Mocking a private method in an Expectations block causes "IllegalStateException: Missing invocation to mocked type at this point" - jmockit

Question

I have a JUnit test that uses a JMockit Expectations block:
#Tested
private MyTestedClass myTestedClass;
#Injectable
private MyOtherClass myOtherClass;
#Test
public void publicBooleanMethodTest() {
new Expectations() {{
invoke(myOtherClass, "privateMethod");
result = true;
}};
myTestedClass.run(); // Calls myOtherClass.privateMethod();
}
However, this results in the following error:
java.lang.IllegalStateException: Missing invocation to mocked type at this point; please make sure such invocations appear only after the declaration of a suitable mock field or parameter
As you can see, myClass is mocked via #Injectable, so I'm not sure why the error is happening. I have also found that if I change the scope of privateMethod() to public, everything works.
What is going on and how can I fix this? It worked fine in JMockit 1.22, but now fails in JMockit 1.23 and greater.

Answer 1

JMockit 1.23 removed support for mocking private methods in Expectations blocks. From the release notes:
Version 1.23 (Apr 24, 2016):
Dropped support for the mocking of private methods/constructors when using the Expectations API, to prevent misuse. If still needed, they can be mocked or stubbed out with the application of a MockUp<T>.
Unfortunately, the erroneous error message is currently seen as "too costly too fix" by the development team. A better error message was added in JMockit 1.28 as a result of this discussion.
The error log says to use MockUp<T> as an alternative. In this case, the code would be as follows:
#Tested
private MyTestedClass myTestedClass;
#Injectable
private MyOtherClass myOtherClass;
#Test
public void publicBooleanMethodTest() {
// Partially mock myOtherClass
new MockUp<MyOtherClass>(myOtherClass) {
#Mock boolean privateBooleanMethod() {
return true;
}
};
myTestedClass.run(); // Calls myOtherClass.privateMethod();
}