Add test to ssl-opt.sh demonstrating the need for ssl_check_pending
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 4c65121..4afc527 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -2568,6 +2568,19 @@
"$P_CLI dtls=1 event=1 tickets=0 reconnect=1" \
0 \
-c "Read from server: .* bytes read"
+
+# This test demonstrates the need for the mbedtls_ssl_check_pending function.
+# During session resumption, the client will send its ApplicationData record
+# within the same datagram as the Finished messages. In this situation, the
+# server MUST NOT idle on the underlying transport after handshake completion,
+# because the ApplicationData request has already been queued internally.
+run_test "Event-driven I/O, DTLS: session-id resume, UDP packing" \
+ -p "$P_PXY pack=10" \
+ "$P_SRV dtls=1 event=1 tickets=0 auth_mode=required" \
+ "$P_CLI dtls=1 event=1 tickets=0 reconnect=1" \
+ 0 \
+ -c "Read from server: .* bytes read"
+
# Tests for version negotiation
run_test "Version check: all -> 1.2" \