Spock throw exception test

If you would like to evaluate for instance the message on the thrown Exception, you could do something like:

then:
def e = thrown(CustomException)
e.message == "Some Message"

There could be multiple ways to handle the exception in then:

thrown(CustomException)

or

thrown CustomException

As well we can check if no Exception is thrown in the Test case -

then:

noExceptionThrown()

I believe your then block needs to be fixed. Try the following syntax:

then:
thrown CustomException