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Item7826: The HASHREVERSE test case in SpreadSheetPluginTestCases fails.... randomly

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AppliesTo: Component: Priority: CurrentState: WaitingFor: TargetRelease ReleasedIn
Extension SpreadSheetPlugin Low Closed TWiki:Main.HaraldJoerg minor 6.1.0

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For the semi-automatic test for SpreadSheetPlugin, the tests are shipped as an extra topic SpreadSheetPluginTestCases. Every now and then the test for $HASHREVERSE fails like this:

<ul> <li> $SETHASH()=|| </li> <li> $LIST2HASH(age, Jane, 26, Tim, 27, Sam, 27)=|| </li> <li> $HASHREVERSE(age)=|| </li> <li>
$HASH2LIST(age, $key: $value)=|26: Jane, 27: Tim|
$HASH2LIST(age, $key: $value)=|26: Jane, 27: Sam|
</li> <li> $HASHREVERSE(height)=|| </li> <li> $HASH2LIST(height)=|| </li> <li> $HASHREVERSE()=|| </li> </ul>

Root cause: Since Perl 5.18, Perl randomizes the order of keys in a hash. The two hash entries for Tim and Sam both share a value of 27. On flipping the hash over, it has always been known and expected behavior that only one of the two can survive under the key of 27 in the reversed hash. But as of today, we can't know which one.

Fix: Pretend that Sam had his birthday yesterday and make him 28 years old. This should to be changed in the plugin docs, too, though the warning " Hash keys are always unique, e.g. multiple identical values will be reduced to one key." should be kept in place.

Side note: The function $HASH2LIST sorts the keys of the hash before converting to a list and is therefore not affected by the randomization.

-- TWiki:Main/HaraldJoerg - 2017-10-20

Summary The HASHREVERSE test case in SpreadSheetPluginTestCases fails.... randomly
ReportedBy TWiki:Main.HaraldJoerg
Codebase ~twiki4, 6.0.2
SVN Range TWiki-6.0.2-trunk, Thu, 17 Aug 2017, build 30373
AppliesTo Extension
Component SpreadSheetPlugin
Priority Low
CurrentState Closed
WaitingFor TWiki:Main.HaraldJoerg
Checkins TWikirev:30400
TargetRelease minor
ReleasedIn 6.1.0
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Topic revision: r4 - 2018-07-17 - PeterThoeny
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