feat utest: introduce LoggingFixture

core/utest/include/userver/utest/logging_fixture.hpp

@@ -0,0 +1,80 @@
+#pragma once
+
+#include <userver/utest/utest.hpp>
+#include <userver/logging/log.hpp>
+#include <userver/logging/null_logger.hpp>
+#include <userver/logging/impl/logger_base.hpp>
+
+#include <atomic>
+#include <concepts>
+#include <iostream>
+#include <mutex>
+#include <string_view>
+#include <thread>
+
+USERVER_NAMESPACE_BEGIN
+
+namespace utest {
+
+namespace detail {
+
+class CoutLogger final : public logging::impl::TextLogger {
+public:
+    CoutLogger() : TextLogger(logging::Format::kTskv)
+    {
+        SetLevel(logging::GetDefaultLoggerLevel()); // consider gtest_hooks.hpp usage
+    }
+
+    void Log(logging::Level level, logging::impl::formatters::LoggerItemRef item) override
+    {
+        UASSERT(dynamic_cast<logging::impl::TextLogItem*>(&item));
+        auto& str = static_cast<logging::impl::TextLogItem&>(item);
+        std::lock_guard lock(m_mutex);
+        std::cout << std::this_thread::get_id()
+            << "\t" << logging::ToString(level) 
+            << "\t" << std::string_view(str.log_line.begin(), str.log_line.end())
+            << std::endl;
+    }
+private:
+    std::mutex m_mutex;
+};
+
+class LoggingFixtureEnvironment
+{
+    CoutLogger m_logger;
+
+    static auto& NonOwningNullLogger() noexcept
+    {
+        static std::atomic<logging::impl::LoggerBase*> nullLoggerPtr(&logging::GetNullLogger());
+	return nullLoggerPtr;
+    }
+
+public:
+    LoggingFixtureEnvironment()
+    {
+        logging::impl::SetDefaultLoggerRef(m_logger); 
+    }
+
+    ~LoggingFixtureEnvironment()
+    {
+        logging::impl::SetDefaultLoggerRef(*NonOwningNullLogger());
+    }
+};
+
+}  // namespace detail
+
+/// @ingroup userver_utest
+///
+/// @brief Fixture for logger usage due to unit tests
+struct LoggingFixture : ::testing::Test, detail::LoggingFixtureEnvironment {};
+
+template<typename DerivedEnvironment>
+struct LoggingFixtureEx : ::testing::Test, DerivedEnvironment
+{
+    static_assert(std::derived_from<DerivedEnvironment, detail::LoggingFixtureEnvironment>);
+};
+
+}  // namespace utest
+
+USERVER_NAMESPACE_END
+

core/utest/src/utest/logging_fixture_test.cpp

@@ -0,0 +1,21 @@
+#include <userver/utest/logging_fixture.hpp>
+#include <userver/utest/utest.hpp>
+
+USERVER_NAMESPACE_BEGIN
+
+namespace utest
+{
+
+UTEST_F(LoggingFixture, DebugMessage)
+{
+    LOG_DEBUG() << "Test message";
+}
+
+UTEST_F(LoggingFixture, InfoMessage)
+{
+    LOG_INFO() << "Test message";
+}
+
+} // namespace utest
+
+USERVER_NAMESPACE_END