Mockito "cannot mock this class" error when running multiple tests in single JVM

[shermosa]

The problem

When running tests individually or in Eclipse, they all succeed. When run all together in Maven, Mockito throws this exception: Mockito cannot mock this class: class ___. Mockito can only mock non-private & non-final classes even if the class is non-private (protected), non-final and non-static.

How to reproduce it

1.- Delete this from the pom.xml file

<forkMode>always</forkMode>

2.- Run mvn package in the command line

Stacktrace

[ERROR] com.hotels.mutantswarm.report.ReportTest.testingReport  Time elapsed: 0.014 s  <<< ERROR! 
org.mockito.exceptions.base.MockitoException:  

Mockito cannot mock this class: class com.hotels.mutantswarm.report.Line. 

Mockito can only mock non-private & non-final classes. 
If you're not sure why you're getting this error, please report to the mailing list. 
 

Java              : 1.8 
JVM vendor name    : AdoptOpenJDK 
JVM vendor version : 25.265-b01 
JVM name           : OpenJDK 64-Bit Server VM 
JVM version        : 1.8.0_265-b01 
JVM info           : mixed mode 
OS name            : Mac OS X 
OS version         : 10.15.7


Underlying exception : org.mockito.exceptions.base.MockitoException:  
Cannot create mock for class com.hotels.mutantswarm.report.Line 

The type is not public and its mock class is loaded by a different class loader. 
This can have multiple reasons: 
 - You are mocking a class with additional interfaces of another class loader 
 - Mockito is loaded by a different class loader than the mocked type (e.g. with OSGi) 
 - The thread's context class loader is different than the mock's class loader 
Caused by: org.mockito.exceptions.base.MockitoException:  

Cannot create mock for class com.hotels.mutantswarm.report.Line 

The type is not public and its mock class is loaded by a different class loader. 
This can have multiple reasons: 
 - You are mocking a class with additional interfaces of another class loader 
 - Mockito is loaded by a different class loader than the mocked type (e.g. with OSGi) 
 - The thread's context class loader is different than the mock's class loader