Use QFINDTESTDATA, which can find files easily

src/libdanbooru/autotests/CMakeLists.txt

@@ -6,5 +6,3 @@ ecm_add_test(test_danbooru_post.cpp LINK_LIBRARIES
              Qt5::Core
              danbooru
              TEST_NAME test_danbooru_post)
-
-configure_file(konachan.json konachan.json COPYONLY)

src/libdanbooru/autotests/test_danbooru_post.h

@@ -31,7 +31,7 @@ class TestDanbooruPost: public QObject
 Q_OBJECT
 
 private:
-    QLatin1String m_fileName = QLatin1String("konachan.json");
+    QString m_fileName = QFINDTESTDATA("konachan.json");
     Danbooru::DanbooruPost* m_post = nullptr;
     QVariantMap m_data;