Add some tests for 'stout::expected'

Author: ArthurBandaryk

include/stout/expected.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "tl/expected.hpp"
+
+////////////////////////////////////////////////////////////////////////
+
+namespace stout {
+
+////////////////////////////////////////////////////////////////////////
+
+template <typename T, typename Error = std::string>
+using expected = tl::expected<T, Error>;
+
+template <typename Error = std::string>
+using unexpected = tl::unexpected<Error>;
+
+using tl::make_unexpected;
+
+////////////////////////////////////////////////////////////////////////
+
+} // namespace stout
+
+////////////////////////////////////////////////////////////////////////

tests/BUILD.bazel

@@ -39,6 +39,7 @@ cc_test(
 cc_test(
     name = "stout",
     srcs = [
+        "expected_tests.cc",
         "stringify_tests.cc",
         "temporary_directory_test_tests.cc",
     ],

tests/expected_tests.cc

@@ -0,0 +1,33 @@
+#include "gtest/gtest.h"
+#include "stout/expected.h"
+
+stout::expected<int, std::string> divide(int divident, int divider) {
+  if (!divider) {
+    return stout::unexpected<std::string>{"divide by zero"};
+  } else {
+    return divident / divider;
+  }
+}
+
+TEST(Expected, SucceedResult) {
+  const auto result = divide(6, 3);
+
+  EXPECT_TRUE(result.has_value());
+  EXPECT_EQ(2, *result);
+}
+
+TEST(Expected, DivideByZero) {
+  const auto result = divide(6, 0);
+
+  EXPECT_TRUE(!result.has_value());
+  EXPECT_EQ("divide by zero", result.error());
+}
+
+TEST(Expected, MakeUnexpected) {
+  auto error = []() {
+    return stout::make_unexpected<std::string>("error");
+  };
+  const auto result = error();
+
+  EXPECT_EQ("error", result.value());
+}