Adding expect<T> - a value-or-error implementation

1 files changed, 915 insertions, 0 deletions

diff --git a/tests/unit_tests/expect.cpp b/tests/unit_tests/expect.cpp
new file mode 100644
index 000000000..efa843496
--- /dev/null
+++ b/tests/unit_tests/expect.cpp
@@ -0,0 +1,915 @@
+// Copyright (c) 2018, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <gtest/gtest.h>
+
+#include <boost/algorithm/string/predicate.hpp>
+#include <boost/utility/string_ref.hpp>
+#include <string>
+#include <system_error>
+#include <type_traits>
+
+#include "common/expect.h"
+
+namespace
+{
+    struct move_only;
+    struct throw_construct;
+    struct throw_copies;
+    struct throw_moves;
+
+    struct move_only
+    {
+        move_only() = default;
+        move_only(move_only const&) = delete;
+        move_only(move_only&&) = default;
+        ~move_only() = default;
+        move_only& operator=(move_only const&) = delete;
+        move_only& operator=(move_only&&) = default;
+    };
+
+    struct throw_construct
+    {
+        throw_construct() {}
+        throw_construct(int) {}
+        throw_construct(throw_construct const&) = default;
+        throw_construct(throw_construct&&) = default;
+        ~throw_construct() = default;
+        throw_construct& operator=(throw_construct const&) = default;
+        throw_construct& operator=(throw_construct&&) = default;
+    };
+
+    struct throw_copies
+    {
+        throw_copies() noexcept {}
+        throw_copies(throw_copies const&) {}
+        throw_copies(throw_copies&&) = default;
+        ~throw_copies() = default;
+        throw_copies& operator=(throw_copies const&) { return *this; }
+        throw_copies& operator=(throw_copies&&) = default;
+        bool operator==(throw_copies const&) noexcept { return true; }
+        bool operator==(throw_moves const&) noexcept { return true; }
+    };
+
+    struct throw_moves
+    {
+        throw_moves() noexcept {}
+        throw_moves(throw_moves const&) = default;
+        throw_moves(throw_moves&&) {}
+        ~throw_moves() = default;
+        throw_moves& operator=(throw_moves const&) = default;
+        throw_moves& operator=(throw_moves&&) { return *this; }
+        bool operator==(throw_moves const&) { return true; }
+        bool operator==(throw_copies const&) { return true; }
+    };
+
+    template<typename T>
+    void construction_bench()
+    {
+        EXPECT_TRUE(std::is_copy_constructible<expect<T>>());
+        EXPECT_TRUE(std::is_move_constructible<expect<T>>());
+        EXPECT_TRUE(std::is_copy_assignable<expect<T>>());
+        EXPECT_TRUE(std::is_move_assignable<expect<T>>());
+        EXPECT_TRUE(std::is_destructible<expect<T>>());
+    }
+
+    template<typename T>
+    void noexcept_bench()
+    {
+        EXPECT_TRUE(std::is_nothrow_copy_constructible<expect<T>>());
+        EXPECT_TRUE(std::is_nothrow_move_constructible<expect<T>>());
+        EXPECT_TRUE(std::is_nothrow_copy_assignable<expect<T>>());
+        EXPECT_TRUE(std::is_nothrow_move_assignable<expect<T>>());
+        EXPECT_TRUE(std::is_nothrow_destructible<expect<T>>());
+
+        EXPECT_TRUE(noexcept(bool(std::declval<expect<T>>())));
+        EXPECT_TRUE(noexcept(std::declval<expect<T>>().has_error()));
+        EXPECT_TRUE(noexcept(std::declval<expect<T>>().error()));
+        EXPECT_TRUE(noexcept(std::declval<expect<T>>().equal(std::declval<expect<T>>())));
+        EXPECT_TRUE(noexcept(std::declval<expect<T>>() == std::declval<expect<T>>()));
+        EXPECT_TRUE(noexcept(std::declval<expect<T>>() != std::declval<expect<T>>()));
+    }
+
+    template<typename T>
+    void conversion_bench()
+    {
+        EXPECT_TRUE((std::is_convertible<std::error_code, expect<T>>()));
+        EXPECT_TRUE((std::is_convertible<std::error_code&&, expect<T>>()));
+        EXPECT_TRUE((std::is_convertible<std::error_code&, expect<T>>()));
+        EXPECT_TRUE((std::is_convertible<std::error_code const&, expect<T>>()));
+
+        EXPECT_TRUE((std::is_constructible<expect<T>, std::error_code>()));
+        EXPECT_TRUE((std::is_constructible<expect<T>, std::error_code&&>()));
+        EXPECT_TRUE((std::is_constructible<expect<T>, std::error_code&>()));
