feat(tests): rework tests in numerous ways (#3059)

tests/tests_environment.h

@@ -0,0 +1,22 @@
+/**
+ * @file tests/tests_environment.h
+ * @brief Declarations for SunshineEnvironment.
+ */
+#pragma once
+#include "tests_common.h"
+
+struct SunshineEnvironment: testing::Environment {
+  void
+  SetUp() override {
+    mail::man = std::make_shared<safe::mail_raw_t>();
+    deinit_log = logging::init(0, "test_sunshine.log");
+  }
+
+  void
+  TearDown() override {
+    deinit_log = {};
+    mail::man = {};
+  }
+
+  std::unique_ptr<logging::deinit_t> deinit_log;
+};