Question

I have a method with some logic and an exception block and would like to test the contents in the exception block.

Method:

Class Validator() {

    protected Validator(blah,blah) {

    }

    protected boolean doStuff(String a, String b) {

        try {
          isValidInput(a){
        } catch (Exception e) {
            b = "unknown error"
        }
    }

test case:

@Test
public void testException() {

Validator testValidator = new testValidator(blah, blah);

        Validator spy = spy(testValidator);
        String var2 = "unknown error"
        doReturn(new Exception()).when(spy.doStuff(var1, var2));

        assertEquals("unknown error", var2);
}

How can I force the real method to go into exception block and continue stubbing?

Answer 1

Firstly, forget about using spy – if isValidInput is able to throw an exception, then make it throw an exception.

If there is a collaborator used within isValidInput() that can throw an Exception, then mock that using Mockito. If it’s just your code, then you should be able to set a such that it will generate an exception.

You still need to write a full set of tests on isValidInput() – investigate using the expected option in the @Test annotation (I assume you’re using JUnit here) to specify that throwing an exception is the expected outcome of the test. But please don’t throw Exception – using a meaningful subclass of it 🙂

And as @Dave Newton commented, testing var2 is never going to work outside the scope of doStuff.