chore: Add unit tests for DocumentContextReader (#90)

chore: Add unit tests for DocumentContextReader

The tests are based on GTest like some tests in Qt Creator itself, which
makes it easy to run as full Qt Creator does not need to be started.

test/unittest_main.cpp

@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2025 Povilas Kanapickas
+ *
+ * This file is part of QodeAssist.
+ *
+ * QodeAssist is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * QodeAssist is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with QodeAssist. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <gtest/gtest.h>
+#include <QGuiApplication>
+
+int main(int argc, char *argv[])
+{
+    QGuiApplication application(argc, argv);
+    testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}