diff --git a/quic/test_tools/quic_test_client.cc b/quic/test_tools/quic_test_client.cc
index d4608ed..3e577a3 100644
--- a/quic/test_tools/quic_test_client.cc
+++ b/quic/test_tools/quic_test_client.cc
@@ -210,7 +210,9 @@
           QuicWrapUnique(
               new RecordingProofVerifier(std::move(proof_verifier)))),
       override_server_connection_id_(EmptyQuicConnectionId()),
-      server_connection_id_overridden_(false) {}
+      server_connection_id_overridden_(false),
+      override_client_connection_id_(EmptyQuicConnectionId()),
+      client_connection_id_overridden_(false) {}
 
 MockableQuicClient::~MockableQuicClient() {
   if (connected()) {
@@ -242,6 +244,17 @@
   override_server_connection_id_ = server_connection_id;
 }
 
+QuicConnectionId MockableQuicClient::GetClientConnectionId() {
+  return client_connection_id_overridden_ ? override_client_connection_id_
+                                          : QuicClient::GetClientConnectionId();
+}
+
+void MockableQuicClient::UseClientConnectionId(
+    QuicConnectionId client_connection_id) {
+  client_connection_id_overridden_ = true;
+  override_client_connection_id_ = client_connection_id;
+}
+
 void MockableQuicClient::UseWriter(QuicPacketWriterWrapper* writer) {
   mockable_network_helper()->UseWriter(writer);
 }
@@ -756,6 +769,12 @@
   client_->UseConnectionId(server_connection_id);
 }
 
+void QuicTestClient::UseClientConnectionId(
+    QuicConnectionId client_connection_id) {
+  DCHECK(!connected());
+  client_->UseClientConnectionId(client_connection_id);
+}
+
 bool QuicTestClient::MigrateSocket(const QuicIpAddress& new_host) {
   return client_->MigrateSocket(new_host);
 }