Create test protos in reusable free functions and make testing decryptor visible.

willow/src/api/BUILD

@@ -184,14 +184,13 @@ cc_test(
     srcs = ["client_test.cc"],
     deps = [
         ":client_cc",
-        ":client_cxx",
         "@googletest//:gtest_main",
         "@abseil-cpp//absl/status",
-        "@cxx.rs//:core",
         "//ffi_utils:status_matchers",
         "//willow/proto/willow:aggregation_config_cc_proto",
         "//willow/proto/willow:input_spec_cc_proto",
         "//willow/src/input_encoding:codec",
         "//willow/src/testing_utils:shell_testing_decryptor_cc",
+        "//willow/src/testing_utils:testing_utils_cc",
     ],
 )

willow/src/api/client_test.cc

@@ -18,7 +18,6 @@
 
 #include <memory>
 #include <string>
-#include <vector>
 
 #include "absl/status/status.h"
 #include "ffi_utils/status_matchers.h"
@@ -29,6 +28,7 @@
 #include "willow/src/input_encoding/codec.h"
 #include "willow/src/input_encoding/codec_factory.h"
 #include "willow/src/testing_utils/shell_testing_decryptor.h"
+#include "willow/src/testing_utils/testing_utils.h"
 
 namespace secure_aggregation {
 namespace willow {
@@ -41,49 +41,13 @@ using ::testing::ElementsAreArray;
 using ::testing::Pair;
 using ::testing::UnorderedElementsAre;
 
-AggregationConfigProto CreateTestConfig() {
-  AggregationConfigProto config;
-  VectorConfig vector_config;
-  vector_config.set_length(8);  // 4 countries x 2 languages
-  vector_config.set_bound(100);
-  (*config.mutable_vector_configs())["metric1"] = vector_config;
-  config.set_max_number_of_decryptors(1);
-  config.set_max_number_of_clients(10);
-  config.set_key_id("test");
-  return config;
-}
-
 TEST(WillowShellClientTest, InitializeAndGenerateContribution) {
-  AggregationConfigProto config = CreateTestConfig();
+  AggregationConfigProto config = CreateTestAggregationConfigProto();
 
   // Create and encode input.
-  MetricData metric_data;
-  metric_data["metric1"] = {10, 20, 5};
-  GroupData group_by_data;
-  group_by_data["country"] = {"US", "CA", "US"};
-  group_by_data["lang"] = {"en", "es", "es"};
-  InputSpec input_spec;
-  auto* metric_spec = input_spec.add_metric_vector_specs();
-  metric_spec->set_vector_name("metric1");
-  metric_spec->set_data_type(InputSpec::INT64);
-  auto* group_by_spec1 = input_spec.add_group_by_vector_specs();
-  group_by_spec1->set_vector_name("country");
-  group_by_spec1->set_data_type(InputSpec::STRING);
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "CA");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "GB");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "MX");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "US");
-  auto* group_by_spec2 = input_spec.add_group_by_vector_specs();
-  group_by_spec2->set_vector_name("lang");
-  group_by_spec2->set_data_type(InputSpec::STRING);
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "en");
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "es");
+  MetricData metric_data = CreateTestMetricData();
+  GroupData group_by_data = CreateTestGroupData();
+  InputSpec input_spec = CreateTestInputSpecProto();
   SECAGG_ASSERT_OK_AND_ASSIGN(std::unique_ptr<Codec> encoder,
                               CodecFactory::CreateExplicitCodec(input_spec));
   SECAGG_ASSERT_OK_AND_ASSIGN(EncodedData encoded_data,
@@ -129,7 +93,7 @@ TEST(WillowShellClientTest, InitializeAndGenerateContribution) {
 }
 
 TEST(WillowShellClientTest, EmptyEncodedData) {
-  AggregationConfigProto config = CreateTestConfig();
+  AggregationConfigProto config = CreateTestAggregationConfigProto();
 
   // Create empty encoded data.
   EncodedData encoded_data;
@@ -151,7 +115,7 @@ TEST(WillowShellClientTest, EmptyEncodedData) {
 
 TEST(WillowShellClientTest, InvalidAggregationConfig) {
   // Originally valid config.
-  AggregationConfigProto config = CreateTestConfig();
+  AggregationConfigProto config = CreateTestAggregationConfigProto();
 
