Try again to make QDeadlineTimer test robust against context switches

Instead of comparing to absolute values, compare the result from
QDeadlineTimer with the reference clock types from std::chrono. Pass
the test as long as we are within 10% of that reference.

In addition, handle the case where QTest::qSleep sleeps for more than
10% longer or shorter than what is requested, and if so, abort the
test.

Change-Id: If8b77aea55a8c5c53e96427b2fff2f78281d0f82
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 34 insertions, 16 deletions

diff --git a/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp b/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
index 35c5e7cb75..db53c3f20c 100644
--- a/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
+++ b/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
@@ -573,12 +573,32 @@ void tst_QDeadlineTimer::stdchrono()
 
     QCOMPARE(deadline.remainingTimeAsDuration(), nanoseconds::zero());
 
+    /*
+        Call QTest::qSleep, and return true if the time actually slept is
+        within \a deviationPercent percent of the requested sleep time.
+        Otherwise, return false, in which case the test should to abort.
+    */
+    auto sleepHelper = [](int ms, int deviationPercent = 10) -> bool {
+        auto before = steady_clock::now();
+        QTest::qSleep(ms);
+        auto after = steady_clock::now();
+        auto diff = duration_cast<milliseconds>(after - before).count();
+        bool inRange = qAbs(diff - ms) < ms * deviationPercent/100.0;
+        if (!inRange)
+            qWarning() << "sleeping" << diff << "instead of" << ms << inRange;
+        return inRange;
+    };
+
     auto steady_before = steady_clock::now();
     auto system_before = system_clock::now();
 
-    QTest::qSleep(minResolution);
+    if (!sleepHelper(minResolution))
+        QSKIP("Slept too long");
     auto now = QDeadlineTimer::current(timerType);
-    QTest::qSleep(minResolution);
+    auto steady_reference = steady_clock::now();
+    auto system_reference = system_clock::now();
+    if (!sleepHelper(minResolution))
+        QSKIP("Slept too long");
 
     auto sampling_start = steady_clock::now();
     auto steady_deadline = now.deadline<steady_clock>();
@@ -599,35 +619,33 @@ void tst_QDeadlineTimer::stdchrono()
     }
 
     {
-        auto diff = duration_cast<milliseconds>(steady_after - steady_deadline);
-        QVERIFY2(diff.count() > minResolution/2, QByteArray::number(qint64(diff.count())));
-        QVERIFY2(diff.count() < 3*minResolution/2, QByteArray::number(qint64(diff.count())));
+        auto reference = duration_cast<milliseconds>(steady_after - steady_reference).count();
+        auto diff = duration_cast<milliseconds>(steady_after - steady_deadline).count();
+        QVERIFY2(diff > reference * 0.9 && diff < reference*1.1, QByteArray::number(qint64(diff)));
         QDeadlineTimer dt_after(steady_after, timerType);
         QVERIFY2(now < dt_after,
                  ("now = " + QLocale().toString(now.deadlineNSecs()) +
                  "; after = " + QLocale().toString(dt_after.deadlineNSecs())).toLatin1());
 
-        diff = duration_cast<milliseconds>(steady_deadline - steady_before);
-        QVERIFY2(diff.count() > minResolution/2, QByteArray::number(qint64(diff.count())));
-        QVERIFY2(diff.count() < 3*minResolution/2, QByteArray::number(qint64(diff.count())));
+        reference = duration_cast<milliseconds>(steady_reference - steady_before).count();
+        diff = duration_cast<milliseconds>(steady_deadline - steady_before).count();
+        QVERIFY2(diff > reference * 0.9 && diff < reference*1.1, QByteArray::number(qint64(diff)));
         QDeadlineTimer dt_before(steady_before, timerType);
         QVERIFY2(now > dt_before,
                  ("now = " + QLocale().toString(now.deadlineNSecs()) +
                  "; before = " + QLocale().toString(dt_before.deadlineNSecs())).toLatin1());
     }
     {
-        auto diff = duration_cast<milliseconds>(system_after - system_deadline);
-        QVERIFY2(diff.count() > minResolution/2, QByteArray::number(qint64(diff.count())));
-        QVERIFY2(diff.count() < 3*minResolution/2, QByteArray::number(qint64(diff.count())));
-        QDeadlineTimer dt_after(system_after, timerType);
+        auto reference = duration_cast<milliseconds>(system_after - system_reference).count();
+        auto diff = duration_cast<milliseconds>(system_after - system_deadline).count();
+        QVERIFY2(diff > reference * 0.9 && diff < reference*1.1, QByteArray::number(qint64(diff)));        QDeadlineTimer dt_after(system_after, timerType);
         QVERIFY2(now < dt_after,
                  ("now = " + QLocale().toString(now.deadlineNSecs()) +
                  "; after = " + QLocale().toString(dt_after.deadlineNSecs())).toLatin1());
 
-        diff = duration_cast<milliseconds>(system_deadline - system_before);
-        QVERIFY2(diff.count() > minResolution/2, QByteArray::number(qint64(diff.count())));
-        QVERIFY2(diff.count() < 3*minResolution/2, QByteArray::number(qint64(diff.count())));
-        QDeadlineTimer dt_before(system_before, timerType);
+        reference = duration_cast<milliseconds>(system_reference - system_before).count();
+        diff = duration_cast<milliseconds>(steady_deadline - steady_before).count();
+        QVERIFY2(diff > reference * 0.9 && diff < reference*1.1, QByteArray::number(qint64(diff)));        QDeadlineTimer dt_before(system_before, timerType);
         QVERIFY2(now > dt_before,
                  ("now = " + QLocale().toString(now.deadlineNSecs()) +
                  "; before = " + QLocale().toString(dt_before.deadlineNSecs())).toLatin1());