diff --git a/test/cpp/interop/client.cc b/test/cpp/interop/client.cc
index 69d24299c6e..05bd90bcaba 100644
--- a/test/cpp/interop/client.cc
+++ b/test/cpp/interop/client.cc
@@ -111,8 +111,32 @@ grpc::string GetServiceAccountJsonKey() {
   return json_key;
 }
 
-void DoEmpty(std::shared_ptr<ChannelInterface> channel) {
+std::shared_ptr<ChannelInterface> CreateChannelForTestCase(
+    const grpc::string& test_case) {
+  GPR_ASSERT(FLAGS_server_port);
+  const int host_port_buf_size = 1024;
+  char host_port[host_port_buf_size];
+  snprintf(host_port, host_port_buf_size, "%s:%d", FLAGS_server_host.c_str(),
+           FLAGS_server_port);
+
+  if (test_case == "service_account_creds") {
+    std::unique_ptr<Credentials> creds;
+    GPR_ASSERT(FLAGS_enable_ssl);
+    grpc::string json_key = GetServiceAccountJsonKey();
+    creds = CredentialsFactory::ServiceAccountCredentials(
+        json_key, FLAGS_oauth_scope, std::chrono::seconds(3600));
+    return CreateTestChannel(host_port, FLAGS_server_host_override,
+                             FLAGS_enable_ssl, FLAGS_use_prod_roots, creds);
+  } else {
+    return CreateTestChannel(host_port, FLAGS_server_host_override,
+                             FLAGS_enable_ssl, FLAGS_use_prod_roots);
+  }
+}
+
+void DoEmpty() {
   gpr_log(GPR_INFO, "Sending an empty rpc...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("empty_unary");
   std::unique_ptr<TestService::Stub> stub(TestService::NewStub(channel));
 
   grpc::testing::Empty request = grpc::testing::Empty::default_instance();
@@ -125,43 +149,58 @@ void DoEmpty(std::shared_ptr<ChannelInterface> channel) {
   gpr_log(GPR_INFO, "Empty rpc done.");
 }
 
-void DoLargeUnary(std::shared_ptr<ChannelInterface> channel, bool auth) {
-  gpr_log(GPR_INFO, "Sending a large unary rpc...");
+void LargeUnaryShared(std::shared_ptr<ChannelInterface> channel,
+                      SimpleRequest* request, SimpleResponse* response) {
   std::unique_ptr<TestService::Stub> stub(TestService::NewStub(channel));
 
-  SimpleRequest request;
-  SimpleResponse response;
   ClientContext context;
-  request.set_response_type(grpc::testing::PayloadType::COMPRESSABLE);
-  request.set_response_size(kLargeResponseSize);
-  if (auth) {
-    request.set_fill_username(true);
-    request.set_fill_oauth_scope(true);
-  }
+  request->set_response_type(grpc::testing::PayloadType::COMPRESSABLE);
+  request->set_response_size(kLargeResponseSize);
   grpc::string payload(kLargeRequestSize, '\0');
-  request.mutable_payload()->set_body(payload.c_str(), kLargeRequestSize);
+  request->mutable_payload()->set_body(payload.c_str(), kLargeRequestSize);
 
-  grpc::Status s = stub->UnaryCall(&context, request, &response);
+  grpc::Status s = stub->UnaryCall(&context, *request, response);
 
   GPR_ASSERT(s.IsOk());
-  GPR_ASSERT(response.payload().type() ==
+  GPR_ASSERT(response->payload().type() ==
              grpc::testing::PayloadType::COMPRESSABLE);
-  GPR_ASSERT(response.payload().body() ==
+  GPR_ASSERT(response->payload().body() ==
              grpc::string(kLargeResponseSize, '\0'));
-  if (auth) {
-    GPR_ASSERT(!response.username().empty());
-    GPR_ASSERT(!response.oauth_scope().empty());
-    grpc::string json_key = GetServiceAccountJsonKey();
-    GPR_ASSERT(json_key.find(response.username()) != grpc::string::npos);
-    GPR_ASSERT(FLAGS_oauth_scope.find(response.oauth_scope()) !=
-               grpc::string::npos);
-  }
+}
+
+void DoServiceAccountCreds() {
+  gpr_log(GPR_INFO,
+          "Sending a large unary rpc with service account credentials ...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("service_account_creds");
+  SimpleRequest request;
+  SimpleResponse response;
+  request.set_fill_username(true);
+  request.set_fill_oauth_scope(true);
+  LargeUnaryShared(channel, &request, &response);
+  GPR_ASSERT(!response.username().empty());
+  GPR_ASSERT(!response.oauth_scope().empty());
+  grpc::string json_key = GetServiceAccountJsonKey();
+  GPR_ASSERT(json_key.find(response.username()) != grpc::string::npos);
+  GPR_ASSERT(FLAGS_oauth_scope.find(response.oauth_scope()) !=
+             grpc::string::npos);
+  gpr_log(GPR_INFO, "Large unary with service account creds done.");
+}
 
+void DoLargeUnary() {
+  gpr_log(GPR_INFO, "Sending a large unary rpc...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("large_unary");
+  SimpleRequest request;
+  SimpleResponse response;
+  LargeUnaryShared(channel, &request, &response);
   gpr_log(GPR_INFO, "Large unary done.");
 }
 
-void DoRequestStreaming(std::shared_ptr<ChannelInterface> channel) {
+void DoRequestStreaming() {
   gpr_log(GPR_INFO, "Sending request steaming rpc ...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("client_streaming");
   std::unique_ptr<TestService::Stub> stub(TestService::NewStub(channel));
 
   grpc::ClientContext context;
@@ -186,8 +225,10 @@ void DoRequestStreaming(std::shared_ptr<ChannelInterface> channel) {
   gpr_log(GPR_INFO, "Request streaming done.");
 }
 
