Verify method bug with Maps

[catch441]

Hey,

I think I found a bug with the verify method. It seems that there is some async action behind the method. Here is a sample code with the main problem:

import static org.mockito.Mockito.verify;

import java.util.HashMap;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;

@ExtendWith(MockitoExtension.class)
public class TestClass {

	@Mock
	Validator validator;

	@Test
	public void validateTest() {
		new SomeClass().myMethod(validator);
		verify(validator).validate(new HashMap<String, String>(), "potatoe");
	}
}

import java.util.HashMap;
import java.util.Map;

public class SomeClass {

	public void myMethod (Validator validator) {
		Map<String, String> map = new HashMap<>();
		validator.validate(map, "potatoe");
		map.put("tomatoe", "ketchup");
	}
}

import java.util.Map;

public interface Validator {

	public void validate(Map<String, String> map, String value);
}

Every time I execute the test I get the following message:

Argument(s) are different! Wanted:
validator.validate(
{},
"potatoe"
);
-> at com.ue.economyplayer.logic.impl.TestClass.validateTest(TestClass.java:21)
Actual invocations have different arguments:
validator.validate(
{"tomatoe" = "ketchup"},
"potatoe"
);
-> at com.ue.economyplayer.logic.impl.SomeClass.myMethod(SomeClass.java:10)

at com.ue.economyplayer.logic.impl.TestClass.validateTest(TestClass.java:21)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

The arguments are not matching, but the map is filled after the method invocation and should be empty at the invocation time.

My Environment:

JDK 1.8
JUnit 5
Mockito-Core 3.4.6
Mockito-JUnit-Jupiter 3.4.6

[TimvdLippe]

Does the issue also happen when you remove the .put?

[catch441]

No. After removing the put, the test is working.

[TimvdLippe]

Unfortunately, Map is one of the classes that Mockito relies on internally for its behavior. Stubbing Map will therefore lead to undefined behavior. Additionally, it is advised not to mock classes you don't own: https://github.com/mockito/mockito/wiki/How-to-write-good-tests#dont-mock-a-type-you-dont-own We are working on improving the user experience by working on a DoNotMock feature to avoid mocking classes/methods that are known to crash Mockito internals (#1833). Therefore, I am closing this as "Infeasible". Apologies for the uninformative exception that is thrown.