Docs. Troubleshooting test run configuration with Java 17

[alisevych]

Description

Add Troubleshooting section in User guide on how to run tests with Java 17 using reflection.
In order to support user with bug

• UtUtils methods using setAccessible doesn't work in Java 17 #2026

Please consider the best place for Troubleshooting section.

Expected behavior

UnitTestBot sometimes cannot combine Object assemble model without using reflection.
Sometimes a private field needs to be set or got.
Reflection methods using setAccessible is forbidden in Java 17+.
User can add keys to the JVm in order to run the tests.
Otherwise UtUtils methods can fail.

Environment

IntelliJ IDEA Ultimate 2023.3.*

Potential alternatives

Possibility to add needed keys automatically can be very complex.
One can see the list of keys needed to run tests for UnitTestBot: build.gradle.kts

Context

UnitTestBot plugin will be working on Java 17 starting from Release 2023.3

[alisevych]

Related issue:

• UtUtils methods using setAccessible doesn't work in Java 17 #2026

[olganaumenko]

@alisevych Please check the Troubleshooting section in Wiki.

[alisevych]

I would correct the following wording not to mess the user:

build an Object assemble model to just build an Object

Also the keys in the first part can be joined into one String so that it can be easily copy-pasted.

[olganaumenko]

@alisevych Please verify the fix.

[alisevych]

We've just identified that adding VM options to Run configuration doesn't work for Gradle run configuration in IDEA.

In case of Gradle project with JDK 17 and a test that uses reflection, the user needs to configure the task that runs this test.
Add VM options to the test task in build.gradle file, like following:

Text to insert:

    jvmArgs += ["--add-opens", "java.base/java.lang=ALL-UNNAMED", 
                "--add-opens", "java.base/java.lang.reflect=ALL-UNNAMED"]

[alisevych]

The list of modules to open can be different.
User needs to open the java modules, which their classes are in.

For example, in OwnerControllerTest in spring-petclinic, there is setFiled called for java.util.LinkedHashMap
The following exception message is in console:

   java.lang.reflect.InaccessibleObjectException: Unable to make field transient java.util.LinkedHashMap$Entry
java.util.LinkedHashMap.head accessible: module java.base does not "opens java.util" to unnamed module ...

So the following string should be added to VM options:
`"--add-opens", "java.base/java.util=ALL-UNNAMED"``