kdescendantsproxymodel_smoketest started failing between 5.74.0 and 5.75.0, probably with  24c7bd8cb0640770d41165fca253b83e58bd8cc9.
Same on build.kde.org (https://build.kde.org/job/Frameworks/job/kitemmodels/job/kf5-qt5%20SUSEQt5.15/26/console)

STEPS TO REPRODUCE
1. cmake && make && make test

OBSERVED RESULT
3: Test command: /var/tmp/paludis/build/kde-frameworks-kitemmodels-5.75.0/work/build/bin/kdescendantsproxymodel_smoketest
3: Environment variables: 
3:  QT_PLUGIN_PATH=/var/tmp/paludis/build/kde-frameworks-kitemmodels-5.75.0/work/build/bin:/usr/host/lib/qt6/plugins
3: Test timeout computed to be: 10000000
make: *** No rule to make target 'check'.  Stop.
make -j14 ARGS=--verbose test
3: QStandardPaths: wrong permissions on runtime directory /var/tmp/paludis/build/kde-frameworks-kitemmodels-5.75.0/temp/, 7755 instead of 7700
3: QStandardPaths: wrong permissions on runtime directory /var/tmp/paludis/build/kde-frameworks-kitemmodels-5.75.0/temp/, 7755 instead of 7700
3: QStandardPaths: wrong permissions on runtime directory /var/tmp/paludis/build/kde-frameworks-kitemmodels-5.75.0/temp/, 7755 instead of 7700
3: ********* Start testing of DescendantsProxyModelTest *********
3: Config: Using QtTest library 5.15.1, Qt 5.15.1 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 10.2.0)
3: PASS   : DescendantsProxyModelTest::initTestCase()
3: PASS   : DescendantsProxyModelTest::testEmptyModel()
3: PASS   : DescendantsProxyModelTest::testSourceReset()
3: PASS   : DescendantsProxyModelTest::testDestroyModel()
3: FAIL!  : DescendantsProxyModelTest::testInsertWhenEmpty(insert01) Compared values are not the same
3:    Actual   (result.takeAt(0).toInt()): 7
3:    Expected (signalType)              : 1
3:    Loc: [/var/tmp/paludis/build/kde-frameworks-kitemmodels-5.75.0/work/kitemmodels-5.75.0/autotests/proxymodeltestsuite/proxymodeltest.cpp(190)]
3: munmap_chunk(): invalid pointer
 3/15 Test  #3: kdescendantsproxymodel_smoketest ...Child aborted***Exception:   0.10 sec

EXPECTED RESULT
test passes


SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.20.0
KDE Frameworks Version: 5.75.0
Qt Version: 5.15.1