Question

I am testing a function which retries with different parameters on exception. Following is the pseudo code.

class Myclass {
 public void load(input)
  try {
   externalAPI.foo(input);
 } catch(SomeException e) {
   //retry with different parameters
   externalAPI.foo(input,input2);
 }

How can I test above code using junit by mocking externalAPI.

@Test
public void testServiceFailover(){

    m_context.checking(new Expectations() {{
        allowing (mockObjExternalAPI).foo(with(any(String.class)));
        will (throwException(InvalidCustomerException));
        allowing (mockObjExternalAPI).foo(with(any(String.class),with(any(String.class)));
        will (returnValue(mockResult));
    }});
}

But above test fails saying “tried to throw a SomeException from a method(from foo()) that throws no exceptions”. But actually the method foo has mentioned SomeException in its method signature.

How can i write junit for the function foo?

Answer 1

With Mockito, I would do it like this:
…

private ExternalAPI mockExternalAPI;
private MyClass myClass;

@Before
public void executeBeforeEachTestCase()
{
   mockExternalAPI = Mockito.mock(ExternalAPI.class);
   //Throw an exception when mockExternalAPI.foo(String) is called.
   Mockito.doThrow(new SomeException()).when(mockExternalAPI).foo(Mockito.anyString());

   myClass = new MyClass();
   myClass.setExternalAPI(mockExternalAPI); 
} 

@After
public void executeAfterEachTestCase()
{
  mockExternalAPI = null;
  myClass = null;
}

@Test
public void testServiceFailover()
{

   myClass.load("Some string);

   //verify that mockExternalAPI.foo(String,String) was called.
   Mockito.verify(mockExternalAPI).foo(Mockito.anyString(), Mockito.anyString());   
}