Add gtest macros and matchers for Result<T> and Error.

Summary: Adds matcher support for Result and Error types, similar to absl::Status.

Differential Revision: D77409312

Author: Hardik Sharma

runtime/core/testing_util/TARGETS

@@ -0,0 +1,8 @@
+# Any targets that should be shared between fbcode and xplat must be defined in
+# targets.bzl. This file can contain fbcode-only targets.
+
+load(":targets.bzl", "define_common_targets")
+
+oncall("executorch")
+
+define_common_targets()

runtime/core/testing_util/error_matchers.h

@@ -0,0 +1,287 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @file
+ * Testing utilities for working with `executorch::runtime::Result<T>`.
+ *
+ * Defines the following utilities:
+ *
+ *   ===============
+ *   `IsOkAndHolds(m)`
+ *   ===============
+ *
+ *   This gMock matcher matches a Result<T> value whose error is Ok
+ *   and whose inner value matches matcher m.  Example:
+ *
+ *   ```
+ *   using ::testing::MatchesRegex;
+ *   using ::executorch::runtime::testing::IsOkAndHolds;
+ *   ...
+ *   executorch::runtime::Result<string> maybe_name = ...;
+ *   EXPECT_THAT(maybe_name, IsOkAndHolds(MatchesRegex("John .*")));
+ *   ```
+ *
+ *   ===============
+ *   `ErrorIs(Error::error_code)`
+ *   ===============
+ *
+ *   This gMock matcher matches a Result<T> value whose error matches
+ *   the given error matcher. Example:
+ *
+ *   ```
+ *   using ::executorch::runtime::testing::ErrorIs;
+ *   ...
+ *   executorch::runtime::Result<string> maybe_name = ...;
+ *   EXPECT_THAT(maybe_name, ErrorIs(Error::InvalidArgument));
+ *   ```
+ *
+ *   ===============
+ *   `IsOk()`
+ *   ===============
+ *
+ *   Matches an `executorch::runtime::Result<T>` value whose error value
+ *   is `executorch::runtime::Error::Ok`.
+ *
+ *   Example:
+ *   ```
+ *   using ::executorch::runtime::testing::IsOk;
+ *   ...
+ *   executorch::runtime::Result<string> maybe_name = ...;
+ *   EXPECT_THAT(maybe_name, IsOk());
+ *   ```
+ */
+
+#pragma once
+
+#include <ostream>
+#include <type_traits>
+#include <utility>
+
+#include "executorch/runtime/core/result.h"
+#include "gmock/gmock.h"
+
+/**
+ * Unwrap a Result to obtain its value. If the Result contains an error,
+ * fail the test with ASSERT_TRUE.
+ *
+ * This macro is useful for test code where you want to extract the value
+ * from a Result and fail the test if the Result contains an error.
+ *
+ * Example usage:
+ * ```
+ *   Result<int> maybe_value = GetSomeValue();
+ *   int value = ASSERT_OK_AND_UNWRAP(maybe_value);
+ *   // Use value...
+ * ```
+ *
+ * @param[in] result__ Expression yielding the Result to unwrap.
+ */
+#define ASSERT_OK_AND_UNWRAP(result__) \
+  ({                                   \
+    auto&& et_result__ = (result__);   \
+    ASSERT_TRUE(et_result__.ok());     \
+    std::move(*et_result__);           \
+  })
+
+namespace executorch {
+namespace runtime {
+namespace testing {
+
+namespace internal {
+
+// Helper function to get the error from a Result
+template <typename T>
+inline Error GetError(const Result<T>& result) {
+  return result.error();
+}
+
+// Helper function to get the error from a raw Error (identity function)
+inline Error GetError(const Error& error) {
+  return error;
+}
+
+////////////////////////////////////////////////////////////
+// Implementation of IsOkAndHolds().
+
+// Monomorphic implementation of matcher IsOkAndHolds(m). ResultType is a
+// reference to Result<T>.
+template <typename ResultType>
+class IsOkAndHoldsMatcherImpl : public ::testing::MatcherInterface<ResultType> {
+ public:
+  typedef
+      typename std::remove_reference<ResultType>::type::value_type value_type;
+
+  template <typename InnerMatcher>
+  explicit IsOkAndHoldsMatcherImpl(InnerMatcher&& inner_matcher)
+      : inner_matcher_(::testing::SafeMatcherCast<const value_type&>(
+            std::forward<InnerMatcher>(inner_matcher))) {}
+
+  void DescribeTo(std::ostream* os) const override {
+    *os << "is OK and has a value that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const override {
+    *os << "isn't OK or has a value that ";
+    inner_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(
+      ResultType actual_value,
+      ::testing::MatchResultListener* result_listener) const override {
+    if (!actual_value.ok()) {
+      *result_listener << "which has error "
+                       << static_cast<int>(GetError(actual_value));
+      return false;
+    }
+
+    // Call through to the inner matcher.
+    return inner_matcher_.MatchAndExplain(*actual_value, result_listener);
+  }
+
+ private:
+  const ::testing::Matcher<const value_type&> inner_matcher_;
+};
+
+// Implements IsOkAndHolds(m) as a polymorphic matcher.
+template <typename InnerMatcher>
+class IsOkAndHoldsMatcher {
+ public:
+  explicit IsOkAndHoldsMatcher(InnerMatcher inner_matcher)
+      : inner_matcher_(std::forward<InnerMatcher>(inner_matcher)) {}
+
+  // Converts this polymorphic matcher to a monomorphic matcher of the
+  // given type. ResultType can be either Result<T> or a
+  // reference to Result<T>.
+  template <typename ResultType>
+  operator ::testing::Matcher<ResultType>() const { // NOLINT
