Detecting custom testers takes a lot of time

[mstahv]

Executing similar simple test with Karibu is thus ~ 50% faster.

Testable with https://github.com/mstahv/calc-ui-unit-testing :

• Import to IDE
• Execute test class separately: Karibu ~ 500ms, TestBench ~ 1200ms

Probably should either cache the lookup somehow or utilize e.g. Jandex indexing.

CC: @mcollovati @caalador, discussed on Friday.

[mcollovati]

Could also be route scanning. Can you try to use ViewPackages annotation on the test class to see if bootstrap time decreases?

Looking at the code it seems like the tester scanning is limited to Vaadin packages, but route scan by default has no restrictions

[mstahv]

Roughly ~ 700ms with that (@ViewPackages(packages = "org.example")).

[mcollovati]

Currently to find testers we perform a classpath scan.
I wonder if we can, at least for out-of-the-box implementations, use ServiceLoader. This would need the introduction of an additional interface ComponentTesterProvider because ServiceLoader mechanism requires that loaded classes provide a public no-args constructor.
I'm not sure if this approach could be faster or not, but it might be worth trying.

Something like the following:

interface ComponentTesterProvider {
    Set<Class<? extend ComponentTester> testers();
}

[mcollovati]

Anyway, most of the bootstrap time is because of view scanning; searching for tester seems quite fast, since it is limited to com.vaadin.flow.component packages.