Support datagrams in QuicTransport.

gfe-relnote: n/a (no functional change to production code)
PiperOrigin-RevId: 288493541
Change-Id: I6d2a791ae062701ad4b9fb650ab267566373675f
diff --git a/quic/quic_transport/quic_transport_client_session_test.cc b/quic/quic_transport/quic_transport_client_session_test.cc
index 613ef17..3e08bf5 100644
--- a/quic/quic_transport/quic_transport_client_session_test.cc
+++ b/quic/quic_transport/quic_transport_client_session_test.cc
@@ -168,6 +168,17 @@
   EXPECT_EQ(stream->id(), id);
 }
 
+TEST_F(QuicTransportClientSessionTest, ReceiveDatagram) {
+  QuicOptional<std::string> datagram = session_->ReadDatagram();
+  EXPECT_FALSE(datagram.has_value());
+
+  EXPECT_CALL(visitor_, OnIncomingDatagramAvailable());
+  session_->OnMessageReceived("test");
+  datagram = session_->ReadDatagram();
+  ASSERT_TRUE(datagram.has_value());
+  EXPECT_EQ("test", *datagram);
+}
+
 }  // namespace
 }  // namespace test
 }  // namespace quic