TestBench doesn't work with V14 + Java 16

[tarekoraby]

TestBench doesn't seem to work with the combo of Vaadin version 14 + Java 16.

To reproduce:

Run V14 branch of the skeleton-starter-flow-spring project with Java 16 (tested with Vaadin 14.6.8 + Amazon Correto 16.0.2).

Then execute the tests of MainViewIT. The following errors are observed:

java.lang.IllegalStateException: Unable to create proxy for driver

	at com.vaadin.testbench.TestBench.createDriver(TestBench.java:122)
	at com.vaadin.testbench.TestBench.createDriver(TestBench.java:99)
	at org.vaadin.example.AbstractViewTest.setup(AbstractViewTest.java:58)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.RunBefores.invokeMethod(RunBefores.java:33)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
	at com.vaadin.testbench.parallel.ParallelRunner$1.evaluate(ParallelRunner.java:468)
	at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:61)
	at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:61)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at com.vaadin.testbench.parallel.ParallelScheduler$1.call(ParallelScheduler.java:48)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at java.base/java.lang.Thread.run(Thread.java:831)
Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @396a51ab
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:357)
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
	at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199)
	at java.base/java.lang.reflect.Method.setAccessible(Method.java:193)
	at javassist.util.proxy.SecurityActions.setAccessible(SecurityActions.java:103)
	at javassist.util.proxy.FactoryHelper.toClass2(FactoryHelper.java:181)
	at javassist.util.proxy.FactoryHelper.toClass(FactoryHelper.java:164)
	at javassist.util.proxy.ProxyFactory.createClass3(ProxyFactory.java:507)
	at javassist.util.proxy.ProxyFactory.createClass2(ProxyFactory.java:492)
	at javassist.util.proxy.ProxyFactory.createClass1(ProxyFactory.java:428)
	at javassist.util.proxy.ProxyFactory.createClass(ProxyFactory.java:400)
	at javassist.util.proxy.ProxyFactory.create(ProxyFactory.java:675)
	at javassist.util.proxy.ProxyFactory.create(ProxyFactory.java:660)
	at com.vaadin.testbench.TestBench.createDriver(TestBench.java:116)
	... 25 more

[tarekoraby]

And to clarify, the same tests work just fine with Java 16 on the same machine with Vaadin 20.0.7