Experimental method to get a debugging only view into credentials

include/grpcpp/impl/codegen/client_context_impl.h

@@ -316,6 +316,13 @@ class ClientContext {
   void set_credentials(
       const std::shared_ptr<grpc_impl::CallCredentials>& creds);
 
+  /// EXPERIMENTAL debugging API
+  ///
+  /// Returns the credentials for the client call. This should be used only in
+  /// tests and for diagnostic purposes, and should not be used by application
+  /// logic.
+  std::shared_ptr<grpc_impl::CallCredentials> credentials() { return creds_; }
+
   /// Return the compression algorithm the client call will request be used.
   /// Note that the gRPC runtime may decide to ignore this request, for example,
   /// due to resource constraints.

test/cpp/end2end/end2end_test.cc

@@ -1884,6 +1884,7 @@ TEST_P(SecureEnd2endTest, CallCredentialsInterceptionWithSetCredentials) {
   std::shared_ptr<CallCredentials> creds1 =
       GoogleIAMCredentials("wrong_token", "wrong_selector");
   context.set_credentials(creds1);
+  EXPECT_EQ(context.credentials(), creds1);
   request.set_message("Hello");
   request.mutable_param()->set_echo_metadata(true);
 
@@ -1907,9 +1908,11 @@ TEST_P(SecureEnd2endTest, OverridePerCallCredentials) {
   std::shared_ptr<CallCredentials> creds1 =
       GoogleIAMCredentials("fake_token1", "fake_selector1");
   context.set_credentials(creds1);
+  EXPECT_EQ(context.credentials(), creds1);
   std::shared_ptr<CallCredentials> creds2 =
       GoogleIAMCredentials("fake_token2", "fake_selector2");
   context.set_credentials(creds2);
+  EXPECT_EQ(context.credentials(), creds2);
   request.set_message("Hello");
   request.mutable_param()->set_echo_metadata(true);