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I have the following class:
public class MyClass {
private Apple apple;
public void myMethod() {
apple = AppleFactory.createInstance(someStringVariable);
....
....
....
}
}
And the Test class:
@RunWith(MockitoJUnitRunner.class)
public class MyClassTest {
@InjectMocks
MyClass myClass;
@Test
public void myMethod(){
...
...
...
}
}
How could I inject an Apple instance as a mock in MyClass?
312
We can use Mockito class mock() method to create a mock object of a given class or interface. This is the simplest way to mock an object. We are using JUnit 5 to write test cases in conjunction with Mockito to mock objects.
Mockito @InjectMocks annotations allow us to inject mocked dependencies in the annotated class mocked object. This is useful when we have external dependencies in the class we want to mock. We can specify the mock objects to be injected using @Mock or @Spy annotations.
Mock will be created by Mockito. Here we've added two mock method calls, add() and subtract(), to the mock object via when(). However during testing, we've called subtract() before calling add(). When we create a mock object using create(), the order of execution of the method does not matter.
Mocks and stubs are fake Java classes that replace these external dependencies. These fake classes are then instructed before the test starts to behave as you expect. More specifically: A stub is a fake class that comes with preprogrammed return values.
You have 3 possibilities to solve this:
Abstract factory: Instead of using a static method, use a concrete factory class:
public abstract class AppleFactory {
public Apple createInstance(final String str);
}
public class AppleFactoryImpl implements AppleFactory {
public Apple createInstance(final String str) { // Implementation }
}
In your test class, mock the factory:
@RunWith(MockitoJUnitRunner.class)
public class MyClassTest {
@Mock
private AppleFactory appleFactoryMock;
@Mock
private Apple appleMock;
@InjectMocks
MyClass myClass;
@Before
public void setup() {
when(appleFactoryMock.createInstance(Matchers.anyString()).thenReturn(appleMock);
}
@Test
public void myMethod(){
...
...
...
}
}
PowerMock: Use PowerMock to create a mock of a static method. Look at my answer to a relevant question to see how it's done.
Testable class: Make the Apple creation wrapped in a protected method and create a test class that overrides it:
public class MyClass {
private Apple apple;
public void myMethod() {
apple = createApple();
....
....
....
}
protected Apple createApple() {
return AppleFactory.createInstance(someStringVariable);
}
}
@RunWith(MockitoJUnitRunner.class)
public class MyClassTest {
@Mock
private Apple appleMock;
@InjectMocks
MyClass myClass;
@Test
public void myMethod(){
...
...
...
}
private class TestableMyClass extends MyClass {
@Override
public void createApple() {
return appleMock;
}
}
}
Of course, in your test class you should test TestableMyClass and not MyClass.
I'll tell you my opinion on each of the methods:
The abstract factory method is the best one - This is a clear design that hides the implementation details
The testable class - Is the second option which requires minimum changes
PowerMock option is my least favorite - Instead of going for a better design, you ignore and hide your problem. But that's still a valid option.
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