-void DoResponseStreaming(std::shared_ptr<ChannelInterface> channel) {
+void DoResponseStreaming() {
   gpr_log(GPR_INFO, "Receiving response steaming rpc ...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("server_streaming");
   std::unique_ptr<TestService::Stub> stub(TestService::NewStub(channel));
 
   grpc::ClientContext context;
@@ -213,9 +254,10 @@ void DoResponseStreaming(std::shared_ptr<ChannelInterface> channel) {
   gpr_log(GPR_INFO, "Response streaming done.");
 }
 
-void DoResponseStreamingWithSlowConsumer(
-    std::shared_ptr<ChannelInterface> channel) {
+void DoResponseStreamingWithSlowConsumer() {
   gpr_log(GPR_INFO, "Receiving response steaming rpc with slow consumer ...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("slow_consumer");
   std::unique_ptr<TestService::Stub> stub(TestService::NewStub(channel));
 
   grpc::ClientContext context;
@@ -245,8 +287,10 @@ void DoResponseStreamingWithSlowConsumer(
   gpr_log(GPR_INFO, "Response streaming done.");
 }
 
-void DoHalfDuplex(std::shared_ptr<ChannelInterface> channel) {
+void DoHalfDuplex() {
   gpr_log(GPR_INFO, "Sending half-duplex streaming rpc ...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("half_duplex");
   std::unique_ptr<TestService::Stub> stub(TestService::NewStub(channel));
 
   grpc::ClientContext context;
@@ -276,8 +320,10 @@ void DoHalfDuplex(std::shared_ptr<ChannelInterface> channel) {
   gpr_log(GPR_INFO, "Half-duplex streaming rpc done.");
 }
 
-void DoPingPong(std::shared_ptr<ChannelInterface> channel) {
+void DoPingPong() {
   gpr_log(GPR_INFO, "Sending Ping Pong streaming rpc ...");
+  std::shared_ptr<ChannelInterface> channel =
+      CreateChannelForTestCase("ping_pong");
   std::unique_ptr<TestService::Stub> stub(TestService::NewStub(channel));
 
   grpc::ClientContext context;
@@ -312,57 +358,41 @@ int main(int argc, char** argv) {
 
   google::ParseCommandLineFlags(&argc, &argv, true);
 
-  GPR_ASSERT(FLAGS_server_port);
-  const int host_port_buf_size = 1024;
-  char host_port[host_port_buf_size];
-  snprintf(host_port, host_port_buf_size, "%s:%d", FLAGS_server_host.c_str(),
-           FLAGS_server_port);
-
-  std::shared_ptr<ChannelInterface> channel(
-      CreateTestChannel(host_port, FLAGS_server_host_override, FLAGS_enable_ssl,
-                        FLAGS_use_prod_roots));
-
   if (FLAGS_test_case == "empty_unary") {
-    DoEmpty(channel);
+    DoEmpty();
   } else if (FLAGS_test_case == "large_unary") {
-    DoLargeUnary(channel, false);
+    DoLargeUnary();
   } else if (FLAGS_test_case == "client_streaming") {
-    DoRequestStreaming(channel);
+    DoRequestStreaming();
   } else if (FLAGS_test_case == "server_streaming") {
-    DoResponseStreaming(channel);
+    DoResponseStreaming();
   } else if (FLAGS_test_case == "slow_consumer") {
-    DoResponseStreamingWithSlowConsumer(channel);
+    DoResponseStreamingWithSlowConsumer();
   } else if (FLAGS_test_case == "half_duplex") {
-    DoHalfDuplex(channel);
+    DoHalfDuplex();
   } else if (FLAGS_test_case == "ping_pong") {
-    DoPingPong(channel);
+    DoPingPong();
   } else if (FLAGS_test_case == "service_account_creds") {
-    std::unique_ptr<Credentials> creds;
-    GPR_ASSERT(FLAGS_enable_ssl);
-    grpc::string json_key = GetServiceAccountJsonKey();
-    creds = CredentialsFactory::ServiceAccountCredentials(
-        json_key, FLAGS_oauth_scope, std::chrono::seconds(3600));
-    std::shared_ptr<ChannelInterface> auth_channel(
-        CreateTestChannel(host_port, FLAGS_server_host_override,
-                          FLAGS_enable_ssl, FLAGS_use_prod_roots, creds));
-    DoLargeUnary(auth_channel, true);
+    DoServiceAccountCreds();
   } else if (FLAGS_test_case == "all") {
-    DoEmpty(channel);
-    DoLargeUnary(channel, false);
-    DoRequestStreaming(channel);
-    DoResponseStreaming(channel);
-    DoHalfDuplex(channel);
-    DoPingPong(channel);
-    // TODO(yangg) add service_account_creds?
+    DoEmpty();
+    DoLargeUnary();
+    DoRequestStreaming();
+    DoResponseStreaming();
+    DoHalfDuplex();
+    DoPingPong();
+    if (FLAGS_enable_ssl) {
+      DoServiceAccountCreds();
+    }
   } else {
     gpr_log(
         GPR_ERROR,
         "Unsupported test case %s. Valid options are all|empty_unary|"
-        "large_unary|client_streaming|server_streaming|half_duplex|ping_pong",
+        "large_unary|client_streaming|server_streaming|half_duplex|ping_pong|"
+        "service_account_creds",
         FLAGS_test_case.c_str());
   }
 
-  channel.reset();
   grpc_shutdown();
   return 0;
 }