Programming Groovy 2

18.3 Testing for Exceptions

Let’s now look at writing exception tests. We could wrap the method in ​try-catch​. If the method throws the expected exception—that is, if we land in the ​catch​ block—all is well.

If the code does not throw any exceptions, we’ll invoke ​fail​ to indicate the failure of the test, as shown here:

try {
  divide(2, 0)
  fail "Expected ArithmeticException ..."
} catch(ArithmeticException ex) {
  assertTrue true // Success
}

The previous code is Java-style JUnit testing and works with Groovy, as well. However, Groovy makes it easier to write exception tests by providing a method ​shouldFail​ that elegantly wraps up the boilerplate code. Let’s use that to write ...