Unit Testing in Mockito, Calling a chain of functions on an object?

Question

I've not done much testing and very minimal in Mockito. When I call delete on a certain object, I get a DeleteResponse. This has a method called getProcessingErrors() which is a set. I can then call .isEmpty() to see if there are errors or not. I'm trying to mock this out.

DeleteResponse deleteResponse = mock(DeleteResponse.class);

when(catalogFramework.delete(any(DeleteRequest.class))).thenReturn(deleteResponse);

when(deleteResponse.getProcessingErrors()).thenReturn(new HashSet<ProcessingDetails>());

PowerMockito.when(deleteResponse.getProcessingErrors().isEmpty()).thenReturn(true);

Error:

org.mockito.exceptions.misusing.WrongTypeOfReturnValue: 
Boolean cannot be returned by getProcessingErrors()
getProcessingErrors() should return Set
***
If you're unsure why you're getting above error read on.
Due to the nature of the syntax above problem might occur because:
1. This exception *might* occur in wrongly written multi-threaded tests.
   Please refer to Mockito FAQ on limitations of concurrency testing.
2. A spy is stubbed using when(spy.foo()).then() syntax. It is safer to stub spies - 
   - with doReturn|Throw() family of methods. More in javadocs for Mockito.spy() method.

Now, from the way I am reading this, it is saying isEmpty cannot return a boolean, but I believe it's cutting out early and just looking at the getProcessingErrors. How can I fix this?

why are you mocking the actual response and then testing that itself. your test case will always evaluate to true. which class and which method are you testing? — Dhawal Kapil
– Dhawal Kapil, Commented May 4, 2018 at 7:04
Well sometimes I want isEmpty to be true and sometimes I want it to be false. Then I can just throw that one line in each test. No? — John Lippson
– John Lippson, Commented May 4, 2018 at 7:06

Duong Anh · Accepted Answer · 2018-05-04 06:47:39Z

3

You need mock deleteResponse.getProcessingErrors() object before mock isEmpty() function

when(deleteResponse.getProcessingErrors()).thenReturn(mockObject);
PowerMockito.when(mockObject.isEmpty()).thenReturn(true);

answered May 4, 2018 at 6:47

Duong Anh

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Comments

Yogesh Badke · Accepted Answer · 2018-05-04 06:48:52Z

1

In here

when(deleteResponse.getProcessingErrors()).thenReturn(new HashSet<ProcessingDetails>());

PowerMockito.when(deleteResponse.getProcessingErrors().isEmpty()).thenReturn(true);

Either return Set with at least 1 element so that it returns true and you don't need the second line or Mock the HashSet also to return true when isEmpty() is called.

Without HashSet mocking

Set<ProcessingDetails> set = new HashSet<>();
set.add(new ProcessingDetails());
when(deleteResponse.getProcessingErrors()).thenReturn(set);

With HashSet mocking

HashSet<ProcessingDetails> mockedSet = mock(HashSet.class);
when(mockedSet.isEmpty()).thenReturn(true);
when(deleteResponse.getProcessingErrors()).thenReturn(set);

answered May 4, 2018 at 6:48

Yogesh Badke

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Comments

Matthieu Grieger · Accepted Answer · 2018-05-04 07:14:53Z

0

You should be able to use Mockito's RETURNS_DEEP_STUBS to eliminate the need to mock the intermediate object:

DeleteResponse deleteResponse = mock(DeleteResponse.class, RETURNS_DEEP_STUBS);

when(catalogFramework.delete(any(DeleteRequest.class))).thenReturn(deleteResponse);

when(deleteResponse.getProcessingErrors().isEmpty()).thenReturn(true);

Although in this case, using RETURNS_DEEP_STUBS isn't really necessary... you can just initialize an empty HashSet and return it as follows:

when(deleteResponse.getProcessingErrors()).thenReturn(new HashSet<>());

This HashSet is empty, so it will return your desired result of true when calling isEmpty().

edited May 4, 2018 at 7:14

answered May 4, 2018 at 7:09

Matthieu Grieger

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2 Comments

John Lippson Over a year ago

Can this be used in conjunction with PowerMockito?

Matthieu Grieger Over a year ago

Yes, you should be able to use this with PowerMockito in the way I described above.

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