'Issue with using mockito with mock-maker-inline in Spring boot application

I have a Spring web application that can operate in “special” mode where mockito is used to spy on certain objects. Some of those objects are final (protobuf messages). I know, this may smell like a bad idea but lets say it’s an experiment. When enabling mock-maker-inline extension so final objects can be spied on I’m running into issues that seem to be related to byte buddy and loading some native libraries. When not using extension (and not spying on final classes) everything works as expected. Below is truncated stack trace.

java.lang.IllegalStateException: Could not initialize plugin: interface org.mockito.plugins.MockMaker (alternate: null)
…
Caused by: java.lang.IllegalStateException: Failed to load interface org.mockito.plugins.MockMaker implementation declared in sun.misc.CompoundEnumeration@60cc2b75
…
Caused by: java.lang.reflect.InvocationTargetException
…
Caused by: org.mockito.exceptions.base.MockitoInitializationException:
Could not initialize inline Byte Buddy mock maker.

It appears as if your JDK does not supply a working agent attachment mechanism.
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
…
Caused by: java.lang.IllegalStateException: Error during attachment using: net.bytebuddy.agent.ByteBuddyAgent$AttachmentProvider$Compound@633c165e
…
Caused by: java.lang.reflect.InvocationTargetException
…
Caused by: java.lang.UnsatisfiedLinkError: Native Library /Users/…/.sdkman/candidates/java/8.0.265.hs-adpt/jre/lib/libattach.dylib already loaded in another classloader
mockitobyte-buddy


Solution 1:[1]

This is an unfortunate limitation of JVMs that is solved in Java 9+. In Java 8-, the attachment library can only be bound by a single class loader. It seems as if Byte Buddy and another library attemts a self-attach (maybe EhCache) and bind the virtual machine API.

Can you identify what other library is self-attaching and possibly prevent this?

Solution 2:[2]

In my case the project contained an older version of JMockit 'org.jmockit:jmockit:1.24' which was clashing with mockit-inline. Removing JMockit entirely or upgrading it to 1.49 resolves the problem

https://github.com/mockito/mockito/issues/1879#issuecomment-783326979

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Rafael Winterhalter
Solution 2 Damian Lattenero

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