+        EXPECT_TRUE((std::is_constructible<expect<T>, std::error_code const&>()));
+    }
+}
+
+
+TEST(Expect, Constructions)
+{
+    construction_bench<void>();
+    construction_bench<int>();
+
+    EXPECT_TRUE(std::is_constructible<expect<void>>());
+
+    EXPECT_TRUE((std::is_constructible<expect<throw_construct>, expect<int>>()));
+
+    EXPECT_TRUE(std::is_move_constructible<expect<move_only>>());
+    EXPECT_TRUE(std::is_move_assignable<expect<move_only>>());
+}
+
+TEST(Expect, Conversions)
+{
+    struct implicit { implicit(int) {} };
+    struct explicit_only { explicit explicit_only(int) {} };
+
+    conversion_bench<void>();
+    conversion_bench<int>();
+
+    EXPECT_TRUE((std::is_convertible<int, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<int&&, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<int&, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<int const, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<expect<unsigned>, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<expect<unsigned>&&, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<expect<unsigned>&, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<expect<unsigned> const&, expect<int>>()));
+    EXPECT_TRUE((std::is_convertible<expect<int>, expect<implicit>>()));
+    EXPECT_TRUE((std::is_convertible<expect<int>&&, expect<implicit>>()));
+    EXPECT_TRUE((std::is_convertible<expect<int>&, expect<implicit>>()));
+    EXPECT_TRUE((std::is_convertible<expect<int> const&, expect<implicit>>()));
+    EXPECT_TRUE(!(std::is_convertible<expect<int>, expect<explicit_only>>()));
+    EXPECT_TRUE(!(std::is_convertible<expect<int>&&, expect<explicit_only>>()));
+    EXPECT_TRUE(!(std::is_convertible<expect<int>&, expect<explicit_only>>()));
+    EXPECT_TRUE(!(std::is_convertible<expect<int> const&, expect<explicit_only>>()));
+
+    EXPECT_TRUE((std::is_constructible<expect<int>, int>()));
+    EXPECT_TRUE((std::is_constructible<expect<int>, int&&>()));
+    EXPECT_TRUE((std::is_constructible<expect<int>, int&>()));
+    EXPECT_TRUE((std::is_constructible<expect<int>, int const&>()));
+    EXPECT_TRUE((std::is_constructible<expect<int>, expect<unsigned>>()));
+    EXPECT_TRUE((std::is_constructible<expect<int>, expect<unsigned>&&>()));
+    EXPECT_TRUE((std::is_constructible<expect<int>, expect<unsigned>&>()));
+    EXPECT_TRUE((std::is_constructible<expect<int>, expect<unsigned> const&>()));
+    EXPECT_TRUE((std::is_constructible<expect<implicit>, expect<int>>()));
+    EXPECT_TRUE((std::is_constructible<expect<implicit>, expect<int>&&>()));
+    EXPECT_TRUE((std::is_constructible<expect<implicit>, expect<int>&>()));
+    EXPECT_TRUE((std::is_constructible<expect<implicit>, expect<int> const&>()));
+    EXPECT_TRUE(!(std::is_constructible<expect<explicit_only>, expect<int>>()));
+    EXPECT_TRUE(!(std::is_constructible<expect<explicit_only>, expect<int>&&>()));
+    EXPECT_TRUE(!(std::is_constructible<expect<explicit_only>, expect<int>&>()));
+    EXPECT_TRUE(!(std::is_constructible<expect<explicit_only>, expect<int> const&>()));
+
+    EXPECT_EQ(expect<int>{expect<short>{100}}.value(), 100);
+
+    expect<std::string> val1{std::string{}};
+    expect<const char*> val2{"foo"};
+
+    EXPECT_EQ(val1.value(), std::string{});
+    EXPECT_EQ(val2.value(), std::string{"foo"});
+
+    const expect<std::string> val3{val2};
+
+    EXPECT_EQ(val1.value(), std::string{});
+    EXPECT_EQ(val2.value(), std::string{"foo"});
+    EXPECT_EQ(val3.value(), std::string{"foo"});
+
+    val1 = val2;
+
+    EXPECT_EQ(val1.value(), "foo");
+    EXPECT_EQ(val2.value(), std::string{"foo"});
+    EXPECT_EQ(val3.value(), "foo");
+}
+
+TEST(Expect, NoExcept)
+{
+    noexcept_bench<void>();
+    noexcept_bench<int>();
+
+    EXPECT_TRUE(std::is_nothrow_constructible<expect<void>>());
+
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<int>, int>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<int>, expect<unsigned>>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<int>, expect<unsigned>&&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<int>, expect<unsigned>&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<int>, expect<unsigned> const&>()));
+
+    EXPECT_TRUE(noexcept(expect<int>{std::declval<expect<unsigned>&&>()}));
