I want to test a failure case which is triggered by a library's non-public exception. How do I throw this exception?

Question

The Tinkerforge library throws TimeoutException and NotConnectedException (among others). I'd like to throw these in my test case, so I can test that my error-handling code works correctly.

When I try

when(brickletLEDStripMock.getRGBValues(any(), any())).thenThrow(new NotConnectedException("Test"));

IntelliJ tells me that the exception is not public and cannot be accessed from outside the package.

Is there a way to throw it anyway, maybe with Powermock?

EDIT:

Thanks to Fran Montero I now got this working code:

Constructor<NotConnectedException> constructor;
constructor = NotConnectedException.class.getDeclaredConstructor();
constructor.setAccessible(true);
NotConnectedException exception = constructor.newInstance();

when(brickletLEDStripMock.getRGBValues(anyInt(), anyShort())).thenThrow(exception);

Maybe you can access the protected class using reflection: http://stackoverflow.com/questions/5629706/java-accessing-private-constructor-with-type-parameters — Fran Montero, Aug 04 '15 at 11:36
That works, thank you! If you want to formulate this as an answer, I'll upvote it :) — Kirby, Aug 04 '15 at 11:58

score 2 · Accepted Answer · edited May 23 '17 at 12:06

2

You can access that class using reflection api:

Constructor<Foo> constructor;
 constructor = Foo.class.getDeclaredConstructor(Object.class);
 constructor.setAccessible(true);
 Foo<String> foo = constructor.newInstance("arg1");

Check Java: accessing private constructor with type parameters

edited May 23 '17 at 12:06

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answered Aug 04 '15 at 12:02

Fran Montero

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I want to test a failure case which is triggered by a library's non-public exception. How do I throw this exception?

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