RFR: 8359598: [TestBug] VirtualFlowTestUtils should not create a temporary Stage

[Marius Hanl]

On Mon, 16 Jun 2025 17:44:48 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> Currently, the VirtualFlowTestUtils used ONLY for tests has many utility methods to get and do something with the VirtualFlow of Virtualized Controls.
>> 
>> It has one flaw: It may creates a temporary Stage with the StageLoader, when the Control was never inside a Scene (and Stage) yet. This is done to get the VirtualFlow, which is not possible otherwise.
>> 
>> Take the following test code:
>> 
>> VirtualFlowTestUtils.clickOnRow(tableView, 2);
>> VirtualFlowTestUtils.clickOnRow(tableView, 4);
>> 
>> 
>> What it does it to create a Stage for the first method and dispose it after. And create another Stage for the second method and dispose it after.
>> 
>> This does not test a realistic scenario and the chance is quite high that developers used that methods without even knowing that it contains such logic.
>> 
>> So the idea is to remove the StageLoader code from VirtualFlowTestUtils and rather use it in the Test code before calling the Util methods.
>> 
>> For the example above, this would result in:
>> 
>> stageLoader = new StageLoader(tableView);
>> VirtualFlowTestUtils.clickOnRow(tableView, 2);
>> VirtualFlowTestUtils.clickOnRow(tableView, 4);
>> 
>> 
>> The stageLoader should be disposed in an @AfterEach.
>> 
>> Note: Nearly all touched tests are indeed much older test code. New tests are not affected and already use it correcty.
>> Sometimes a call to `Toolkit.getToolkit().firePulse();` was needed. Previously, creating a new Stage for every call to the util methods did that implicitly.
>
> modules/javafx.controls/src/test/java/test/com/sun/javafx/scene/control/infrastructure/VirtualFlowTestUtils.java line 349:
> 
>> 347:         flow = (VirtualFlow<?>)control.lookup("#virtual-flow");
>> 348: 
>> 349:         if (sl != null) {
> 
> should we have a check here with a helpful message (which recommends to use `StageLoader`), instead of returning `null`?

I thought about this as well. No strong opinion from my side.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1829#discussion_r2154281361