+    EXPECT_TRUE(noexcept(expect<int>{std::declval<expect<unsigned> const&>()}));
+    EXPECT_TRUE(noexcept(std::declval<expect<int>>().has_value()));
+    EXPECT_TRUE(noexcept(*std::declval<expect<int>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<int>>().equal(std::declval<expect<unsigned>>())));
+    EXPECT_TRUE(noexcept(std::declval<expect<unsigned>>().equal(std::declval<expect<int>>())));
+    EXPECT_TRUE(noexcept(std::declval<expect<int>>().equal(0)));
+    EXPECT_TRUE(noexcept(std::declval<expect<int>>() == std::declval<expect<unsigned>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<unsigned>>() == std::declval<expect<int>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<int>>() == 0));
+    EXPECT_TRUE(noexcept(0 == std::declval<expect<int>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<int>>() != std::declval<expect<unsigned>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<unsigned>>() != std::declval<expect<int>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<int>>() != 0));
+    EXPECT_TRUE(noexcept(0 != std::declval<expect<int>>()));
+
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, std::error_code>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, std::error_code&&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, std::error_code&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, std::error_code const&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, throw_construct>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, throw_construct&&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, throw_construct&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_construct>, throw_construct const&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_construct>, expect<int>>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_construct>, expect<int>&&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_construct>, expect<int>&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_construct>, expect<int> const&>()));
+    EXPECT_TRUE(std::is_nothrow_copy_constructible<expect<throw_construct>>());
+    EXPECT_TRUE(std::is_nothrow_move_constructible<expect<throw_construct>>());
+    EXPECT_TRUE(std::is_nothrow_copy_assignable<expect<throw_construct>>());
+    EXPECT_TRUE(std::is_nothrow_move_assignable<expect<throw_construct>>());
+    EXPECT_TRUE(std::is_nothrow_destructible<expect<throw_construct>>());
+
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_copies>, std::error_code>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_copies>, std::error_code&&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_copies>, std::error_code&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_copies>, std::error_code const&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_copies>, throw_copies>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_copies>, throw_copies&&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_copies>, throw_copies&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_copies>, throw_copies const&>()));
+    EXPECT_TRUE(!std::is_nothrow_copy_constructible<expect<throw_copies>>());
+    EXPECT_TRUE(std::is_nothrow_move_constructible<expect<throw_copies>>());
+    EXPECT_TRUE(!std::is_nothrow_copy_assignable<expect<throw_copies>>());
+    EXPECT_TRUE(std::is_nothrow_move_assignable<expect<throw_copies>>());
+    EXPECT_TRUE(std::is_nothrow_destructible<expect<throw_copies>>());
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>().equal(std::declval<expect<throw_copies>>())));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>().equal(std::declval<throw_copies>())));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() == std::declval<expect<throw_copies>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() == std::declval<throw_copies>()));
+    EXPECT_TRUE(noexcept(std::declval<throw_copies>() == std::declval<expect<throw_copies>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() != std::declval<expect<throw_copies>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() != std::declval<throw_copies>()));
