Add test for RecvStatus error_string API

test/core/end2end/tests/simple_request.cc

@@ -99,6 +99,7 @@ static void simple_request_body(grpc_end2end_test_config config,
   grpc_metadata_array request_metadata_recv;
   grpc_call_details call_details;
   grpc_status_code status;
+  const char* error_string;
   grpc_call_error error;
   grpc_slice details;
   int was_cancelled = 2;
@@ -148,6 +149,7 @@ static void simple_request_body(grpc_end2end_test_config config,
   op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv;
   op->data.recv_status_on_client.status = &status;
   op->data.recv_status_on_client.status_details = &details;
+  op->data.recv_status_on_client.error_string = &error_string;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
@@ -199,6 +201,16 @@ static void simple_request_body(grpc_end2end_test_config config,
 
   GPR_ASSERT(status == GRPC_STATUS_UNIMPLEMENTED);
   GPR_ASSERT(0 == grpc_slice_str_cmp(details, "xyz"));
+  // the following sanity check makes sure that the requested error string is 
+  // correctly populated by the core. It looks for certain substrings that are
+  // not likely to change much. Some parts of the error, like time created,
+  // obviously are not checked.
+  GPR_ASSERT(nullptr != strstr(error_string, "xyz"));
+  GPR_ASSERT(nullptr != strstr(error_string, "description"));
+  GPR_ASSERT(nullptr != strstr(error_string, "Error received from peer"));
+  GPR_ASSERT(nullptr != strstr(error_string, "src/core/lib/surface/call.cc"));
+  GPR_ASSERT(nullptr != strstr(error_string, "grpc_message"));
+  GPR_ASSERT(nullptr != strstr(error_string, "grpc_status"));  
   GPR_ASSERT(0 == grpc_slice_str_cmp(call_details.method, "/foo"));
   validate_host_override_string("foo.test.google.fr:1234", call_details.host,
                                 config);
@@ -206,6 +218,7 @@ static void simple_request_body(grpc_end2end_test_config config,
   GPR_ASSERT(was_cancelled == 1);
 
   grpc_slice_unref(details);
+  gpr_free((void*)error_string);
   grpc_metadata_array_destroy(&initial_metadata_recv);
   grpc_metadata_array_destroy(&trailing_metadata_recv);
   grpc_metadata_array_destroy(&request_metadata_recv);