How to mock a ObjectProvider<XXX> that is autowired? - spring

Question

I am doing a migration from Spring 4.x to 5.x and am following the recommendation to wrap the object with an ObjectProvider to handle beans that return null: https://stackoverflow.com/a/49393682/10863988
This is the class set up I have:
class ConfigurationClass{
#Autowired
private ObjectProvider<MyObject> myObject;
public SomeOtherClass getSomeOtherClass() {
return new SomeOtherClass(myObject.getIfAvailable());
}
}
class TestSomeOtherClass {
#Mock
MyObject myObject;
#InjectMocks
ConfigurationClass;
SomeOtherClass someOtherClass;
public void setup() {
this.someOtherClass = spy(configuration.getSomeOtherClass());
}
}
The problem is when I run this test. the myObject in the ConfigurationClass returns a null pointer exception.
I've tried adding this to the TestSomeOtherClass but I still can't seem to mock the ObjectProvider<MyObject>:
class TestSomeOtherClass {
#Mock
MyObject myObject;
#Mock
ObjectProvider<MyObject> myObjectObjectProvider;
#InjectMocks
ConfigurationClass;
SomeOtherClass someOtherClass;
public void setup() {
doReturn(myObject).when(myObjectObjectProvider).getIfAvailable();
this.someOtherClass = spy(configuration.getSomeOtherClass());
}
}
Any advice on how to handle this?

Answer 1

You do not tell Mockito to handle it's annotations (#Mock, #InjectMocks) anywhere in your code, so they do not have any effect. By default all non-primitive fields in Java are initialized as null - that's where the NullPointerException comes from.
openMocks/initMocks method
Depending on the version of Mockito you're using, you need to call initMocks() or openMocks() static method from the MockitoAnnotations class:
AutoCloseable openMocks;
#BeforeEach
public void setup() {
// the line below is where the magic happens
openMocks = MockitoAnnotations.openMocks(this);
doReturn(myObject).when(myObjectObjectProvider)
.getIfAvailable();
someOtherClass = spy(configuration.getSomeOtherClass());
}
#AfterEach
void tearDown() throws Exception {
openMocks.close();
}
#Test
void test() {
assertNotNull(someOtherClass);
}
#ExtendWith(MockitoExtension.class)
You can also use the #ExtendWith(MockitoExtension.class) annotation over your class and it has the same effect as the methods described above.
You can find both approaches tested in a GitHub repository I've created (all tests pass).