tst_QDateTimeEdit: correct computation of width of gap

Although the zone's daylight time offset is usually the width of the
gap, it's possible the transition is (or includes) a change to
standard time; so determine the actual gap width by comparing the
difference between time a day earlier and later to the usual duration
of two days. Also skip the test if the transition isn't really a gap.

Change-Id: I56e381c9f74cfa1806d43b3ed5e4637436ebdf57
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 28c6868611fda392bd2ab9b5b509466c4e23ddd7)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/tests/auto/widgets/widgets/qdatetimeedit/tst_qdatetimeedit.cpp b/tests/auto/widgets/widgets/qdatetimeedit/tst_qdatetimeedit.cpp
index 13a47e53b1..940909567e 100644
--- a/tests/auto/widgets/widgets/qdatetimeedit/tst_qdatetimeedit.cpp
+++ b/tests/auto/widgets/widgets/qdatetimeedit/tst_qdatetimeedit.cpp
@@ -4575,6 +4575,13 @@ static QDateTime findSpring(int year, const QTimeZone &timeZone)
 
     return spring;
 };
+
+// Number of missing seconds between a day before and a day after when.
+// If when is the time of a spring-forward transition, this is the width of its gap.
+static int missingSecondsNear(const QDateTime &when)
+{
+    return 2 * 24 * 60 * 60 - when.addDays(-1).secsTo(when.addDays(1));
+}
 #endif
 
 /*!
@@ -4598,7 +4605,10 @@ void tst_QDateTimeEdit::springForward_data()
         QSKIP("Failed to obtain valid spring forward datetime for 2019!");
 
     const QDate springDate = springTransition.date();
-    const int gapWidth = timeZone.daylightTimeOffset(springTransition.addDays(1));
+    const int gapWidth = missingSecondsNear(springTransition);
+    if (gapWidth <= 0)
+        QSKIP("Spring forward transition did not actually skip any time!");
+
     const QTime springGap = springTransition.time().addSecs(-gapWidth);
     const QTime springGapMiddle = springTransition.time().addSecs(-gapWidth / 2);
     const QByteArray startGapTime = springGap.toString("hh:mm").toLocal8Bit();
@@ -4696,7 +4706,10 @@ void tst_QDateTimeEdit::stepIntoDSTGap_data()
         QSKIP("Failed to obtain valid spring forward datetime for 2007!");
 
     const QDate spring = springTransition.date();
-    const int gapWidth = timeZone.daylightTimeOffset(springTransition.addDays(1));
+    const int gapWidth = missingSecondsNear(springTransition);
+    if (gapWidth <= 0)
+        QSKIP("Spring forward transition did not actually skip any time!");
+
     const QTime springGap = springTransition.time().addSecs(-gapWidth);
     const QByteArray springTime = springGap.toString("hh:mm").toLocal8Bit();