+    EXPECT_TRUE(noexcept(std::declval<throw_copies>() != std::declval<expect<throw_copies>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>().equal(std::declval<expect<throw_moves>>())));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>().equal(std::declval<throw_moves>())));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() == std::declval<expect<throw_moves>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() == std::declval<throw_moves>()));
+    EXPECT_TRUE(noexcept(std::declval<throw_moves>() == std::declval<expect<throw_copies>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() != std::declval<expect<throw_moves>>()));
+    EXPECT_TRUE(noexcept(std::declval<expect<throw_copies>>() != std::declval<throw_moves>()));
+    EXPECT_TRUE(noexcept(std::declval<throw_moves>() != std::declval<expect<throw_copies>>()));
+
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_moves>, std::error_code>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_moves>, std::error_code&&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_moves>, std::error_code&>()));
+    EXPECT_TRUE((std::is_nothrow_constructible<expect<throw_moves>, std::error_code const&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_moves>, throw_moves>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_moves>, throw_moves&&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_moves>, throw_moves&>()));
+    EXPECT_TRUE(!(std::is_nothrow_constructible<expect<throw_moves>, throw_moves const&>()));
+    EXPECT_TRUE(std::is_nothrow_copy_constructible<expect<throw_moves>>());
+    EXPECT_TRUE(!std::is_nothrow_move_constructible<expect<throw_moves>>());
+    EXPECT_TRUE(std::is_nothrow_copy_assignable<expect<throw_moves>>());
+    EXPECT_TRUE(!std::is_nothrow_move_assignable<expect<throw_moves>>());
+    EXPECT_TRUE(std::is_nothrow_destructible<expect<throw_copies>>());
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>().equal(std::declval<expect<throw_moves>>())));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>().equal(std::declval<throw_moves>())));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() == std::declval<expect<throw_moves>>()));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() == std::declval<throw_moves>()));
+    EXPECT_TRUE(!noexcept(std::declval<throw_moves>() == std::declval<expect<throw_moves>>()));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() != std::declval<expect<throw_moves>>()));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() != std::declval<throw_moves>()));
+    EXPECT_TRUE(!noexcept(std::declval<throw_moves>() != std::declval<expect<throw_moves>>()));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>().equal(std::declval<expect<throw_copies>>())));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>().equal(std::declval<throw_copies>())));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() == std::declval<expect<throw_copies>>()));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() == std::declval<throw_copies>()));
+    EXPECT_TRUE(!noexcept(std::declval<throw_copies>() == std::declval<expect<throw_moves>>()));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() != std::declval<expect<throw_copies>>()));
+    EXPECT_TRUE(!noexcept(std::declval<expect<throw_moves>>() != std::declval<throw_copies>()));
+    EXPECT_TRUE(!noexcept(std::declval<throw_copies>() != std::declval<expect<throw_moves>>()));
+}
+
+TEST(Expect, Trivial)
+{
+    EXPECT_TRUE(std::is_trivially_copy_constructible<expect<void>>());
+    EXPECT_TRUE(std::is_trivially_move_constructible<expect<void>>());
+    EXPECT_TRUE(std::is_trivially_destructible<expect<void>>());
+}
+
+TEST(Expect, Assignment)
+{ 
+    expect<std::string> val1{std::string{}};
+    expect<std::string> val2{"foobar"};
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_value());
+    EXPECT_TRUE(bool(val1));
+    EXPECT_TRUE(bool(val2));
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_error());
+    EXPECT_EQ(val1.value(), std::string{});
+    EXPECT_TRUE(*val1 == std::string{});
+    EXPECT_TRUE(boost::equals(val1->c_str(), ""));
+    EXPECT_TRUE(val2.value() == "foobar");
+    EXPECT_TRUE(*val2 == "foobar");
+    EXPECT_TRUE(boost::equals(val2->c_str(), "foobar"));
+    EXPECT_EQ(val1.error(), std::error_code{});
+    EXPECT_EQ(val2.error(), std::error_code{});
