Assertions
Assertions help a contract developer check progress of a contract along the execution path they are exploring.
Without assertions the contract developer has to verify the state of execution at each step.
With assertions, the developer can verify if a transaction has been spent, is spendable, is confirmed. They can also assert the current chain height, etc.
Assertions are commands that strive to remain intuitive. For example assert_mempool_accept
asserts the transaction argument will be accepted by the mempool.
assert_mempool_accept @alice_tx
All the available assertions are documented under Assertions in the Reference page.