ev.data.sock == recv_sock);
   }
 
   {
     /* Close to receiving socket, so the sending socket should detect a
      * connection hang-up */
     int r = closesocket(recv_sock);
-    assert(r == 0);
+    check(r == 0);
   }
 
   {
@@ -211,7 +211,7 @@ int main(void) {
     ev.data.sock = send_sock;
 
     r = epoll_ctl(epoll_port, EPOLL_CTL_ADD, send_sock, &ev);
-    assert(r == 0);
+    check(r == 0);
   }
 
   {
@@ -222,21 +222,21 @@ int main(void) {
     memset(&ev, 0, sizeof ev);
 
     r = epoll_wait(epoll_port, &ev, 1, -1);
-    assert(r == 1);
-    assert(ev.events == EPOLLHUP);
-    assert(ev.data.sock == send_sock);
+    check(r == 1);
+    check(ev.events == EPOLLHUP);
+    check(ev.data.sock == send_sock);
   }
 
   {
     /* Close the send socket. */
     int r = closesocket(send_sock);
-    assert(r == 0);
+    check(r == 0);
   }
 
   {
     /* Close the epoll port. */
     int r = epoll_close(epoll_port);
-    assert(r == 0);
+    check(r == 0);
   }
 
   return 0;
diff --git a/test/test-reflock.c b/test/test-reflock.c
index 656efeb..3526f58 100644
--- a/test/test-reflock.c
+++ b/test/test-reflock.c
@@ -1,4 +1,3 @@
-#include <assert.h>
 #include <process.h>
 #include <stdbool.h>
 #include <stdio.h>
@@ -6,6 +5,7 @@
 
 #include "init.h"
 #include "reflock.h"
+#include "test-util.h"
 #include "util.h"
 #include "win.h"
 
@@ -53,7 +53,7 @@ static unsigned int __stdcall test_thread(void* arg) {
 
   ReleaseSRWLockShared(&context->srwlock);
 
-  assert(lock_count > 100); /* Hopefully much more. */
+  check(lock_count > 100); /* Hopefully much more. */
 
   return 0;
 }
@@ -76,7 +76,7 @@ static void run_test_iteration(void) {
   for (size_t i = 0; i < array_count(threads); i++) {
     HANDLE thread =
         (HANDLE) _beginthreadex(NULL, 0, test_thread, &context, 0, NULL);
-    assert(thread != INVALID_HANDLE_VALUE);
+    check(thread != INVALID_HANDLE_VALUE);
     threads[i] = thread;
   }
 
@@ -87,7 +87,7 @@ static void run_test_iteration(void) {
   for (size_t i = 0; i < array_count(threads); i++) {
     HANDLE thread = threads[i];
     DWORD wr = WaitForSingleObject(thread, INFINITE);
-    assert(wr == WAIT_OBJECT_0);
+    check(wr == WAIT_OBJECT_0);
     CloseHandle(thread);
   }
 }
diff --git a/test/test-udp-pings.c b/test/test-udp-pings.c
index 58a07c0..d4875b2 100644
--- a/test/test-udp-pings.c
+++ b/test/test-udp-pings.c
@@ -1,8 +1,8 @@
-#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 
 #include "error.h"
+#include "test-util.h"
 #include "wepoll.h"
 #include "win.h"
 
@@ -24,43 +24,43 @@ int main(void) {
   struct epoll_event ev;
 
   epoll_hnd = epoll_create1(0);
-  assert(epoll_hnd && epoll_hnd != INVALID_HANDLE_VALUE);
+  check(epoll_hnd && epoll_hnd != INVALID_HANDLE_VALUE);
 
   srv = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
   r = ioctlsocket(srv, FIONBIO, &one);
-  assert(r == 0);
+  check(r == 0);
 
   address.sin_family = AF_INET;
   address.sin_port = htons(LISTEN_PORT);
   address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
   r = bind(srv, (struct sockaddr*) &address, sizeof address);
-  assert(r == 0);
+  check(r == 0);
 
   ev.events = EPOLLIN | EPOLLERR;
   ev.data.sock = srv;
   r = epoll_ctl(epoll_hnd, EPOLL_CTL_ADD, srv, &ev);
-  assert(r == 0);
+  check(r == 0);
 
   for (i = 0; i < NUM_PINGERS; i++) {
     SOCKET sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 
     r = ioctlsocket(sock, FIONBIO, &one);
-    assert(r == 0);
+    check(r == 0);
 
     r = setsockopt(
         sock, SOL_SOCKET, SO_REUSEADDR, (const char*) &one, sizeof one);
-    assert(r == 0);
+    check(r == 0);
 
     r = connect(sock, (struct sockaddr*) &address, sizeof address);
     /* Unlike unix, windows sets the error to EWOULDBLOCK when the connection
      * is being established in the background.
      */
-    assert(r == 0 || WSAGetLastError() == WSAEWOULDBLOCK);
+    check(r == 0 || WSAGetLastError() == WSAEWOULDBLOCK);
 
     ev.events = (uint32_t) EPOLLOUT | EPOLLERR | EPOLLONESHOT;
     ev.data.sock = sock;
     r = epoll_ctl(epoll_hnd, EPOLL_CTL_ADD, sock, &ev);
-    assert(r == 0);
+    check(r == 0);
   }
 
   ticks_start = GetTickCount();
@@ -86,7 +86,7 @@ int main(void) {
     }
 
     count = epoll_wait(epoll_hnd, events, 15, 1000);
-    assert(count >= 0);
+    check(count >= 0);
 
     for (i = 0; i < count; i++) {
       int revents = events[i].events;
@@ -97,11 +97,11 @@ int main(void) {
         int err_len = sizeof err;
 
         r = getsockopt(sock, SOL_SOCKET, SO_ERROR, (char*) &err, &err_len);
-        assert(r == 0);
+        check(r == 0);
         fprintf(stderr, "Socket error: %d\n", err);
 
         r = epoll_ctl(epoll_hnd, EPOLL_CTL_DEL, sock, NULL);
-        assert(r == 0);
+        check(r == 0);
         continue;
       }
 
@@ -119,8 +119,8 @@ int main(void) {
           r = WSARecv(sock, &wsa_buf, 1, &bytes, &flags, NULL, NULL);
           if (r == SOCKET_ERROR && WSAGetLastError() == WSAEWOULDBLOCK)
             break;
-          assert(r >= 0);
-          assert(bytes == sizeof PING);
+          check(r >= 0);
+          check(bytes == sizeof PING);
           pings++;
         }
 
@@ -135,8 +135,8 @@ int main(void) {
         wsa_buf.buf = (char*) PING;
         wsa_buf.len = sizeof PING;
         r = WSASend(sock, &wsa_buf, 1, &bytes, 0, NULL, NULL);
-        assert(r >= 0);
-        assert(bytes == sizeof PING);
+        check(r >= 0);
+        check(bytes == sizeof PING);
 
         pings_sent++;
 
@@ -150,12 +150,12 @@ int main(void) {
         continue;
       }
 
-      assert(0);
+      check(0);
     }
   }
 
   r = epoll_close(epoll_hnd);
-  assert(r == 0);
+  check(r == 0);
 
   closesocket(srv);