Update to ScalaMock 5.1.0 breaks argument matching

[xfyre]

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ScalaMock Version (e.g. 3.5.0)

5.1

Scala Version (e.g. 2.12)

2.12

Runtime (JVM or JS)

JVM

Please describe the expected behavior of the issue

I have a lot of tests where expects or when is called with a stubbed POJO (Hibernate entity class written in Java). All those methods work as expected in the version 4.1.

Please provide a description of what actually happens

After upgrading from 4.1 to 5.1, all tests which have either when or expects with stubbed POJO arguments, are failing with 'unsatisfied expectation' error (as if the method arguments didn't match). I suspected this has something to do with equality tests, but in failing tests debugger never stops in overridden equals method on POJOs.

In theory I can fix that using where predicate, but this will require to rewrite ~ 100 tests - which I would like to avoid.

Reproducible Test Case

This following code will work in 4.1 and fail in 5.1 with "unsatisfied expectation - never called" error on the call to bindAccount.
Note that SystemUser is a Java (not Scala) class (a Hibernate entity).

  "bind device API" should "bind user device" in {
    val payload = new PBindDevice
    payload.token = "token"

    val user = stub[SystemUser]
    (user.getId _).when().returns(1L)

    (authService.getCurrentUser _).expects().returns(user)
    (firebaseService.bindAccount _).expects(user, payload.token).returns()
    (databaseSession.commit _).expects().returns()

    fixture.bindUserDevice(payload)
  }