Mockito Spy doReturn calls original method

Question

I am new to Mockito. I am aware that spy object will never call original method for doReturn, But in my code, which is not happening

import static org.junit.Assert.assertTrue;
import static org.mockito.Matchers.any;
import static org.mockito.Mockito.spy;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.mockito.runners.MockitoJUnitRunner;

class MyClass {
    public int method1(){
        int x =10;
        x = method2(2);
        return x;
    }

    public int method2(int y){
        method3();
        return 20;
    }

    public int method3(){
       return 30;
    }
}

@RunWith(MockitoJUnitRunner.class)
public class Method1Test {
    private MyClass myClass = new MyClass();

    @Before
    public void setup(){}

    @Test
    public void test01(){
        MyClass spyMyClass = spy(myClass);
        doReturn(28).when(spyMyClass).method2(any());
        int a = spyMyClass.method1();
        assertTrue("We did it!!!",a==20);
    }
}

Below is the error stacktrace:

java.lang.NullPointerException at com.Method1Test.test01(Method1Test.java:45) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37) at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:538) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:760) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:460) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:206)
org.mockito.exceptions.misusing.InvalidUseOfMatchersException: 
Misplaced argument matcher detected here:

-> at com.Method1Test.test01(Method1Test.java:45)

Please someone help me out on above and also provide me fix for above issue.

Hello and welcome to Stackoverflow. Can you paste the whole Junit test class (including imports) ? — Guillaume S
What is it you intend to happen? I see that you are stubbing it to return 28 but asserting it will return 20. Which is it you expect? — Dean
@Dean Can you pls tell why iam getting NPE above in stacktrace, any idea? and why does doReturn above calling original method for spy object above? — hari

glytching glytching · Accepted Answer · 2019-01-29T16:34:16

The issue is caused by a type mismatch on the parameter being passed to method2. That's what this part of the exception message is telling you:

org.mockito.exceptions.misusing.InvalidUseOfMatchersException: Misplaced argument matcher detected here:

The following test passes:

@Test
public void test01(){
    MyClass spyMyClass = spy(myClass);
    doReturn(28).when(spyMyClass).method2(anyInt());
    int a = spyMyClass.method1();
    assertTrue("We did it!!!",a==28);
}

There are two changes here:

Use anyInt() instead of any()
Assert that a==28 because you are telling the stub to return 28

Mockito Spy doReturn calls original method

1 Answers