test(common): add an IsProtoApproximatelyEqual matcher (#13873)

devbww · web-flow · commit eaeff36a59db · 2024-03-28T17:26:12.000-04:00
Add a proto-message matcher that supports approximate equality
checks on floating-point fields.
diff --git a/google/cloud/testing_util/is_proto_equal.cc b/google/cloud/testing_util/is_proto_equal.cc
@@ -27,7 +27,39 @@ absl::optional<std::string> CompareProtos(
   google::protobuf::util::MessageDifferencer differencer;
   differencer.ReportDifferencesToString(&delta);
   auto const result = differencer.Compare(arg, value);
-  if (result) return {};
+  if (result) return absl::nullopt;
+  return delta;
+}
+
+absl::optional<std::string> CompareProtosApproximately(
+    google::protobuf::Message const& arg,
+    google::protobuf::Message const& value) {
+  std::string delta;
+  google::protobuf::util::DefaultFieldComparator comparator;
+  comparator.set_float_comparison(
+      google::protobuf::util::DefaultFieldComparator::APPROXIMATE);
+  // Keep the comparator's default fraction and margin.
+  google::protobuf::util::MessageDifferencer differencer;
+  differencer.set_field_comparator(&comparator);
+  differencer.ReportDifferencesToString(&delta);
+  auto const result = differencer.Compare(arg, value);
+  if (result) return absl::nullopt;
+  return delta;
+}
+
+absl::optional<std::string> CompareProtosApproximately(
+    google::protobuf::Message const& arg,
+    google::protobuf::Message const& value, double fraction, double margin) {
+  std::string delta;
+  google::protobuf::util::DefaultFieldComparator comparator;
+  comparator.set_float_comparison(
+      google::protobuf::util::DefaultFieldComparator::APPROXIMATE);
+  comparator.SetDefaultFractionAndMargin(fraction, margin);
+  google::protobuf::util::MessageDifferencer differencer;
+  differencer.set_field_comparator(&comparator);
+  differencer.ReportDifferencesToString(&delta);
+  auto const result = differencer.Compare(arg, value);
+  if (result) return absl::nullopt;
   return delta;
 }
 
diff --git a/google/cloud/testing_util/is_proto_equal.h b/google/cloud/testing_util/is_proto_equal.h
@@ -38,6 +38,37 @@ MATCHER_P(IsProtoEqual, value, "Checks whether protos are equal") {
   return !delta.has_value();
 }
 
+// Compares float and double fields approximately, using the default
+// google::protobuf::MessageDifferencer tolerances.
+absl::optional<std::string> CompareProtosApproximately(
+    google::protobuf::Message const& arg,
+    google::protobuf::Message const& value);
+
+MATCHER_P(IsProtoApproximatelyEqual, value,
+          "Checks whether protos are approximately equal") {
+  absl::optional<std::string> delta = CompareProtosApproximately(arg, value);
+  if (delta.has_value()) {
+    *result_listener << "\n" << *delta;
+  }
+  return !delta.has_value();
+}
+
+// Compares float and double fields approximately, using the given
+// @p fraction and @p margin.
+absl::optional<std::string> CompareProtosApproximately(
+    google::protobuf::Message const& arg,
+    google::protobuf::Message const& value, double fraction, double margin);
+
+MATCHER_P3(IsProtoApproximatelyEqual, value, fraction, margin,
+           "Checks whether protos are approximately equal") {
+  absl::optional<std::string> delta =
+      CompareProtosApproximately(arg, value, fraction, margin);
+  if (delta.has_value()) {
+    *result_listener << "\n" << *delta;
+  }
+  return !delta.has_value();
+}
+
 }  // namespace testing_util
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END
 }  // namespace cloud