+    return ::testing::Matcher<ResultType>(
+        new IsOkAndHoldsMatcherImpl<const ResultType&>(inner_matcher_));
+  }
+
+ private:
+  const InnerMatcher inner_matcher_;
+};
+
+////////////////////////////////////////////////////////////
+// Implementation of IsOk().
+
+// Monomorphic implementation of matcher IsOk() for a given type T.
+// T can be Result<U>, Error, or references to either.
+template <typename T>
+class MonoIsOkMatcherImpl : public ::testing::MatcherInterface<T> {
+ public:
+  void DescribeTo(std::ostream* os) const override {
+    *os << "is OK";
+  }
+  void DescribeNegationTo(std::ostream* os) const override {
+    *os << "is not OK";
+  }
+  bool MatchAndExplain(
+      T actual_value,
+      ::testing::MatchResultListener* result_listener) const override {
+    const Error error = GetError(actual_value);
+    if (error != Error::Ok) {
+      *result_listener << "which has error " << static_cast<int>(error);
+      return false;
+    }
+    return true;
+  }
+};
+
+// Implements IsOk() as a polymorphic matcher.
+class IsOkMatcher {
+ public:
+  template <typename T>
+  operator ::testing::Matcher<T>() const { // NOLINT
+    return ::testing::Matcher<T>(new MonoIsOkMatcherImpl<const T&>());
+  }
+};
+
+////////////////////////////////////////////////////////////
+// Implementation of ErrorIs().
+
+// Monomorphic implementation of matcher ErrorIs() for a given type T.
+// T can be Result<U> or a reference to Result<U>.
+template <typename T>
+class MonoErrorIsMatcherImpl : public ::testing::MatcherInterface<T> {
+ public:
+  explicit MonoErrorIsMatcherImpl(::testing::Matcher<Error> error_matcher)
+      : error_matcher_(std::move(error_matcher)) {}
+
+  void DescribeTo(std::ostream* os) const override {
+    *os << "has an error that ";
+    error_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const override {
+    *os << "does not have an error that ";
+    error_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(
+      T actual_value,
+      ::testing::MatchResultListener* result_listener) const override {
+    Error actual_error = GetError(actual_value);
+    *result_listener << "which has error " << static_cast<int>(actual_error);
+    return error_matcher_.MatchAndExplain(actual_error, result_listener);
+  }
+
+ private:
+  const ::testing::Matcher<Error> error_matcher_;
+};
+
+// Implements ErrorIs() as a polymorphic matcher.
+template <typename ErrorMatcher>
+class ErrorIsMatcher {
+ public:
+  explicit ErrorIsMatcher(ErrorMatcher error_matcher)
+      : error_matcher_(std::forward<ErrorMatcher>(error_matcher)) {}
+
+  // Converts this polymorphic matcher to a monomorphic matcher of the
+  // given type. T can be Result<U> or a reference to Result<U>.
+  template <typename T>
+  operator ::testing::Matcher<T>() const { // NOLINT
+    return ::testing::Matcher<T>(new MonoErrorIsMatcherImpl<const T&>(
+        ::testing::MatcherCast<Error>(error_matcher_)));
+  }
+
+ private:
+  const ErrorMatcher error_matcher_;
+};
+
+} // namespace internal
+
+// Returns a gMock matcher that matches a Result<> whose error is
+// OK and whose value matches the inner matcher.
+template <typename InnerMatcherT>
+internal::IsOkAndHoldsMatcher<typename std::decay<InnerMatcherT>::type>
+IsOkAndHolds(InnerMatcherT&& inner_matcher) {
+  return internal::IsOkAndHoldsMatcher<
+      typename std::decay<InnerMatcherT>::type>(
+      std::forward<InnerMatcherT>(inner_matcher));
+}
+
+// Returns a gMock matcher that matches a Result<> whose error matches
+// the given error matcher.
+template <typename ErrorMatcherT>
+internal::ErrorIsMatcher<typename std::decay<ErrorMatcherT>::type> ErrorIs(
+    ErrorMatcherT&& error_matcher) {
+  return internal::ErrorIsMatcher<typename std::decay<ErrorMatcherT>::type>(
+      std::forward<ErrorMatcherT>(error_matcher));
+}
+
+// Returns a gMock matcher that matches a Result<> which is OK.
+inline internal::IsOkMatcher IsOk() {
+  return internal::IsOkMatcher();
+}
+
+} // namespace testing
+} // namespace runtime
+} // namespace executorch

runtime/core/testing_util/targets.bzl

@@ -0,0 +1,25 @@
+
+load("@fbsource//xplat/executorch/build:runtime_wrapper.bzl", "runtime")
+
+def define_common_targets():
+    """Defines targets that should be shared between fbcode and xplat.
+
+    The directory containing this targets.bzl file should also contain both
+    TARGETS and BUCK files that call this function.
+    """
+    runtime.cxx_library(
+        name = "error_matchers",
+        exported_headers = [
+            "error_matchers.h",
+        ],
+        visibility = [
+            "//executorch/runtime/core/testing_util/test/...",
+            "@EXECUTORCH_CLIENTS",
+        ],
+        compiler_flags = [
+            "-Wno-unneeded-internal-declaration",
+        ],
+        exported_external_deps = [
+            "gmock",
+        ],
+    )

runtime/core/testing_util/test/TARGETs

@@ -0,0 +1,8 @@
+# Any targets that should be shared between fbcode and xplat must be defined in
+# targets.bzl. This file can contain fbcode-only targets.
+
+load(":targets.bzl", "define_common_targets")
+
+oncall("executorch")
+
+define_common_targets()