libtest: fix MSVC warning C4706

With warning level 4, MSVC warns about assignments within conditional
expressions. Change the while loop to a do-while loop to fix this. This
change is also consistent with CODE_STYLE.md.

3 files changed, 12 insertions, 9 deletions

diff --git a/tests/libtest/lib1515.c b/tests/libtest/lib1515.c
index 7763c2233..c1499381a 100644
--- a/tests/libtest/lib1515.c
+++ b/tests/libtest/lib1515.c
@@ -95,12 +95,13 @@ static int do_one_request(CURLM *m, char *URL, char *resolve)
     abort_on_test_timeout();
   }
 
-  while((msg = curl_multi_info_read(m, &msgs_left))) {
-    if(msg->msg == CURLMSG_DONE && msg->easy_handle == curls) {
+  do {
+    msg = curl_multi_info_read(m, &msgs_left);
+    if(msg && msg->msg == CURLMSG_DONE && msg->easy_handle == curls) {
       res = msg->data.result;
       break;
     }
-  }
+  } while(msg);
 
 test_cleanup:
 
diff --git a/tests/libtest/lib1531.c b/tests/libtest/lib1531.c
index e6386b264..287acd6c6 100644
--- a/tests/libtest/lib1531.c
+++ b/tests/libtest/lib1531.c
@@ -127,12 +127,13 @@ int test(char *URL)
   } while(still_running);
 
   /* See how the transfers went */
-  while((msg = curl_multi_info_read(multi_handle, &msgs_left))) {
-    if(msg->msg == CURLMSG_DONE) {
+  do {
+    msg = curl_multi_info_read(multi_handle, &msgs_left);
+    if(msg && msg->msg == CURLMSG_DONE) {
       printf("HTTP transfer completed with status %d\n", msg->data.result);
       break;
     }
-  }
+  } while(msg);
 
   curl_multi_cleanup(multi_handle);
 
diff --git a/tests/libtest/lib1900.c b/tests/libtest/lib1900.c
index b55f3b7d8..cac1dd1d9 100644
--- a/tests/libtest/lib1900.c
+++ b/tests/libtest/lib1900.c
@@ -189,8 +189,9 @@ int test(char *URL)
     abort_on_test_timeout();
 
     /* See how the transfers went */
-    while((msg = curl_multi_info_read(m, &msgs_left))) {
-      if(msg->msg == CURLMSG_DONE) {
+    do {
+      msg = curl_multi_info_read(m, &msgs_left);
+      if(msg && msg->msg == CURLMSG_DONE) {
         int i, found = 0;
 
         /* Find out which handle this message is about */
@@ -203,7 +204,7 @@ int test(char *URL)
         printf("Handle %d Completed with status %d\n", i, msg->data.result);
         curl_multi_remove_handle(m, handles[i]);
       }
-    }
+    } while(msg);
 
     if(handlenum == num_handles && !running) {
       break; /* done */