   // Create encoded data directly.
   EncodedData encoded_data = {{"metric1", {0, 20, 0, 0, 0, 0, 10, 5}}};

willow/src/input_encoding/BUILD

@@ -51,5 +51,6 @@ cc_test(
         "@abseil-cpp//absl/status",
         "//ffi_utils:status_matchers",
         "//willow/proto/willow:input_spec_cc_proto",
+        "//willow/src/testing_utils:testing_utils_cc",
     ],
 )

willow/src/input_encoding/explicit_codec_test.cc

@@ -24,6 +24,7 @@
 #include "willow/proto/willow/input_spec.pb.h"
 #include "willow/src/input_encoding/codec.h"
 #include "willow/src/input_encoding/codec_factory.h"
+#include "willow/src/testing_utils/testing_utils.h"
 
 namespace secure_aggregation {
 namespace willow {
@@ -298,33 +299,9 @@ TEST(CodecFactoryTest, ValidateInputAndSpecCustomGlobalDomainSize) {
 }
 
 TEST(CodecFactoryTest, EncodeSimpleGroupBy) {
-  MetricData metric_data;
-  metric_data["metric1"] = {10, 20, 5};
-  GroupData group_by_data;
-  group_by_data["country"] = {"US", "CA", "US"};
-  group_by_data["lang"] = {"en", "es", "es"};
-  InputSpec input_spec;
-  auto* metric_spec = input_spec.add_metric_vector_specs();
-  metric_spec->set_vector_name("metric1");
-  metric_spec->set_data_type(InputSpec::INT64);
-  auto* group_by_spec1 = input_spec.add_group_by_vector_specs();
-  group_by_spec1->set_vector_name("country");
-  group_by_spec1->set_data_type(InputSpec::STRING);
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "CA");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "GB");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "MX");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "US");
-  auto* group_by_spec2 = input_spec.add_group_by_vector_specs();
-  group_by_spec2->set_vector_name("lang");
-  group_by_spec2->set_data_type(InputSpec::STRING);
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "en");
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "es");
+  InputSpec input_spec = CreateTestInputSpecProto();
+  MetricData metric_data = CreateTestMetricData();
+  GroupData group_by_data = CreateTestGroupData();
 
   // group_by keys are sorted: "country", "lang"
   // value_to_index_maps["country"]: {"CA":0, "GB":1, "MX":2, "US":3}
@@ -402,33 +379,9 @@ TEST(CodecFactoryTest, EncodeTwoMetricsOneGroupBy) {
 }
 
 TEST(CodecFactoryTest, EncodeThenDecode) {
-  MetricData metric_data;
-  metric_data["metric1"] = {10, 20, 5};
-  GroupData group_by_data;
-  group_by_data["country"] = {"US", "CA", "US"};
-  group_by_data["lang"] = {"en", "es", "es"};
-  InputSpec input_spec;
-  auto* metric_spec = input_spec.add_metric_vector_specs();
-  metric_spec->set_vector_name("metric1");
-  metric_spec->set_data_type(InputSpec::INT64);
-  auto* group_by_spec1 = input_spec.add_group_by_vector_specs();
-  group_by_spec1->set_vector_name("country");
-  group_by_spec1->set_data_type(InputSpec::STRING);
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "CA");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "GB");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "MX");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "US");
-  auto* group_by_spec2 = input_spec.add_group_by_vector_specs();
-  group_by_spec2->set_vector_name("lang");
-  group_by_spec2->set_data_type(InputSpec::STRING);
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "en");
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "es");
+  InputSpec input_spec = CreateTestInputSpecProto();
+  MetricData metric_data = CreateTestMetricData();
+  GroupData group_by_data = CreateTestGroupData();
 
   SECAGG_ASSERT_OK_AND_ASSIGN(std::unique_ptr<Codec> encoder,
                               CodecFactory::CreateExplicitCodec(input_spec));
@@ -457,33 +410,9 @@ TEST(CodecFactoryTest, EncodeThenDecode) {
 }
 
 TEST(CodecFactoryTest, EncodeThenDecodeDataOrderDoesNotMatter) {
-  MetricData metric_data1;
-  metric_data1["metric1"] = {10, 20, 5};
-  GroupData group_by_data1;
-  group_by_data1["lang"] = {"en", "es", "es"};
-  group_by_data1["country"] = {"US", "CA", "US"};
-  InputSpec input_spec;
-  auto* metric_spec = input_spec.add_metric_vector_specs();
-  metric_spec->set_vector_name("metric1");
-  metric_spec->set_data_type(InputSpec::INT64);
-  auto* group_by_spec1 = input_spec.add_group_by_vector_specs();
-  group_by_spec1->set_vector_name("lang");
-  group_by_spec1->set_data_type(InputSpec::STRING);
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "en");
-  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
-      "es");
-  auto* group_by_spec2 = input_spec.add_group_by_vector_specs();
-  group_by_spec2->set_vector_name("country");
-  group_by_spec2->set_data_type(InputSpec::STRING);
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "CA");
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "GB");
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "MX");
-  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
-      "US");
+  InputSpec input_spec = CreateTestInputSpecProto();
+  MetricData metric_data1 = CreateTestMetricData();
+  GroupData group_by_data1 = CreateTestGroupData();
 
