I am trying to mock some reflection based methods. Below you can see the details,
Class Under Test
public class TracerLog {
@AroundInvoke
public Object logCall(InvocationContext context) throws Exception {
Logger logger = new Logger();
String message = "INFO: Invoking method - "
+ context.getMethod().getName() + "() of Class - "
+ context.getMethod().getDeclaringClass();
logger.write(message);
return context.proceed();
}
}
Test
public class TracerLogTest {
@Mock
InvocationContext mockContext;
@Mock
Logger mockLogger;
@InjectMocks
private TracerLog cut = new TracerLog();
@BeforeMethod
public void setup() {
MockitoAnnotations.initMocks(this);
}
@Test
public void logCallTest() throws Exception {
when(mockContext.proceed()).thenReturn(true);
when(mockContext.getMethod().getDeclaringClass().getName()).thenReturn("someClass");
cut.logCall(mockContext);
verify(mockContext).proceed();
}
}
or
@Test
public void logCallTest() throws Exception {
when(mockContext.proceed()).thenReturn(true);
when(mockContext.getMethod().getName()).thenReturn("someMethod");
when(mockContext.getMethod().getDeclaringClass().getName()).thenReturn("someClass");
cut.logCall(mockContext);
verify(mockLogger).write(anyString());
verify(mockContext).proceed();
}
But, the tests fail with a NullPointerException. I understand that I am doing something wrong against mocking concepts, but I do not understand what it is. Could you please throw some light on it and also suggest me how this method can be tested?
Thanks.
Instance mocking means that a statement like: $obj = new \MyNamespace\Foo; …will actually generate a mock object. This is done by replacing the real class with an instance mock (similar to an alias mock), as with mocking public methods.
If we want to access Private Field and method using Reflection we just need to call setAccessible(true) on the field or method object which you want to access. Class. getDeclaredField(String fieldName) or Class. getDeclaredFields() can be used to get private fields.
mock() method with ReturnValues: It allows the creation of mock objects of a given class or interface. Now, it is deprecated, as ReturnValues are replaced with Answer. mock() method with String: It is used to create mock objects by specifying the mock names.
Mockito allows us to partially mock an object. This means that we can create a mock object and still be able to call a real method on it. To call a real method on a mocked object we use Mockito's thenCallRealMethod().
You need a Method object and a Class object. As per your comment, Mockito cannot mock a Method, so you'll need a real one. I haven't tested this, but I believe this would work. Instead of:
when(mockContext.getMethod().getName()).thenReturn("someMethod");
when(mockContext.getMethod().getDeclaringClass().getName()).thenReturn("someClass");
You need:
// any method will do, but here is an example of how to get one.
Method testMethod = this.getClass().getMethod("logCallTest");
when(mockContext.getMethod()).thenReturn(testMethod);
Obviously, getName()
will not return "someMethod" anymore and getDeclaringClass().getName()
will return the name of this test class (in the example), but although you couldn't pick what they return, what they return is still deterministic, so you should be able to verify anything you need. (Of course, if you needed to spy or verify that a call was made on the Method object itself, you're still stuck.)
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