+    EXPECT_TRUE(!val1.equal(std::error_code{}));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+
+    val1 = std::move(val2);
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_value());
+    EXPECT_TRUE(bool(val1));
+    EXPECT_TRUE(bool(val2));
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_error());
+    EXPECT_EQ(val1.value(), "foobar");
+    EXPECT_TRUE(*val1 == "foobar");
+    EXPECT_TRUE(boost::equals(val1->c_str(), "foobar"));
+    EXPECT_EQ(val2.value(), std::string{});
+    EXPECT_TRUE(*val2 == std::string{});
+    EXPECT_TRUE(boost::equals(val2->c_str(), ""));
+    EXPECT_EQ(val1.error(), std::error_code{});
+    EXPECT_EQ(val2.error(), std::error_code{});
+    EXPECT_TRUE(!val1.equal(std::error_code{}));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+
+    val2 = val1;
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_value());
+    EXPECT_TRUE(bool(val1));
+    EXPECT_TRUE(bool(val2));
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_error());
+    EXPECT_EQ(val1.value(), "foobar");
+    EXPECT_TRUE(*val1 == "foobar");
+    EXPECT_TRUE(boost::equals(val1->c_str(), "foobar"));
+    EXPECT_EQ(val2.value(), "foobar");
+    EXPECT_TRUE(*val2 == "foobar");
+    EXPECT_TRUE(boost::equals(val2->c_str(), "foobar"));
+    EXPECT_EQ(val1.error(), std::error_code{});
+    EXPECT_EQ(val2.error(), std::error_code{});
+    EXPECT_TRUE(!val1.equal(std::error_code{}));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+
+    val1 = make_error_code(common_error::kInvalidArgument);
+
+    ASSERT_TRUE(val1.has_error());
+    ASSERT_TRUE(val2.has_value());
+    EXPECT_TRUE(!val1);
+    EXPECT_TRUE(bool(val2));
+    EXPECT_TRUE(!val1.has_value());
+    EXPECT_TRUE(!val2.has_error());
+    EXPECT_EQ(val1.error(), common_error::kInvalidArgument);
+    EXPECT_TRUE(val1 == common_error::kInvalidArgument);
+    EXPECT_TRUE(common_error::kInvalidArgument == val1);
+    EXPECT_STREQ(val2.value().c_str(), "foobar");
+    EXPECT_TRUE(*val2 == "foobar");
+    EXPECT_TRUE(boost::equals(val2->c_str(), "foobar"));
+    EXPECT_NE(val1.error(), std::error_code{});
+    EXPECT_EQ(val2.error(), std::error_code{});
+    EXPECT_TRUE(val1.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(val1.matches(std::errc::invalid_argument));
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+
+    val2 = val1;
+
+    ASSERT_TRUE(val1.has_error());
+    ASSERT_TRUE(val2.has_error());
+    EXPECT_TRUE(!val1);
+    EXPECT_TRUE(!val2);
+    EXPECT_TRUE(!val1.has_value());
+    EXPECT_TRUE(!val2.has_value());
+    EXPECT_EQ(val1.error(), common_error::kInvalidArgument);
+    EXPECT_TRUE(val1 == common_error::kInvalidArgument);
+    EXPECT_TRUE(common_error::kInvalidArgument == val1);
+    EXPECT_EQ(val2.error(), common_error::kInvalidArgument);
+    EXPECT_TRUE(val2 == common_error::kInvalidArgument);
+    EXPECT_TRUE(common_error::kInvalidArgument == val2);
+    EXPECT_NE(val1.error(), std::error_code{});
+    EXPECT_NE(val2.error(), std::error_code{});
+    EXPECT_TRUE(val1.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(val2.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(val1.matches(std::errc::invalid_argument));
+    EXPECT_TRUE(val2.matches(std::errc::invalid_argument));
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+
+    val1 = std::string{"barfoo"};
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_error());
+    EXPECT_TRUE(bool(val1));
+    EXPECT_TRUE(!val2);
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_value());
+    EXPECT_STREQ(val1.value().c_str(), "barfoo");
+    EXPECT_TRUE(*val1 == "barfoo");
+    EXPECT_TRUE(boost::equals(val1->c_str(), "barfoo"));
+    EXPECT_EQ(val2.error(), common_error::kInvalidArgument);
+    EXPECT_TRUE(val2 == common_error::kInvalidArgument);
+    EXPECT_TRUE(common_error::kInvalidArgument == val2);
+    EXPECT_EQ(val1.error(), std::error_code{});
+    EXPECT_NE(val2.error(), std::error_code{});
+    EXPECT_TRUE(!val1.equal(std::error_code{}));
+    EXPECT_TRUE(val2.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(val2.matches(std::errc::invalid_argument));
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+
+    val2 = val1;
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_value());
