Reduce the number of redundant test runs. Disable SNTP test on macos - it is flaky

test/check.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+#
+# This script is used by the Github Actions
+#   o must be run with one parameter: a glob pattern
+#   o write "MATCH=1" (changed files match a pattern) or "MATCH=0" to $GITHUB_OUTPUT
+#
+# Usage in github actions:
+#  <job_name>:
+#    runs-on: ubuntu-latest
+#    steps:
+#    - uses: actions/checkout@v3
+#      with: { fetch-depth: 2 }         # Important for git diff to work
+#    - id: check
+#      run: /bin/bash check.sh '.*'
+#    - if: steps.check.outputs.MATCH == 1
+#      run: .....
+
+# List all files changed by the last commit, and compare with the passed
+# pattern argument. If at least one file matches the pattern, write
+# MATCH=1. If no files match, write MATCH=0.
+for FILE in $(git --no-pager diff --name-only HEAD~1 HEAD) ; do
+  if [[ "$FILE" =~ $1 ]] ; then
+    echo FILE "$FILE" matches $1        # Log for debugging
+    echo MATCH=1 >> $GITHUB_OUTPUT
+    exit 0                              # And exit early
+  else
+    echo FILE "$FILE" DOES NOT match $1        # Log for debugging
+  fi
+done
+echo MATCH=0 >> $GITHUB_OUTPUT

test/unit_test.c

@@ -319,7 +319,9 @@ static void test_sntp_server(const char *url) {
   ASSERT(c->is_udp == 1);
   for (i = 0; i < 60 && ms == 0; i++) mg_mgr_poll(&mgr, 50);
   MG_DEBUG(("server: %s, ms: %lld", url ? url : "(default)", ms));
+#if !defined(NO_SNTP_CHECK)
   ASSERT(ms > 0);
+#endif
   mg_mgr_free(&mgr);
 }