Styjun

I have the below interface

public interface Interface1 
 Object Execute(String commandToExecute) throws Exception;

which then I 'm trying to mock so I can test the behaviour of the class that will call it:

Interface1 interfaceMocked = mock(Interface1.class);
when(interfaceMocked.Execute(anyString())).thenThrow(new Exception());
Interface2 objectToTest = new ClassOfInterface2(interfaceMocked);
retrievePrintersMetaData.Retrieve();

But the compiler tells me that there is an unhandled exception.
The definition of the Retrieve method is:

public List<SomeClass> Retrieve() 
 try 
 interface1Object.Execute("");
 
 catch (Exception exception) 
 return new ArrayList<SomeClass>();
 

The mockito documentation only shows uses of RuntimeException, and I have not seen anything on similar on StackOverflow.
I'm using Java 1.7u25 and mockito 1.9.5

Assuming your test method doesn't declare that it throws Exception, the compiler's absolutely right. This line:

when(interfaceMocked.Execute(anyString())).thenThrow(new Exception());

... calls Execute on an instance of Interface1. That can throw Exception, so you either need to catch it or declare that your method throws it.

I would personally recommend just declaring that the test method throws Exception. Nothing else will care about that declaration, and you really don't want to catch it.

You shouldn't be having a problem if your method returns something and throws your error. Now if your method returns void you won't be able to throw an error.

Now the real thing is that you're not testing that your interface throws an exception, instead what you're testing what happens when an exception is thrown within this method.

public List<SomeClass> Retrieve() 
 try 
 interface1Object.Execute("");
 
 catch (Exception exception) 
 return handleException(exception);
 


protected List<SomeClass> handleException(Exception exception) 
 return new ArrayList<SomeClass>();

Then you just call your handleException method and make sure it returns the correct thing. If you need to make sure that your interface is throwing an exception, then that is a different test for your interface class.

It might seem sucky that you are having to make a method for a single line but that's what happens sometimes if you want testable code.

You can use doAnswer method of Mockito to thrown checked exceptions, like this

Mockito.doAnswer(
 invocation -> 
 throw new Exception("It's not bad, it's good");
 )
 .when(interfaceMocked)
 .Execute(org.mockito.ArgumentMatchers.anyString());