+    EXPECT_TRUE(bool(val1));
+    EXPECT_TRUE(bool(val2));
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_error());
+    EXPECT_EQ(val1.value(), "barfoo");
+    EXPECT_TRUE(*val1 == "barfoo");
+    EXPECT_TRUE(boost::equals(val1->c_str(), "barfoo"));
+    EXPECT_EQ(val2.value(), "barfoo");
+    EXPECT_TRUE(*val2 == "barfoo");
+    EXPECT_TRUE(boost::equals(val2->c_str(), "barfoo"));
+    EXPECT_EQ(val1.error(), std::error_code{});
+    EXPECT_EQ(val2.error(), std::error_code{});
+    EXPECT_TRUE(!val1.equal(std::error_code{}));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+}
+
+TEST(Expect, AssignmentThrowsOnMove)
+{
+    struct construct_error {};
+    struct assignment_error {};
+
+    struct throw_on_move {
+        std::string msg;
+
+        throw_on_move(const char* msg) : msg(msg) {}
+        throw_on_move(throw_on_move&&) {
+            throw construct_error{};
+        }
+        throw_on_move(throw_on_move const&) = default;
+        ~throw_on_move() = default;
+        throw_on_move& operator=(throw_on_move&&) {
+            throw assignment_error{};
+        }
+        throw_on_move& operator=(throw_on_move const&) = default;
+    };
+
+    expect<throw_on_move> val1{expect<const char*>{"foobar"}};
+    expect<throw_on_move> val2{common_error::kInvalidArgument};
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_error());
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_value());
+    EXPECT_STREQ(val1->msg.c_str(), "foobar");
+    EXPECT_EQ(val2.error(), common_error::kInvalidArgument);
+
+    EXPECT_THROW(val2 = std::move(val1), construct_error);
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_error());
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_value());
+    EXPECT_STREQ(val1->msg.c_str(), "foobar");
+    EXPECT_EQ(val2.error(), common_error::kInvalidArgument);
+
+    EXPECT_THROW(val1 = expect<const char*>{"barfoo"}, assignment_error);
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_error());
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_value());
+    EXPECT_STREQ(val1->msg.c_str(), "foobar");
+    EXPECT_EQ(val2.error(), common_error::kInvalidArgument);
+
+    EXPECT_NO_THROW(val2 = val1);
+
+    ASSERT_TRUE(val1.has_value());
+    ASSERT_TRUE(val2.has_value());
+    EXPECT_TRUE(!val1.has_error());
+    EXPECT_TRUE(!val2.has_error());
+    EXPECT_STREQ(val1->msg.c_str(), "foobar");
+    EXPECT_STREQ(val2->msg.c_str(), "foobar");
+}
+
+TEST(Expect, EqualWithStrings)
+{
+    expect<std::string> val1{std::string{}};
+    expect<std::string> val2{"barfoo"};
+    expect<boost::string_ref> val3{boost::string_ref{}};
+
+    EXPECT_TRUE(!val1.equal(val2));
+    EXPECT_TRUE(val1.equal(val3));
+    EXPECT_TRUE(!val2.equal(val1));
+    EXPECT_TRUE(!val2.equal(val3));
+    EXPECT_TRUE(val3.equal(val1));
+    EXPECT_TRUE(!val3.equal(val2));
+    EXPECT_TRUE(!(val1 == val2));
+    EXPECT_TRUE(!(val2 == val1));
+    EXPECT_TRUE(val1 == val3);
+    EXPECT_TRUE(val3 == val1);
+    EXPECT_TRUE(!(val2 == val3));
+    EXPECT_TRUE(!(val3 == val2));
+    EXPECT_TRUE(val1 != val2);
+    EXPECT_TRUE(val2 != val1);
+    EXPECT_TRUE(!(val1 != val3));
+    EXPECT_TRUE(!(val3 != val1));
+    EXPECT_TRUE(val2 != val3);
+    EXPECT_TRUE(val3 != val2);
+
+    EXPECT_TRUE(val1.equal(""));
+    EXPECT_TRUE(val2.equal("barfoo"));
+    EXPECT_TRUE(val3.equal(""));
+    EXPECT_TRUE(!val1.equal(std::error_code{}));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(!val3.equal(std::error_code{}));
+    EXPECT_TRUE(val1 == "");
+    EXPECT_TRUE("" == val1);
+    EXPECT_TRUE(val2 == "barfoo");
+    EXPECT_TRUE("barfoo" == val2);
+    EXPECT_TRUE(val3 == "");
+    EXPECT_TRUE("" == val3);
+    EXPECT_TRUE(!(val1 != ""));
+    EXPECT_TRUE(!("" != val1));
+    EXPECT_TRUE(!(val2 != "barfoo"));
+    EXPECT_TRUE(!("barfoo" != val2));
+    EXPECT_TRUE(!(val3 != ""));
+    EXPECT_TRUE(!("" != val3));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(!(val3 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val3));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+    EXPECT_TRUE(val3 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val3);
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+    EXPECT_TRUE(!val3.matches(std::error_condition{}));