   SECAGG_ASSERT_OK_AND_ASSIGN(std::unique_ptr<Codec> encoder1,
                               CodecFactory::CreateExplicitCodec(input_spec));

willow/src/testing_utils/BUILD

@@ -131,6 +131,7 @@ cc_library(
     name = "shell_testing_decryptor_cc",
     srcs = ["shell_testing_decryptor.cc"],
     hdrs = ["shell_testing_decryptor.h"],
+    visibility = ["//visibility:public"],
     deps = [
         ":shell_testing_decryptor_cxx",
         "@abseil-cpp//absl/memory",
@@ -157,3 +158,15 @@ cc_test(
         "//willow/proto/willow:aggregation_config_cc_proto",
     ],
 )
+
+cc_library(
+    name = "testing_utils_cc",
+    srcs = ["testing_utils.cc"],
+    hdrs = ["testing_utils.h"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//willow/proto/willow:aggregation_config_cc_proto",
+        "//willow/proto/willow:input_spec_cc_proto",
+        "//willow/src/input_encoding:codec",
+    ],
+)

willow/src/testing_utils/testing_utils.cc

@@ -0,0 +1,74 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "willow/src/testing_utils/testing_utils.h"
+
+#include "willow/src/input_encoding/codec.h"
+
+namespace secure_aggregation::willow {
+
+AggregationConfigProto CreateTestAggregationConfigProto() {
+  AggregationConfigProto config;
+  VectorConfig vector_config;
+  vector_config.set_length(8);  // 4 countries x 2 languages
+  vector_config.set_bound(100);
+  (*config.mutable_vector_configs())["metric1"] = vector_config;
+  config.set_max_number_of_decryptors(1);
+  config.set_max_number_of_clients(10);
+  config.set_key_id("test");
+  return config;
+}
+
+InputSpec CreateTestInputSpecProto() {
+  InputSpec input_spec;
+  auto* metric_spec = input_spec.add_metric_vector_specs();
+  metric_spec->set_vector_name("metric1");
+  metric_spec->set_data_type(InputSpec::INT64);
+  metric_spec->mutable_domain_spec()->mutable_interval()->set_min(0);
+  metric_spec->mutable_domain_spec()->mutable_interval()->set_max(100);
+  auto* group_by_spec1 = input_spec.add_group_by_vector_specs();
+  group_by_spec1->set_vector_name("country");
+  group_by_spec1->set_data_type(InputSpec::STRING);
+  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
+      "CA");
+  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
+      "GB");
+  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
+      "MX");
+  group_by_spec1->mutable_domain_spec()->mutable_string_values()->add_values(
+      "US");
+  auto* group_by_spec2 = input_spec.add_group_by_vector_specs();
+  group_by_spec2->set_vector_name("lang");
+  group_by_spec2->set_data_type(InputSpec::STRING);
+  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
+      "en");
+  group_by_spec2->mutable_domain_spec()->mutable_string_values()->add_values(
+      "es");
+  return input_spec;
+}
+
+MetricData CreateTestMetricData() {
+  MetricData metric_data;
+  metric_data["metric1"] = {10, 20, 5};
+  return metric_data;
+}
+
+GroupData CreateTestGroupData() {
+  GroupData group_by_data;
+  group_by_data["country"] = {"US", "CA", "US"};
+  group_by_data["lang"] = {"en", "es", "es"};
+  return group_by_data;
+}
+
+}  // namespace secure_aggregation::willow

willow/src/testing_utils/testing_utils.h

@@ -0,0 +1,38 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef SECURE_AGGREGATION_WILLOW_SRC_TESTING_UTILS_TESTING_UTILS_H_
+#define SECURE_AGGREGATION_WILLOW_SRC_TESTING_UTILS_TESTING_UTILS_H_
+
+#include "willow/proto/willow/aggregation_config.pb.h"
+#include "willow/proto/willow/input_spec.pb.h"
+#include "willow/src/input_encoding/codec.h"
+
+namespace secure_aggregation::willow {
+
+// Returns a test AggregationConfigProto.
+AggregationConfigProto CreateTestAggregationConfigProto();
+
+// Returns a test InputSpec proto with one metric and two group-by vectors.
+InputSpec CreateTestInputSpecProto();
+
+// Returns a test MetricData with one metric.
+MetricData CreateTestMetricData();
+
+// Returns a test GroupData with two group-by vectors.
+GroupData CreateTestGroupData();
+
+}  // namespace secure_aggregation::willow
+
+#endif  // SECURE_AGGREGATION_WILLOW_SRC_TESTING_UTILS_TESTING_UTILS_H_