Warn if the time taken by QTest::qSleep() is more than 50% off

Like this we can find out more easily if autotests fail because of
flaky timing.

Change-Id: I57b10f5fc4908bed7d00990641b2ddfd4ea84a11
Reviewed-by: Jan Arve Sæther <jan-arve.saether@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/testlib/qtestcase.cpp b/src/testlib/qtestcase.cpp
index 10bf200f4f..7b225ef5b4 100644
--- a/src/testlib/qtestcase.cpp
+++ b/src/testlib/qtestcase.cpp
@@ -2863,6 +2863,8 @@ bool QTest::currentTestFailed()
 void QTest::qSleep(int ms)
 {
     QTEST_ASSERT(ms > 0);
+    QElapsedTimer timer;
+    timer.start();
 
 #if defined(Q_OS_WINRT)
     WaitForSingleObjectEx(GetCurrentThread(), ms, true);
@@ -2872,6 +2874,15 @@ void QTest::qSleep(int ms)
     struct timespec ts = { ms / 1000, (ms % 1000) * 1000 * 1000 };
     nanosleep(&ts, NULL);
 #endif
+    // Warn if the elapsed time was more than 50% longer or more than 10% shorter than the
+    // requested time.
+    qint64 requested = 1000000 * (qint64)ms;
+    qint64 diff = timer.nsecsElapsed() - requested;
+    if (diff * 2 > requested || diff * 10 < -requested) {
+        QTestLog::warn(qPrintable(
+            QString::fromLatin1("QTest::qSleep() should have taken %1ns, but actually took %2ns!")
+                    .arg(requested).arg(diff + requested)), __FILE__, __LINE__);
+    }
 }
 
 /*! \internal