+
+    val2 = make_error_code(common_error::kInvalidArgument);
+
+    EXPECT_TRUE(!val1.equal(val2));
+    EXPECT_TRUE(val1.equal(val3));
+    EXPECT_TRUE(!val2.equal(val1));
+    EXPECT_TRUE(!val2.equal(val3));
+    EXPECT_TRUE(val3.equal(val1));
+    EXPECT_TRUE(!val3.equal(val2));
+    EXPECT_TRUE(!(val1 == val2));
+    EXPECT_TRUE(!(val2 == val1));
+    EXPECT_TRUE(val1 == val3);
+    EXPECT_TRUE(val3 == val1);
+    EXPECT_TRUE(!(val2 == val3));
+    EXPECT_TRUE(!(val3 == val2));
+    EXPECT_TRUE(val1 != val2);
+    EXPECT_TRUE(val2 != val1);
+    EXPECT_TRUE(!(val1 != val3));
+    EXPECT_TRUE(!(val3 != val1));
+    EXPECT_TRUE(val2 != val3);
+    EXPECT_TRUE(val3 != val2);
+
+    EXPECT_TRUE(!val1.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(val2.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(!val3.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(val2 == common_error::kInvalidArgument);
+    EXPECT_TRUE(common_error::kInvalidArgument == val2);
+    EXPECT_TRUE(!(val2 != common_error::kInvalidArgument));
+    EXPECT_TRUE(!(common_error::kInvalidArgument != val2));
+    EXPECT_TRUE(val2.matches(std::errc::invalid_argument));
+    EXPECT_TRUE(!val2.matches(std::error_condition{}));
+
+    val1 = expect<std::string>{"barfoo"};
+
+    EXPECT_TRUE(!val1.equal(val2));
+    EXPECT_TRUE(!val1.equal(val3));
+    EXPECT_TRUE(!val2.equal(val1));
+    EXPECT_TRUE(!val2.equal(val3));
+    EXPECT_TRUE(!val3.equal(val1));
+    EXPECT_TRUE(!val3.equal(val2));
+    EXPECT_TRUE(!(val1 == val2));
+    EXPECT_TRUE(!(val2 == val1));
+    EXPECT_TRUE(!(val1 == val3));
+    EXPECT_TRUE(!(val3 == val1));
+    EXPECT_TRUE(!(val2 == val3));
+    EXPECT_TRUE(!(val3 == val2));
+    EXPECT_TRUE(val1 != val2);
+    EXPECT_TRUE(val2 != val1);
+    EXPECT_TRUE(val1 != val3);
+    EXPECT_TRUE(val3 != val1);
+    EXPECT_TRUE(val2 != val3);
+    EXPECT_TRUE(val3 != val2);
+
+    EXPECT_TRUE(val1.equal("barfoo"));
+    EXPECT_TRUE(val1 == "barfoo");
+    EXPECT_TRUE("barfoo" == val1);
+    EXPECT_TRUE(!(val1 != "barfoo"));
+    EXPECT_TRUE(!("barfoo" != val1));
+    EXPECT_TRUE(!val1.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(!(val1 == common_error::kInvalidArgument));
+    EXPECT_TRUE(!(common_error::kInvalidArgument == val1));
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!val1.matches(std::error_condition{}));
+    EXPECT_TRUE(!val1.matches(std::errc::invalid_argument));
+}
+
+TEST(Expect, EqualWithVoid)
+{
+    const expect<void> val1;
+    expect<void> val2;
+
+    EXPECT_TRUE(val1.equal(val2));
+    EXPECT_TRUE(val2.equal(val1));
+    EXPECT_TRUE(!val1.equal(std::error_code{}));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(val1 == val2);
+    EXPECT_TRUE(val2 == val1);
+    EXPECT_TRUE(!(val1 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val1));
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(!(val1 != val2));
+    EXPECT_TRUE(!(val2 != val1));
+    EXPECT_TRUE(val1 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val1);
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+
+    val2 = make_error_code(common_error::kInvalidArgument);
+
+    EXPECT_TRUE(!val1.equal(val2));
+    EXPECT_TRUE(!val2.equal(val1));
+    EXPECT_TRUE(!val1.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(val2.equal(common_error::kInvalidArgument));
+    EXPECT_TRUE(!val2.equal(std::error_code{}));
+    EXPECT_TRUE(!(val1 == val2));
+    EXPECT_TRUE(!(val2 == val1));
+    EXPECT_TRUE(val2 == common_error::kInvalidArgument);
+    EXPECT_TRUE(common_error::kInvalidArgument == val2);
+    EXPECT_TRUE(!(val2 == std::error_code{}));
+    EXPECT_TRUE(!(std::error_code{} == val2));
+    EXPECT_TRUE(val1 != val2);
+    EXPECT_TRUE(val2 != val1);
+    EXPECT_TRUE(!(val2 != common_error::kInvalidArgument));
+    EXPECT_TRUE(!(common_error::kInvalidArgument != val2));
+    EXPECT_TRUE(val2 != std::error_code{});
+    EXPECT_TRUE(std::error_code{} != val2);
+}
+
+TEST(Expect, EqualNoCopies)
+{
+    struct copy_error {};
+
+    struct throw_on_copy {
+        throw_on_copy() = default;
+        throw_on_copy(int) noexcept {}
+        throw_on_copy(throw_on_copy const&) {
+            throw copy_error{};
+        }
