PowerMockito.doNothing() throws Null Pointer Exception

Question

I am mocking ObjectOutputStream void method .writeObject() but it is throwing null pointer exception. How do i mock the void functions using Mockito/PowerMockito.

Class

public class SomeClass {
    public void someMethod() {
        //something
        OtherClass Obj = new OtherClass();
        try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
             ObjectOutputStream oos = new ObjectOutputStream(bos)) {
             oos.writeObject(obj);
             // do something
        } catch (IOException e) {
            //do something
        }
        //something
    }
}

Test Class

@RunWith(PowerMockRunner.class)
@PrepareForTest({
    SomeClass.class
})
public class SomeClassTest {

    @Mock
    private ByteArrayOutputStream byteArrayOutputStreamMock;
    @Mock
    private ObjectOutputStream objectOutputStreamMock;

    @Test
    public void testSomething() {
        MockitoAnnotations.initMocks(this);
        PowerMockito.whenNew(ByteArrayOutputStream.class).withNoArguments().thenReturn(byteArrayOutputStreamMock);
        PowerMockito.whenNew(ObjectOutputStream.class).withArguments(byteArrayOutputStreamMock).thenReturn(objectOutputStreamMock);
        OtherClass otherClass = new OtherClass();
        Mockito.doNothing().when(objectOutputStreamMock).writeObject(otherClass); //This throw null pointer exception.

        // more code
    }
}

Stacktrace

java.lang.NullPointerException
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1108)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Carcigenicate, May 11 '19 at 11:25

score -2 · Answer 1 · answered May 11 '19 at 11:18

-2

objectOutputStreamMock is null. You have to initialize it:

objectOutputStreamMock = Mockito.mock(ObjectOutputStream.class)

answered May 11 '19 at 11:18

matanper

881
8
24

MockitoAnnotations.initMocks(this); initializes that. – TheDominus May 11 '19 at 11:39
@TheDominus my mistake, missed it. try `Mockito.doNothing().when(objectOutputStreamMock).writeObject(Matchers.eq(otherClass))` – matanper May 11 '19 at 17:32

PowerMockito.doNothing() throws Null Pointer Exception

1 Answers1