Implement logging abstraction (#371)

Fixes #290

unittests/util/Fixtures.h

@@ -0,0 +1,93 @@
+#ifndef CLIO_UNITTEST_FIXTURES_H
+#define CLIO_UNITTEST_FIXTURES_H
+
+#include <ios>
+#include <mutex>
+
+#include <gtest/gtest.h>
+#include <log/Logger.h>
+
+/**
+ * @brief Fixture with LogService support.
+ */
+class LoggerFixture : public ::testing::Test
+{
+    /**
+     * @brief A simple string buffer that can be used to mock std::cout for
+     * console logging.
+     */
+    class FakeBuffer final : public std::stringbuf
+    {
+    public:
+        std::string
+        getStrAndReset()
+        {
+            auto value = str();
+            str("");
+            return value;
+        }
+    };
+
+    FakeBuffer buffer_;
+    std::ostream stream_ = std::ostream{&buffer_};
+
+protected:
+    // Simulates the `LogService::init(config)` call
+    void
+    SetUp() override
+    {
+        static std::once_flag once_;
+        std::call_once(once_, [] {
+            boost::log::add_common_attributes();
+            boost::log::register_simple_formatter_factory<clio::Severity, char>(
+                "Severity");
+        });
+
+        namespace src = boost::log::sources;
+        namespace keywords = boost::log::keywords;
+        namespace sinks = boost::log::sinks;
+        namespace expr = boost::log::expressions;
+        auto core = boost::log::core::get();
+
+        core->remove_all_sinks();
+        boost::log::add_console_log(
+            stream_, keywords::format = "%Channel%:%Severity% %Message%");
+        auto min_severity = expr::channel_severity_filter(
+            clio::log_channel, clio::log_severity);
+        min_severity["General"] = clio::Severity::DEBUG;
+        min_severity["Trace"] = clio::Severity::TRACE;
+        core->set_filter(min_severity);
+        core->set_logging_enabled(true);
+    }
+
+    void
+    checkEqual(std::string expected)
+    {
+        auto value = buffer_.getStrAndReset();
+        ASSERT_EQ(value, expected + '\n');
+    }
+
+    void
+    checkEmpty()
+    {
+        ASSERT_TRUE(buffer_.getStrAndReset().empty());
+    }
+};
+
+/**
+ * @brief Fixture with LogService support but completely disabled logging.
+ *
+ * This is meant to be used as a base for other fixtures.
+ */
+class NoLoggerFixture : public LoggerFixture
+{
+protected:
+    void
+    SetUp() override
+    {
+        LoggerFixture::SetUp();
+        boost::log::core::get()->set_logging_enabled(false);
+    }
+};
+
+#endif  // CLIO_UNITTEST_FIXTURES_H