Add a macro to enable replacing the default with a custom port picker

include/grpc/support/port_platform.h

@@ -199,7 +199,7 @@
 #endif
 
 #if defined(GPR_POSIX_SOCKET) + defined(GPR_WIN32) != 1
-#error Must define exactly one of GPR_POSIX_POLLSET, GPR_WIN32
+#error Must define exactly one of GPR_POSIX_SOCKET, GPR_WIN32
 #endif
 
 typedef int16_t gpr_int16;

test/core/util/port_posix.c

@@ -32,7 +32,8 @@
  */
 
 #include <grpc/support/port_platform.h>
-#ifdef GPR_POSIX_SOCKET
+#include "test/core/util/test_config.h"
+#if defined(GPR_POSIX_SOCKET) && defined(GRPC_TEST_PICK_PORT)
 
 #include "test/core/util/port.h"
 
@@ -155,4 +156,4 @@ int grpc_pick_unused_port_or_die(void) {
   return port;
 }
 
-#endif /* GPR_POSIX_SOCKET */
+#endif /* GPR_POSIX_SOCKET && GRPC_TEST_PICK_PORT */

test/core/util/test_config.h

@@ -59,6 +59,10 @@ extern "C" {
   gpr_time_add(gpr_now(),                  \
                gpr_time_from_micros(GRPC_TEST_SLOWDOWN_FACTOR * 1e3 * (x)))
 
+#ifndef GRPC_TEST_CUSTOM_PICK_PORT
+#define GRPC_TEST_PICK_PORT
+#endif
+
 void grpc_test_init(int argc, char **argv);
 
 #ifdef __cplusplus