Added test to cover the case where a receipt is required but not provided. (#406)
Added test to cover the case where a receipt is required but not provided. (#406)

* Split the VALID_IS_ADVANCE_CLAIM constant into two constants; IS_FUTURE_CLAIM and IS_PAST_CLAIM to make the tests intention more clear.
* Improved test descriptions.
* Brings test coverage up to 100% for all updated files.
ministryofjustice/apvs-external-web,ministryofjustice/apvs-external-web,ministryofjustice/apvs-external-web