$ export QT_LOGGING_RULES="qt.text.tests.debug=true"
$ ./tst_qfontdatabase systemFixedFont               
********* Start testing of tst_QFontDatabase *********
Config: Using QtTest library 6.8.0, Qt 6.8.0 (x86_64-little_endian-lp64 shared (dynamic) debug build; by GCC 12.3.0), ubuntu 23.04
PASS   : tst_QFontDatabase::initTestCase()
QDEBUG : tst_QFontDatabase::systemFixedFont() qt.text.tests: system fixed font is QFont(monospace,11,-1,5,400,0,0,0,1,0,0,0,0,0,0,1) really fixed? false false
FAIL!  : tst_QFontDatabase::systemFixedFont() 'fdbSaysFixed' returned FALSE. ()
   Loc: [/home/liangqi/qt/qtbase/tests/auto/gui/text/qfontdatabase/tst_qfontdatabase.cpp(163)]
PASS   : tst_QFontDatabase::cleanupTestCase()
Totals: 2 passed, 1 failed, 0 skipped, 0 blacklisted, 9ms
********* Finished testing of tst_QFontDatabase *********