TryValues

Trait that provides an implicit conversion that adds success and failure methods to scala.util.Try, enabling you to make assertions about the value of a Success or the exception of a Failure.

The success method will return the Try on which it is invoked as a Success if the Try actually is a Success, or throw TestFailedException if not. The failure method will return the Try on which it is invoked as a Failure if the Try actually is a Failure, or throw TestFailedException if not.

This construct allows you to express in one statement that an Try should be either a Success or a Failure and that its value or exception, respectively,should meet some expectation. Here's an example:

try1.success.value should be > 9
try2.failure.exception should have message "/ by zero"

Or, using assertions instead of a matchers:

assert(try1.success.value > 9)
assert(try2.failure.exception.getMessage == "/ by zero")

Were you to simply invoke get on the Try, if the Try wasn't a Success, it would throw the exception contained in the Failure:

val try2 = Try { 1 / 0 }

try2.get should be < 9 // try2.get throws ArithmeticException

The ArithmeticException would cause the test to fail, but without providing a stack depth pointing to the failing line of test code. This stack depth, provided by TestFailedException (and a few other ScalaTest exceptions), makes it quicker for users to navigate to the cause of the failure. Without TryValues, to get a stack depth exception you would need to make two statements, like this:

try2 should be a 'success // throws TestFailedException
try2.get should be < 9

The TryValues trait allows you to state that more concisely:

try2.success.value should be < 9 // throws TestFailedException