+        ~throw_on_copy() = default;
+        throw_on_copy& operator=(throw_on_copy const&) {
+            throw copy_error{};
+        }
+
+        bool operator==(throw_on_copy const&) const noexcept { return true; }
+    };
+
+    expect<throw_on_copy> val1{expect<int>{0}};
+    expect<throw_on_copy> val2{expect<int>{0}};
+
+    EXPECT_TRUE(val1.equal(val2));
+    EXPECT_TRUE(val2.equal(val1));
+    EXPECT_TRUE(val1 == val2);
+    EXPECT_TRUE(val2 == val1);
+    EXPECT_TRUE(!(val1 != val2));
+    EXPECT_TRUE(!(val2 != val1));
+
+    EXPECT_TRUE(val1.equal(throw_on_copy{}));
+    EXPECT_TRUE(val1 == throw_on_copy{});
+    EXPECT_TRUE(throw_on_copy{} == val1);
+    EXPECT_TRUE(!(val1 != throw_on_copy{}));
+    EXPECT_TRUE(!(throw_on_copy{} != val1));
+
+    throw_on_copy val3;
+
+    EXPECT_TRUE(val1.equal(val3));
+    EXPECT_TRUE(val1 == val3);
+    EXPECT_TRUE(val3 == val1);
+    EXPECT_TRUE(!(val1 != val3));
+    EXPECT_TRUE(!(val3 != val1));
+
+    expect<throw_on_copy> val4{common_error::kInvalidArgument};
+
+    EXPECT_TRUE(!val4.equal(throw_on_copy{}));
+    EXPECT_TRUE(!(val4 == throw_on_copy{}));
+    EXPECT_TRUE(!(throw_on_copy{} == val4));
+    EXPECT_TRUE(val4 != throw_on_copy{});
+    EXPECT_TRUE(throw_on_copy{} != val4);
+    EXPECT_TRUE(!val4.equal(val3));
+    EXPECT_TRUE(!(val4 == val3));
+    EXPECT_TRUE(!(val3 == val4));
+    EXPECT_TRUE(val4 != val3);
+    EXPECT_TRUE(val3 != val4);
+}
+
+TEST(Expect, Macros) {
+    EXPECT_TRUE(
+        [] () -> ::common_error {
+            MONERO_PRECOND(true);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidErrorCode
+    );
+    EXPECT_TRUE(
+        [] () -> ::common_error {
+            MONERO_PRECOND(false);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidArgument
+    );
+    EXPECT_TRUE(
+        [] () -> std::error_code {
+            MONERO_PRECOND(true);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidErrorCode
+    );
+    EXPECT_TRUE(
+        [] () -> std::error_code {
+            MONERO_PRECOND(false);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidArgument
+    );
+    EXPECT_TRUE(
+        [] () -> expect<void> {
+            MONERO_PRECOND(true);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidErrorCode
+    );
+    EXPECT_TRUE(
+        [] () -> expect<void> {
+            MONERO_PRECOND(false);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidArgument
+    );
+    EXPECT_TRUE(
+        [] () -> expect<int> {
+            MONERO_PRECOND(true);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidErrorCode
+    );
+    EXPECT_TRUE(
+        [] () -> expect<int> {
+            MONERO_PRECOND(false);
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidArgument
+    );
+
+    EXPECT_TRUE(
+        [] () -> std::error_code {
+            MONERO_CHECK(expect<void>{});
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidErrorCode
+    );
+    EXPECT_TRUE(
+        [] () -> std::error_code {
+            MONERO_CHECK(expect<void>{common_error::kInvalidArgument});
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidArgument
+    );
+    EXPECT_TRUE(
+        [] () -> expect<void> {
+            MONERO_CHECK(expect<void>{});
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidErrorCode
+    );
+    EXPECT_TRUE(
+        [] () -> expect<void> {
+            MONERO_CHECK(expect<void>{common_error::kInvalidArgument});
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidArgument
+    );
+    EXPECT_TRUE(
+        [] () -> expect<int> {
+            MONERO_CHECK(expect<void>{});
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidErrorCode
+    );
+    EXPECT_TRUE(
+        [] () -> expect<int> {
+            MONERO_CHECK(expect<void>{common_error::kInvalidArgument});
+            return {common_error::kInvalidErrorCode};
+        } () == common_error::kInvalidArgument
+    );
+
+    EXPECT_NO_THROW(MONERO_UNWRAP(success()));
+    EXPECT_NO_THROW(MONERO_UNWRAP(expect<void>{}));
+    EXPECT_NO_THROW(MONERO_UNWRAP(expect<int>{0}));
+    EXPECT_THROW(
+        MONERO_UNWRAP(expect<void>{common_error::kInvalidArgument}), std::system_error
+    );
+    EXPECT_THROW(
+        MONERO_UNWRAP(expect<int>{common_error::kInvalidArgument}), std::system_error
+    );
+}
+